%!PS-Adobe-3.0 %%Creator: Windows PSCRIPT %%Title: Microsoft Word - OPTSYNC.EXP %%BoundingBox: 18 19 593 774 %%DocumentNeededResources: (atend) %%DocumentSuppliedResources: (atend) %%Pages: (atend) %%BeginResource: procset Win35Dict 3 1 /Win35Dict 290 dict def Win35Dict begin/bd{bind def}bind def/in{72 mul}bd/ed{exch def}bd/ld{load def}bd/tr/translate ld/gs/gsave ld/gr /grestore ld/M/moveto ld/L/lineto ld/rmt/rmoveto ld/rlt/rlineto ld /rct/rcurveto ld/st/stroke ld/n/newpath ld/sm/setmatrix ld/cm/currentmatrix ld/cp/closepath ld/ARC/arcn ld/TR{65536 div}bd/lj/setlinejoin ld/lc /setlinecap ld/ml/setmiterlimit ld/sl/setlinewidth ld/scignore false def/sc{scignore{pop pop pop}{0 index 2 index eq 2 index 4 index eq and{pop pop 255 div setgray}{3{255 div 3 1 roll}repeat setrgbcolor}ifelse}ifelse}bd /FC{bR bG bB sc}bd/fC{/bB ed/bG ed/bR ed}bd/HC{hR hG hB sc}bd/hC{ /hB ed/hG ed/hR ed}bd/PC{pR pG pB sc}bd/pC{/pB ed/pG ed/pR ed}bd/sM matrix def/PenW 1 def/iPen 5 def/mxF matrix def/mxE matrix def/mxUE matrix def/mxUF matrix def/fBE false def/iDevRes 72 0 matrix defaultmatrix dtransform dup mul exch dup mul add sqrt def/fPP false def/SS{fPP{ /SV save def}{gs}ifelse}bd/RS{fPP{SV restore}{gr}ifelse}bd/EJ{gsave showpage grestore}bd/#C{userdict begin/#copies ed end}bd/FEbuf 2 string def/FEglyph(G )def/FE{1 exch{dup 16 FEbuf cvrs FEglyph exch 1 exch putinterval 1 index exch FEglyph cvn put}for}bd/SM{/iRes ed/cyP ed /cxPg ed/cyM ed/cxM ed 72 100 div dup scale dup 0 ne{90 eq{cyM exch 0 eq{cxM exch tr -90 rotate -1 1 scale}{cxM cxPg add exch tr +90 rotate}ifelse}{cyP cyM sub exch 0 ne{cxM exch tr -90 rotate}{cxM cxPg add exch tr -90 rotate 1 -1 scale}ifelse}ifelse}{pop cyP cyM sub exch 0 ne{cxM cxPg add exch tr 180 rotate}{cxM exch tr 1 -1 scale}ifelse}ifelse 100 iRes div dup scale 0 0 transform .25 add round .25 sub exch .25 add round .25 sub exch itransform translate}bd/SJ{1 index 0 eq{pop pop/fBE false def}{1 index/Break ed div/dxBreak ed/fBE true def}ifelse}bd/ANSIVec[ 16#0/grave 16#1/acute 16#2/circumflex 16#3/tilde 16#4/macron 16#5/breve 16#6/dotaccent 16#7/dieresis 16#8/ring 16#9/cedilla 16#A/hungarumlaut 16#B/ogonek 16#C/caron 16#D/dotlessi 16#27/quotesingle 16#60/grave 16#7C/bar 16#82/quotesinglbase 16#83/florin 16#84/quotedblbase 16#85 /ellipsis 16#86/dagger 16#87/daggerdbl 16#88/circumflex 16#89/perthousand 16#8A/Scaron 16#8B/guilsinglleft 16#8C/OE 16#91/quoteleft 16#92/quoteright 16#93/quotedblleft 16#94/quotedblright 16#95/bullet 16#96/endash 16#97 /emdash 16#98/tilde 16#99/trademark 16#9A/scaron 16#9B/guilsinglright 16#9C/oe 16#9F/Ydieresis 16#A0/space 16#A1/exclamdown 16#A4/currency 16#A5/yen 16#A6/brokenbar 16#A7/section 16#A8/dieresis 16#A9/copyright 16#AA/ordfeminine 16#AB/guillemotleft 16#AC/logicalnot 16#AD/hyphen 16#AE/registered 16#AF/macron 16#B0/degree 16#B1/plusminus 16#B2/twosuperior 16#B3/threesuperior 16#B4/acute 16#B5/mu 16#B6/paragraph 16#B7/periodcentered 16#B8/cedilla 16#B9/onesuperior 16#BA/ordmasculine 16#BB/guillemotright 16#BC/onequarter 16#BD/onehalf 16#BE/threequarters 16#BF/questiondown 16#C0/Agrave 16#C1/Aacute 16#C2/Acircumflex 16#C3/Atilde 16#C4/Adieresis 16#C5/Aring 16#C6/AE 16#C7/Ccedilla 16#C8/Egrave 16#C9/Eacute 16#CA /Ecircumflex 16#CB/Edieresis 16#CC/Igrave 16#CD/Iacute 16#CE/Icircumflex 16#CF/Idieresis 16#D0/Eth 16#D1/Ntilde 16#D2/Ograve 16#D3/Oacute 16#D4 /Ocircumflex 16#D5/Otilde 16#D6/Odieresis 16#D7/multiply 16#D8/Oslash 16#D9/Ugrave 16#DA/Uacute 16#DB/Ucircumflex 16#DC/Udieresis 16#DD/Yacute 16#DE/Thorn 16#DF/germandbls 16#E0/agrave 16#E1/aacute 16#E2/acircumflex 16#E3/atilde 16#E4/adieresis 16#E5/aring 16#E6/ae 16#E7/ccedilla 16#E8 /egrave 16#E9/eacute 16#EA/ecircumflex 16#EB/edieresis 16#EC/igrave 16#ED/iacute 16#EE/icircumflex 16#EF/idieresis 16#F0/eth 16#F1/ntilde 16#F2/ograve 16#F3/oacute 16#F4/ocircumflex 16#F5/otilde 16#F6/odieresis 16#F7/divide 16#F8/oslash 16#F9/ugrave 16#FA/uacute 16#FB/ucircumflex 16#FC/udieresis 16#FD/yacute 16#FE/thorn 16#FF/ydieresis ] def/reencdict 12 dict def/IsChar{basefontdict/CharStrings get exch known}bd/MapCh{dup IsChar not{pop/bullet}if newfont/Encoding get 3 1 roll put}bd/MapDegree{16#b0 /degree IsChar{/degree}{/ring}ifelse MapCh}bd/MapBB{16#a6/brokenbar IsChar{/brokenbar}{/bar}ifelse MapCh}bd/ANSIFont{reencdict begin/newfontname ed/basefontname ed FontDirectory newfontname known not{/basefontdict basefontname findfont def/newfont basefontdict maxlength dict def basefontdict{exch dup/FID ne{dup/Encoding eq{exch dup length array copy newfont 3 1 roll put}{exch newfont 3 1 roll put}ifelse}{pop pop}ifelse}forall newfont /FontName newfontname put 127 1 159{newfont/Encoding get exch/bullet put}for ANSIVec aload pop ANSIVec length 2 idiv{MapCh}repeat MapDegree MapBB newfontname newfont definefont pop}if newfontname end}bd/SB{FC /ULlen ed/str ed str length fBE not{dup 1 gt{1 sub}if}if/cbStr ed /dxGdi ed/y0 ed/x0 ed str stringwidth dup 0 ne{/y1 ed/x1 ed y1 y1 mul x1 x1 mul add sqrt dxGdi exch div 1 sub dup x1 mul cbStr div exch y1 mul cbStr div}{exch abs neg dxGdi add cbStr div exch}ifelse/dyExtra ed/dxExtra ed x0 y0 M fBE{dxBreak 0 BCh dxExtra dyExtra str awidthshow}{dxExtra dyExtra str ashow}ifelse fUL{x0 y0 M dxUL dyUL rmt ULlen fBE{Break add}if 0 mxUE transform gs rlt cyUL sl [] 0 setdash st gr}if fSO{x0 y0 M dxSO dySO rmt ULlen fBE{Break add}if 0 mxUE transform gs rlt cyUL sl [] 0 setdash st gr}if n/fBE false def}bd/font{/name ed/Ascent ed 0 ne/fT3 ed 0 ne/fSO ed 0 ne/fUL ed/Sy ed/Sx ed 10.0 div/ori ed -10.0 div/esc ed/BCh ed name findfont/xAscent 0 def/yAscent Ascent def/ULesc esc def ULesc mxUE rotate pop fT3{/esc 0 def xAscent yAscent mxUE transform /yAscent ed/xAscent ed}if [Sx 0 0 Sy neg xAscent yAscent] esc mxE rotate mxF concatmatrix makefont setfont [Sx 0 0 Sy neg 0 Ascent] mxUE mxUF concatmatrix pop fUL{currentfont dup/FontInfo get/UnderlinePosition known not{pop/Courier findfont}if/FontInfo get/UnderlinePosition get 1000 div 0 exch mxUF transform/dyUL ed/dxUL ed}if fSO{0 .3 mxUF transform /dySO ed/dxSO ed}if fUL fSO or{currentfont dup/FontInfo get/UnderlineThickness known not{pop/Courier findfont}if/FontInfo get/UnderlineThickness get 1000 div Sy mul/cyUL ed}if}bd/min{2 copy gt{exch}if pop}bd/max{2 copy lt{exch}if pop}bd/CP{/ft ed{{ft 0 eq{clip}{eoclip}ifelse}stopped{currentflat 1 add setflat}{exit}ifelse}loop}bd/patfont 10 dict def patfont begin /FontType 3 def/FontMatrix [1 0 0 -1 0 0] def/FontBBox [0 0 16 16] def/Encoding StandardEncoding def/BuildChar{pop pop 16 0 0 0 16 16 setcachedevice 16 16 false [1 0 0 1 .25 .25]{pat}imagemask}bd end/p{ /pat 32 string def{}forall 0 1 7{dup 2 mul pat exch 3 index put dup 2 mul 1 add pat exch 3 index put dup 2 mul 16 add pat exch 3 index put 2 mul 17 add pat exch 2 index put pop}for}bd/pfill{/PatFont patfont definefont setfont/ch(AAAA)def X0 64 X1{Y1 -16 Y0{1 index exch M ch show}for pop}for}bd/vert{X0 w X1{dup Y0 M Y1 L st}for}bd/horz{Y0 w Y1{dup X0 exch M X1 exch L st}for}bd/fdiag{X0 w X1{Y0 M X1 X0 sub dup rlt st}for Y0 w Y1{X0 exch M Y1 Y0 sub dup rlt st}for}bd/bdiag{X0 w X1{Y1 M X1 X0 sub dup neg rlt st}for Y0 w Y1{X0 exch M Y1 Y0 sub dup neg rlt st}for}bd/AU{1 add cvi 15 or}bd/AD{1 sub cvi -16 and}bd/SHR{pathbbox AU/Y1 ed AU/X1 ed AD/Y0 ed AD/X0 ed}bd/hfill{/w iRes 37.5 div round def 0.1 sl [] 0 setdash n dup 0 eq{horz}if dup 1 eq{vert}if dup 2 eq{fdiag}if dup 3 eq{bdiag}if dup 4 eq{horz vert}if 5 eq{fdiag bdiag}if}bd/F{/ft ed fm 256 and 0 ne{gs FC ft 0 eq{fill}{eofill}ifelse gr}if fm 1536 and 0 ne{SHR gs HC ft CP fm 1024 and 0 ne{/Tmp save def pfill Tmp restore}{fm 15 and hfill}ifelse gr}if}bd/S{PenW sl PC st}bd/m matrix def/GW{iRes 12 div PenW add cvi}bd/DoW{iRes 50 div PenW add cvi}bd/DW{iRes 8 div PenW add cvi}bd/SP{/PenW ed/iPen ed iPen 0 eq iPen 6 eq or{[] 0 setdash}if iPen 1 eq{[DW GW] 0 setdash}if iPen 2 eq{[DoW GW] 0 setdash}if iPen 3 eq{[DW GW DoW GW] 0 setdash}if iPen 4 eq{[DW GW DoW GW DoW GW] 0 setdash}if}bd/E{m cm pop tr scale 1 0 moveto 0 0 1 0 360 arc cp m sm}bd /AG{/sy ed/sx ed 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dx neg 0 rlt cp}bd /CB{B clip n}bd/ErrHandler{errordict dup maxlength exch length gt dup{errordict begin}if/errhelpdict 12 dict def errhelpdict begin/stackunderflow(operand stack underflow)def /undefined(this name is not defined in a dictionary)def/VMerror(you have used up all the printer's memory)def /typecheck(operator was expecting a different type of operand)def /ioerror(input/output error occured)def end{end}if errordict begin /handleerror{$error begin newerror{/newerror false def showpage 72 72 scale/x .25 def/y 9.6 def/Helvetica findfont .2 scalefont setfont x y moveto(Offending Command = )show/command load{dup type/stringtype ne{(max err string)cvs}if show}exec/y y .2 sub def x y moveto(Error = )show errorname{dup type dup( max err string )cvs show( : )show/stringtype ne{( max err string )cvs}if show}exec errordict begin errhelpdict errorname known{x 1 add y .2 sub moveto errhelpdict errorname get show}if end /y y .4 sub def x y moveto(Stack =)show ostack{/y y .2 sub def x 1 add y moveto dup type/stringtype ne{( max err string )cvs}if show}forall showpage}if end}def end}bd end %%EndResource /SVDoc save def %%EndProlog %%BeginSetup Win35Dict begin ErrHandler statusdict begin 0 setjobtimeout end statusdict begin statusdict /jobname (Microsoft Word - OPTSYNC.EXP) put end /oldDictCnt countdictstack def {statusdict begin 0 setpapertray end }stopped { countdictstack oldDictCnt lt { Win35Dict begin } {1 1 countdictstack oldDictCnt sub {pop end } for } ifelse } if /oldDictCnt countdictstack def {letter }stopped { countdictstack oldDictCnt lt { Win35Dict begin } {1 1 countdictstack oldDictCnt sub {pop end } for } ifelse } if [{} /exec load currenttransfer /exec load] cvx settransfer %%EndSetup %%Page: 1 1 %%PageResources: (atend) SS 0 0 25 25 798 1100 300 SM 32 0 0 58 58 0 0 0 54 /Palatino-Roman /font27 ANSIFont font 0 0 0 fC 561 225 1278 (Experiences With Optimistic Synchronization For) 1278 SB 801 295 798 (Distributed Operating Systems) 798 SB 32 0 0 50 50 0 0 0 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84 (that ) 87 SB 765 1588 121 (might ) 124 SB 889 1588 114 (cause ) 117 SB 1006 1588 310 (synchronization ) 313 SB 1319 1588 186 (problems ) 189 SB 1508 1588 96 (with ) 99 SB 1607 1588 109 (other ) 112 SB 1719 1588 220 (processors, ) 223 SB 1942 1588 37 (it ) 40 SB 1982 1588 118 (blocks) 118 SB 300 1639 98 (until ) 106 SB 406 1639 37 (it ) 45 SB 451 1639 75 (can ) 83 SB 534 1639 54 (be ) 63 SB 597 1639 138 (certain ) 147 SB 744 1639 84 (that ) 93 SB 837 1639 58 (no ) 67 SB 904 1639 97 (such ) 106 SB 1010 1639 186 (problems ) 195 SB 1205 1639 82 (will ) 91 SB 1296 1639 110 (arise. ) 119 SB 1415 1639 11 ( ) 20 SB 1435 1639 118 (There ) 127 SB 1562 1639 69 (are ) 78 SB 1640 1639 116 (many ) 125 SB 1765 1639 172 (different ) 181 SB 1946 1639 108 (ways ) 117 SB 2063 1639 37 (to) 37 SB 300 1690 151 (achieve ) 152 SB 452 1690 310 (synchronization ) 311 SB 763 1690 113 (using ) 114 SB 877 1690 181 (blocking, ) 182 SB 1059 1690 73 (but ) 75 SB 1134 1690 56 (all ) 58 SB 1192 1690 48 (of ) 50 SB 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SB 1605 1893 191 (processor ) 196 SB 1801 1893 95 (goes ) 100 SB 1901 1893 123 (ahead ) 128 SB 2029 1893 71 (and) 71 SB 300 1944 182 (performs ) 184 SB 484 1944 69 (the ) 72 SB 556 1944 135 (action. ) 138 SB 694 1944 11 ( ) 14 SB 708 1944 49 (In ) 52 SB 760 1944 109 (some ) 112 SB 872 1944 118 (cases, ) 121 SB 993 1944 223 (performing ) 226 SB 1219 1944 69 (the ) 72 SB 1291 1944 124 (action ) 127 SB 1418 1944 245 (immediately ) 248 SB 1666 1944 41 (is ) 44 SB 1710 1944 175 (perfectly ) 178 SB 1888 1944 95 (safe. ) 98 SB 1986 1944 11 ( ) 14 SB 2000 1944 39 (If ) 42 SB 2042 1944 58 (the) 58 SB 300 1995 191 (processor ) 200 SB 500 1995 82 (had ) 91 SB 591 1995 139 (waited ) 148 SB 739 1995 48 (to ) 57 SB 796 1995 128 (obtain ) 138 SB 934 1995 310 (synchronization ) 320 SB 1254 1995 243 (information, ) 253 SB 1507 1995 157 (instead, ) 167 SB 1674 1995 37 (it ) 47 SB 1721 1995 132 (would ) 142 SB 1863 1995 100 (have ) 110 SB 1973 1995 127 (simply) 127 SB 300 2046 850 (wasted its time until 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225 106 (them ) 107 SB 1614 225 82 (inde) 82 SB 1696 225 199 (pendently ) 200 SB 1896 225 48 (of ) 49 SB 1945 225 56 (all ) 57 SB 2002 225 98 (other) 98 SB 300 276 220 (processors. ) 222 SB 522 276 11 ( ) 13 SB 535 276 81 (The ) 83 SB 618 276 134 (TWOS ) 136 SB 754 276 192 (scheduler ) 194 SB 948 276 141 (always ) 143 SB 1091 276 156 (chooses ) 158 SB 1249 276 69 (the ) 71 SB 1320 276 98 (local ) 100 SB 1420 276 120 (object ) 122 SB 1542 276 96 (with ) 99 SB 1641 276 56 (an ) 59 SB 1700 276 114 (unpro) 114 SB 1814 276 132 (cessed ) 135 SB 1949 276 113 (event ) 116 SB 2065 276 35 (at) 35 SB 300 327 69 (the ) 76 SB 376 327 145 (earliest ) 152 SB 528 327 209 (simulation ) 216 SB 744 327 94 (time ) 101 SB 845 327 48 (to ) 55 SB 900 327 77 (run ) 84 SB 984 327 102 (next. ) 109 SB 1093 327 11 ( ) 18 SB 1111 327 108 (Since ) 115 SB 1226 327 146 (TWOS\222 ) 153 SB 1379 327 90 (goal ) 97 SB 1476 327 41 (is ) 48 SB 1524 327 78 (fast ) 86 SB 1610 327 220 (completion ) 228 SB 1838 327 48 (of ) 56 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running.) 1722 SB 300 581 108 (Since ) 109 SB 409 581 95 (each ) 96 SB 505 581 191 (processor ) 192 SB 697 581 193 (schedules ) 194 SB 891 581 158 (without ) 159 SB 1050 581 152 (waiting ) 154 SB 1204 581 76 (for, ) 78 SB 1282 581 51 (or ) 53 SB 1335 581 66 (con) 66 SB 1401 581 69 (sult) 69 SB 1470 581 70 (ing ) 72 SB 1542 581 107 (with, ) 109 SB 1651 581 109 (other ) 111 SB 1762 581 220 (processors, ) 222 SB 1984 581 46 (at ) 48 SB 2032 581 68 (any) 68 SB 300 632 114 (given ) 119 SB 419 632 138 (instant ) 143 SB 562 632 48 (of ) 53 SB 615 632 81 (real ) 86 SB 701 632 94 (time ) 99 SB 800 632 69 (the ) 75 SB 875 632 171 (system\222s ) 177 SB 1052 632 209 (processors ) 215 SB 1267 632 92 (may ) 98 SB 1365 632 54 (be ) 60 SB 1425 632 168 (working ) 174 SB 1599 632 46 (at ) 52 SB 1651 632 32 (a ) 38 SB 1689 632 104 (wide ) 110 SB 1799 632 116 (range ) 122 SB 1921 632 48 (of ) 54 SB 1975 632 125 (virtual) 125 SB 300 683 123 (times. ) 124 SB 424 683 11 ( ) 12 SB 436 683 68 (An ) 69 SB 505 683 120 (object ) 122 SB 627 683 160 (running ) 162 SB 789 683 46 (at ) 48 SB 837 683 32 (a ) 34 SB 871 683 81 (low ) 83 SB 954 683 136 (virtual ) 138 SB 1092 683 94 (time ) 96 SB 1188 683 75 (can ) 77 SB 1265 683 99 (send ) 101 SB 1366 683 32 (a ) 34 SB 1400 683 168 (message ) 170 SB 1570 683 48 (to ) 50 SB 1620 683 154 (another ) 156 SB 1776 683 120 (object ) 122 SB 1898 683 46 (at ) 48 SB 1946 683 32 (a ) 34 SB 1980 683 120 (higher) 120 SB 300 734 136 (virtual ) 141 SB 441 734 105 (time. ) 110 SB 551 734 11 ( ) 16 SB 567 734 39 (If ) 44 SB 611 734 69 (the ) 74 SB 685 734 168 (message ) 173 SB 858 734 41 (is ) 46 SB 904 734 201 (scheduled ) 206 SB 1110 734 48 (to ) 53 SB 1163 734 122 (arrive ) 127 SB 1290 734 46 (at ) 51 SB 1341 734 32 (a ) 37 SB 1378 734 136 (virtual ) 141 SB 1519 734 94 (time ) 99 SB 1618 734 130 (earlier ) 136 SB 1754 734 94 (than ) 100 SB 1854 734 69 (the ) 75 SB 1929 734 171 (receiving) 171 SB 300 786 120 (object ) 125 SB 425 786 41 (is ) 46 SB 471 786 182 (currently ) 188 SB 659 786 188 (handling, ) 194 SB 853 786 69 (the ) 75 SB 928 786 160 (receiver ) 166 SB 1094 786 105 (must ) 111 SB 32 0 0 42 42 0 0 0 40 /Palatino-Italic /font26 ANSIFont font 1205 785 70 (roll ) 76 SB 1281 785 74 (back) 74 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 1355 786 11 ( ) 17 SB 1372 786 65 (his ) 71 SB 1443 786 248 (computation ) 254 SB 1697 786 48 (to ) 54 SB 1751 786 69 (the ) 75 SB 1826 786 136 (virtual ) 142 SB 1968 786 132 (receive) 132 SB 300 837 94 (time ) 95 SB 395 837 48 (of ) 49 SB 444 837 69 (the ) 70 SB 514 837 125 (newly ) 126 SB 640 837 148 (arrived ) 149 SB 789 837 179 (message. ) 180 SB 969 837 11 ( ) 12 SB 981 837 91 (Any ) 92 SB 1073 837 198 (erroneous ) 200 SB 1273 837 109 (work ) 111 SB 1384 837 104 (done ) 106 SB 1490 837 57 (by ) 59 SB 1549 837 69 (the ) 71 SB 1620 837 241 (out-of-order ) 243 SB 1863 837 237 (computation) 237 SB 300 888 105 (must ) 106 SB 406 888 54 (be ) 55 SB 461 888 130 (totally ) 131 SB 592 888 164 (undone. ) 165 SB 757 888 11 ( ) 12 SB 769 888 176 (Undoing ) 177 SB 946 888 69 (the ) 71 SB 1017 888 198 (erroneous ) 200 SB 1217 888 109 (work ) 111 SB 1328 888 164 (requires ) 166 SB 1494 888 183 (throwing ) 185 SB 1679 888 111 (away ) 113 SB 1792 888 98 (local ) 100 SB 1892 888 135 (results ) 137 SB 2029 888 71 (and) 71 SB 300 939 158 (sending ) 160 SB 460 939 168 (message ) 170 SB 630 939 250 (cancellations ) 252 SB 882 939 48 (to ) 50 SB 932 939 109 (other ) 111 SB 1043 939 149 (objects. ) 151 SB 1194 939 11 ( ) 13 SB 1207 939 134 (TWOS ) 136 SB 1343 939 41 (is ) 43 SB 1386 939 87 (able ) 89 SB 1475 939 48 (to ) 50 SB 1525 939 175 (correctly ) 177 SB 1702 939 109 (undo ) 111 SB 1813 939 79 (any ) 82 SB 1895 939 109 (work ) 112 SB 2007 939 93 (done) 93 SB 300 990 120 (prema) 120 SB 420 990 133 (turely, ) 145 SB 565 990 114 (along ) 126 SB 691 990 96 (with ) 108 SB 799 990 79 (any ) 91 SB 890 990 87 (side ) 99 SB 989 990 130 (effects ) 142 SB 1131 990 37 (it ) 49 SB 1180 990 92 (may ) 104 SB 1284 990 100 (have ) 113 SB 1397 990 93 (had. ) 106 SB 1503 990 11 ( ) 24 SB 1527 990 134 (TWOS ) 147 SB 1674 990 64 (roll) 64 SB 1738 990 97 (back ) 110 SB 1848 990 82 (and ) 95 SB 1943 990 157 (message) 157 SB 300 1041 841 (cancellation is totally transparent to the appli) 841 SB 1141 1041 298 (cation program.) 298 SB 300 1143 121 (Every ) 123 SB 423 1143 120 (object ) 122 SB 545 1143 74 (has ) 76 SB 621 1143 32 (a ) 34 SB 655 1143 63 (set ) 65 SB 720 1143 48 (of ) 50 SB 770 1143 144 (private ) 146 SB 916 1143 179 (variables ) 181 SB 1097 1143 121 (called ) 123 SB 1220 1143 55 (its ) 57 SB 32 0 0 42 42 0 0 0 40 /Palatino-Italic /font26 ANSIFont font 1277 1142 79 (state) 79 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 1356 1143 22 (, ) 24 SB 1380 1143 125 (which ) 127 SB 1507 1143 136 (cannot ) 138 SB 1645 1143 54 (be ) 56 SB 1701 1143 154 (directly ) 157 SB 1858 1143 193 (examined ) 196 SB 2054 1143 46 (by) 46 SB 300 1194 79 (any ) 84 SB 384 1194 109 (other ) 114 SB 498 1194 131 (object. ) 136 SB 634 1194 11 ( ) 16 SB 650 1194 121 (Every ) 126 SB 776 1194 113 (event ) 118 SB 894 1194 132 (causes ) 137 SB 1031 1194 69 (the ) 74 SB 1105 1194 161 (creation ) 166 SB 1271 1194 48 (of ) 53 SB 1324 1194 32 (a ) 37 SB 1361 1194 90 (new ) 96 SB 1457 1194 149 (version ) 155 SB 1612 1194 48 (of ) 54 SB 1666 1194 69 (the ) 75 SB 1741 1194 109 (state, ) 115 SB 1856 1194 244 (timestamped) 244 SB 300 1245 96 (with ) 101 SB 401 1245 69 (the ) 74 SB 475 1245 209 (simulation ) 214 SB 689 1245 94 (time ) 99 SB 788 1245 48 (of ) 53 SB 841 1245 69 (the ) 74 SB 915 1245 124 (event. ) 129 SB 1044 1245 11 ( ) 16 SB 1060 1245 134 (TWOS ) 139 SB 1199 1245 172 (typically ) 177 SB 1376 1245 117 (keeps ) 122 SB 1498 1245 168 (multiple ) 174 SB 1672 1245 128 (copies ) 134 SB 1806 1245 48 (of ) 54 SB 1860 1245 95 (each ) 101 SB 1961 1245 139 (object\222s) 139 SB 300 1296 98 (state ) 107 SB 407 1296 47 (in ) 57 SB 464 1296 114 (order ) 124 SB 588 1296 48 (to ) 58 SB 646 1296 158 (support ) 168 SB 814 1296 172 (rollback. ) 182 SB 996 1296 11 ( ) 21 SB 1017 1296 172 (Rollback ) 182 SB 1199 1296 132 (causes ) 142 SB 1341 1296 79 (any ) 89 SB 1430 1296 176 (incorrect ) 186 SB 1616 1296 128 (copies ) 138 SB 1754 1296 48 (of ) 58 SB 1812 1296 69 (the ) 79 SB 1891 1296 98 (state ) 108 SB 1999 1296 48 (to ) 58 SB 2057 1296 43 (be) 43 SB 300 1347 1068 (deleted, and restores one of the earlier copies of the state.) 1068 SB 300 1448 171 (Message ) 173 SB 473 1448 232 (cancellation ) 234 SB 707 1448 47 (in ) 49 SB 756 1448 134 (TWOS ) 136 SB 892 1448 41 (is ) 43 SB 935 1448 210 (performed ) 212 SB 1147 1448 57 (by ) 60 SB 1207 1448 161 (creating ) 164 SB 1371 1448 83 (two ) 86 SB 1457 1448 128 (copies ) 131 SB 1588 1448 48 (of ) 51 SB 1639 1448 95 (each ) 98 SB 1737 1448 168 (message ) 171 SB 1908 1448 98 (sent. ) 101 SB 2009 1448 11 ( ) 14 SB 2023 1448 77 (One) 77 SB 300 1500 112 (copy, ) 115 SB 415 1500 121 (called ) 124 SB 539 1500 69 (the ) 72 SB 32 0 0 42 42 0 0 0 40 /Palatino-Italic /font26 ANSIFont font 611 1499 142 (positive ) 145 SB 756 1499 78 (copy) 78 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 834 1500 22 (, ) 25 SB 859 1500 41 (is ) 44 SB 903 1500 87 (sent ) 90 SB 993 1500 48 (to ) 51 SB 1044 1500 69 (the ) 72 SB 1116 1500 182 (receiving ) 185 SB 1301 1500 131 (object. ) 134 SB 1435 1500 11 ( ) 14 SB 1449 1500 81 (The ) 84 SB 1533 1500 109 (other ) 112 SB 1645 1500 112 (copy, ) 115 SB 1760 1500 121 (called ) 125 SB 1885 1500 69 (the ) 73 SB 32 0 0 42 42 0 0 0 40 /Palatino-Italic /font26 ANSIFont font 1958 1499 142 (negative) 142 SB 300 1551 78 (copy) 78 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 378 1552 1391 (, is retained by the sender. Should cancellation of a message be necessary, ) 1392 SB 1770 1552 69 (the ) 70 SB 1840 1552 169 (negative ) 170 SB 2010 1552 90 (copy) 90 SB 300 1603 41 (is ) 51 SB 351 1603 87 (sent ) 97 SB 448 1603 48 (to ) 58 SB 506 1603 69 (the ) 79 SB 585 1603 171 (receiver. ) 181 SB 766 1603 11 ( ) 21 SB 787 1603 121 (When ) 131 SB 918 1603 69 (the ) 79 SB 997 1603 160 (receiver ) 171 SB 1168 1603 92 (tries ) 103 SB 1271 1603 48 (to ) 59 SB 1330 1603 169 (enqueue ) 180 SB 1510 1603 48 (it, ) 59 SB 1569 1603 134 (TWOS ) 145 SB 1714 1603 208 (recognizes ) 219 SB 1933 1603 84 (that ) 95 SB 2028 1603 72 (two) 72 SB 300 1655 197 (messages, ) 199 SB 499 1655 171 (identical ) 173 SB 672 1655 131 (except ) 133 SB 805 1655 65 (for ) 67 SB 872 1655 98 (their ) 101 SB 973 1655 99 (sign, ) 102 SB 1075 1655 69 (are ) 72 SB 1147 1655 47 (in ) 50 SB 1197 1655 69 (the ) 72 SB 1269 1655 107 (same ) 110 SB 1379 1655 136 (queue. ) 139 SB 1518 1655 11 ( ) 14 SB 1532 1655 81 (The ) 84 SB 1616 1655 168 (message ) 171 SB 1787 1655 128 (copies ) 131 SB 32 0 0 42 42 0 0 0 40 /Palatino-Italic /font26 ANSIFont font 1918 1654 171 (annihilate) 171 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 2089 1655 11 (,) 11 SB 300 1706 82 (and ) 84 SB 384 1706 69 (the ) 71 SB 455 1706 160 (receiver ) 162 SB 617 1706 93 (rolls ) 95 SB 712 1706 97 (back ) 99 SB 811 1706 69 (the ) 71 SB 882 1706 113 (event ) 115 SB 997 1706 203 (associated ) 205 SB 1202 1706 96 (with ) 98 SB 1300 1706 69 (the ) 71 SB 1371 1706 159 (positive ) 161 SB 1532 1706 112 (copy, ) 114 SB 1646 1706 37 (if ) 39 SB 1685 1706 69 (the ) 71 SB 1756 1706 113 (event ) 116 SB 1872 1706 85 (was ) 88 SB 1960 1706 140 (already) 140 SB 300 1757 210 (performed.) 210 SB 1 lc 1 lj 0 0 0 pC 6 4 SP 255 255 255 fC /fm 256 def 1185 2039 1484 2288 56 56 RR 1 F S n 0 lc 0 lj /fm 256 def 449 99 735 2114 B 1 F S n 1 lc 1 lj gs 8 100 879 2112 CB 883 2012 M 0 300 1 PP S n gr gs 8 100 1029 2112 CB 1033 2012 M 0 300 1 PP S n gr 0 lc 0 lj /fm 256 def gs 1175 700 612 1858 CB 299 99 1485 2114 B 1 F S n gr 1 lc 1 lj gs 8 100 1629 2112 CB 1633 2012 M 0 300 1 PP S n gr 0 lc 0 lj /fm 256 def 675 149 997 2289 B 1 F S n 1 lc 1 lj gs 9 150 1216 2287 CB 1220 2137 M 0 450 1 PP S n gr gs 9 150 1441 2287 CB 1445 2137 M 0 450 1 PP S n gr 32 0 0 58 58 0 0 0 55 /Palatino-Bold /font24 ANSIFont font 0 0 0 fC gs 1175 700 612 1858 CB 775 2125 87 (468) 87 SB gr gs 1175 700 612 1858 CB 925 2125 87 (575) 87 SB gr gs 1175 700 612 1858 CB 1075 2125 87 (677) 87 SB gr gs 1175 700 612 1858 CB 1037 2325 87 (410) 87 SB gr gs 1175 700 612 1858 CB 1262 2325 87 (468) 87 SB gr gs 1175 700 612 1858 CB 1525 2325 87 (575) 87 SB gr 0 lc 0 lj 255 255 255 fC /fm 256 def 149 74 1260 2114 B 1 F S n 0 0 0 fC gs 1175 700 612 1858 CB 1300 2125 87 (677) 87 SB gr gs 1175 700 612 1858 CB 1525 2125 87 (468) 87 SB gr gs 1175 700 612 1858 CB 1675 2125 87 (575) 87 SB gr 255 255 255 fC /fm 256 def 150 95 622 1868 B 1 F S n 0 0 0 fC /fm 256 def 920 2087 M 37 46 8 -9 13 -12 -58 -25 4 PP 1 F n 1 lc 1 lj 6 4 SP gs 105 88 770 1962 CB 666 1875 M 313 262 1 PP S n gr gs 1175 700 612 1858 CB 662 1875 87 (520) 87 SB gr 32 0 0 75 75 0 0 0 69 /Palatino-Bold /font24 ANSIFont font gs 1175 700 612 1858 CB 1145 2462 298 (Object Y) 298 SB gr 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 803 2608 794 (Figure 1: Object Y Is About To Roll Back) 794 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 2710 131 (Figure ) 133 SB 433 2710 32 (1 ) 34 SB 467 2710 129 (shows ) 131 SB 598 2710 32 (a ) 34 SB 632 2710 134 (TWOS ) 136 SB 768 2710 120 (object ) 122 SB 890 2710 117 (about ) 119 SB 1009 2710 48 (to ) 50 SB 1059 2710 169 (undergo ) 171 SB 1230 2710 32 (a ) 34 SB 1264 2710 172 (rollback. ) 174 SB 1438 2710 11 ( ) 13 SB 1451 2710 68 (An ) 70 SB 1521 2710 120 (object ) 122 SB 1643 2710 139 (named ) 141 SB 1784 2710 39 (Y ) 41 SB 1825 2710 74 (has ) 76 SB 1901 2710 199 (performed) 199 SB 300 2761 131 (events ) 132 SB 432 2761 65 (for ) 66 SB 498 2761 136 (virtual ) 137 SB 635 2761 112 (times ) 113 SB 748 2761 61 (up ) 62 SB 810 2761 48 (to ) 49 SB 859 2761 85 (677. ) 86 SB 945 2761 11 ( ) 12 SB 957 2761 49 (In ) 50 SB 1007 2761 79 (this ) 80 SB 1087 2761 179 (diagram, ) 180 SB 1267 2761 39 (Y ) 40 SB 1307 2761 157 (consists ) 158 SB 1465 2761 48 (of ) 50 SB 1515 2761 32 (a ) 34 SB 1549 2761 125 (queue ) 127 SB 1676 2761 48 (of ) 50 SB 1726 2761 111 (input ) 113 SB 1839 2761 186 (messages ) 188 SB 2027 2761 73 (that) 73 SB 300 2812 100 (have ) 104 SB 404 2812 98 (been ) 102 SB 506 2812 169 (received ) 173 SB 679 2812 82 (and ) 86 SB 765 2812 82 (will ) 86 SB 851 2812 114 (cause ) 118 SB 969 2812 131 (events ) 135 SB 1104 2812 48 (to ) 52 SB 1156 2812 54 (be ) 58 SB 1214 2812 88 (run; ) 92 SB 1306 2812 32 (a ) 36 SB 1342 2812 125 (queue ) 129 SB 1471 2812 48 (of ) 53 SB 1524 2812 137 (output ) 142 SB 1666 2812 186 (messages ) 191 SB 1857 2812 192 (produced ) 197 SB 2054 2812 46 (by) 46 SB 300 2863 131 (events ) 132 SB 432 2863 77 (run ) 78 SB 510 2863 57 (by ) 59 SB 569 2863 79 (this ) 81 SB 650 2863 131 (object; ) 133 SB 783 2863 32 (a ) 34 SB 817 2863 125 (queue ) 127 SB 944 2863 48 (of ) 50 SB 994 2863 116 (states ) 118 SB 1112 2863 192 (produced ) 194 SB 1306 2863 57 (by ) 59 SB 1365 2863 131 (events ) 133 SB 1498 2863 77 (run ) 79 SB 1577 2863 57 (by ) 59 SB 1636 2863 79 (this ) 81 SB 1717 2863 131 (object; ) 133 SB 1850 2863 82 (and ) 84 SB 1934 2863 32 (a ) 34 SB 1968 2863 132 (control) 132 SB 1 #C statusdict begin /manualfeed false store end EJ RS %%PageTrailer %%PageResources: font Palatino-Bold %%+ font Palatino-Italic %%+ font Palatino-Roman %%Page: 4 4 %%PageResources: (atend) SS 0 0 25 25 798 1100 300 SM 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 0 0 0 fC 300 225 111 (block ) 116 SB 416 225 153 (storing, ) 158 SB 574 225 139 (among ) 144 SB 718 225 109 (other ) 114 SB 832 225 137 (things, ) 142 SB 974 225 69 (the ) 74 SB 1048 225 94 (time ) 99 SB 1147 225 48 (of ) 53 SB 1200 225 69 (the ) 74 SB 1274 225 91 (next ) 96 SB 1370 225 113 (event ) 118 SB 1488 225 48 (to ) 53 SB 1541 225 54 (be ) 60 SB 1601 225 88 (run. ) 94 SB 1695 225 11 ( ) 17 SB 1712 225 130 (Object ) 136 SB 1848 225 39 (Y ) 45 SB 1893 225 41 (is ) 47 SB 1940 225 117 (about ) 123 SB 2063 225 37 (to) 37 SB 300 276 143 (receive ) 145 SB 445 276 32 (a ) 34 SB 479 276 90 (new ) 92 SB 571 276 179 (message, ) 181 SB 752 276 46 (at ) 48 SB 800 276 94 (time ) 96 SB 896 276 85 (520. ) 87 SB 983 276 11 ( ) 13 SB 996 276 76 (But ) 78 SB 1074 276 39 (Y ) 41 SB 1115 276 74 (has ) 76 SB 1191 276 151 (already ) 153 SB 1344 276 265 (optimistically ) 267 SB 1611 276 77 (run ) 79 SB 1690 276 56 (an ) 58 SB 1748 276 113 (event ) 115 SB 1863 276 65 (for ) 67 SB 1930 276 94 (time ) 96 SB 2026 276 74 (575,) 74 SB 300 327 125 (which ) 126 SB 426 327 139 (should ) 140 SB 566 327 100 (have ) 101 SB 667 327 98 (been ) 99 SB 766 327 77 (run ) 78 SB 844 327 97 (after ) 98 SB 942 327 69 (the ) 70 SB 1012 327 113 (event ) 114 SB 1126 327 46 (at ) 47 SB 1173 327 94 (time ) 95 SB 1268 327 85 (520. ) 86 SB 1354 327 11 ( ) 13 SB 1367 327 203 (Therefore, ) 205 SB 1572 327 134 (TWOS ) 136 SB 1708 327 105 (must ) 107 SB 1815 327 75 (roll ) 77 SB 1892 327 97 (back ) 99 SB 1991 327 109 (object) 109 SB 300 378 39 (Y ) 45 SB 345 378 48 (to ) 54 SB 399 378 140 (restore ) 146 SB 545 378 55 (its ) 61 SB 606 378 98 (state ) 104 SB 710 378 65 (for ) 71 SB 781 378 69 (the ) 75 SB 856 378 113 (event ) 119 SB 975 378 46 (at ) 52 SB 1027 378 94 (time ) 100 SB 1127 378 74 (520 ) 80 SB 1207 378 82 (and ) 88 SB 1295 378 109 (undo ) 115 SB 1410 378 79 (any ) 85 SB 1495 378 248 (computation ) 255 SB 1750 378 176 (resulting ) 183 SB 1933 378 102 (from ) 109 SB 2042 378 58 (the) 58 SB 300 429 211 (incorrectly ) 218 SB 518 429 262 (synchronized ) 269 SB 787 429 113 (event ) 120 SB 907 429 46 (at ) 53 SB 960 429 94 (time ) 101 SB 1061 429 85 (575. ) 92 SB 1153 429 11 ( ) 19 SB 1172 429 131 (Figure ) 139 SB 1311 429 32 (2 ) 40 SB 1351 429 129 (shows ) 137 SB 1488 429 69 (the ) 77 SB 1565 429 98 (local ) 106 SB 1671 429 117 (result ) 125 SB 1796 429 48 (of ) 56 SB 1852 429 79 (this ) 87 SB 1939 429 161 (rollback.) 161 SB 300 480 757 (Note, however, that Y sent a message to ) 758 SB 1058 480 109 (some ) 110 SB 1168 480 109 (other ) 110 SB 1278 480 120 (object ) 121 SB 1399 480 46 (at ) 47 SB 1446 480 94 (time ) 95 SB 1541 480 85 (575, ) 86 SB 1627 480 125 (which ) 126 SB 1753 480 116 (could ) 117 SB 1870 480 100 (have ) 101 SB 1971 480 129 (caused) 129 SB 300 531 252 (that object to ) 253 SB 553 531 77 (run ) 78 SB 631 531 142 (further ) 143 SB 774 531 131 (events ) 132 SB 906 531 82 (and ) 83 SB 989 531 99 (send ) 100 SB 1089 531 108 (more ) 109 SB 1198 531 197 (messages. ) 198 SB 1396 531 11 ( ) 12 SB 1408 531 156 (Though ) 157 SB 1565 531 72 (not ) 73 SB 1638 531 192 (described ) 193 SB 1831 531 103 (here, ) 104 SB 1935 531 134 (TWOS ) 135 SB 2070 531 30 (is) 30 SB 300 582 1088 (able to correctly roll back and cancel any of the secondary ) 1089 SB 1389 582 130 (effects ) 131 SB 1520 582 48 (of ) 49 SB 1569 582 56 (an ) 57 SB 1626 582 222 (improperly ) 223 SB 1849 582 251 (synchronized) 251 SB 300 633 805 (event. See [Jefferson 87] for further details.) 805 SB 1 lc 1 lj 0 0 0 pC 6 4 SP 255 255 255 fC /fm 256 def 1279 744 1578 989 56 56 RR 1 F S n 0 lc 0 lj /fm 256 def 600 99 678 815 B 1 F S n 1 lc 1 lj gs 9 100 972 813 CB 976 713 M 0 300 1 PP S n gr gs 9 100 1122 813 CB 1127 713 M 0 300 1 PP S n gr 0 lc 0 lj /fm 256 def gs 1063 525 668 734 CB 149 99 1579 815 B 1 F S n gr /fm 256 def 449 149 1204 990 B 1 F S n 1 lc 1 lj gs 8 150 1423 988 CB 1427 838 M 0 450 1 PP S n gr 32 0 0 58 58 0 0 0 55 /Palatino-Bold /font24 ANSIFont font 0 0 0 fC gs 1063 525 668 734 CB 718 826 87 (468) 87 SB gr gs 1063 525 668 734 CB 1018 826 87 (575) 87 SB gr gs 1063 525 668 734 CB 1168 826 87 (677) 87 SB gr gs 1063 525 668 734 CB 1243 1026 87 (410) 87 SB gr gs 1063 525 668 734 CB 1468 1026 87 (468) 87 SB gr 0 lc 0 lj 255 255 255 fC /fm 256 def 149 74 1354 815 B 1 F S n 0 0 0 fC gs 1063 525 668 734 CB 1389 826 87 (520) 87 SB gr gs 1063 525 668 734 CB 1618 826 87 (468) 87 SB gr 32 0 0 75 75 0 0 0 69 /Palatino-Bold /font24 ANSIFont font gs 1063 525 668 734 CB 1239 1167 298 (Object Y) 298 SB gr 1 lc 1 lj gs 9 100 822 813 CB 826 713 M 0 300 1 PP S n gr 32 0 0 58 58 0 0 0 55 /Palatino-Bold /font24 ANSIFont font gs 1063 525 668 734 CB 864 826 87 (520) 87 SB gr 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 838 1309 723 (Figure 2: Object Y After the Rollback) 723 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 1411 58 (At ) 66 SB 366 1411 79 (any ) 87 SB 453 1411 114 (given ) 122 SB 575 1411 166 (moment ) 174 SB 749 1411 47 (in ) 55 SB 804 1411 32 (a ) 40 SB 844 1411 134 (TWOS ) 142 SB 986 1411 88 (run, ) 97 SB 1083 1411 69 (the ) 78 SB 1161 1411 239 (simulation\222s ) 248 SB 1409 1411 138 (objects ) 147 SB 1556 1411 100 (have ) 109 SB 1665 1411 210 (performed ) 219 SB 1884 1411 109 (some ) 118 SB 2002 1411 98 (work) 98 SB 300 1462 186 (correctly, ) 190 SB 490 1462 82 (and ) 86 SB 576 1462 109 (some ) 113 SB 689 1462 109 (work ) 113 SB 802 1462 47 (in ) 51 SB 853 1462 116 (error. ) 120 SB 973 1462 11 ( ) 16 SB 989 1462 134 (TWOS ) 139 SB 1128 1462 233 (periodically ) 238 SB 1366 1462 192 (calculates ) 197 SB 1563 1462 69 (the ) 74 SB 1637 1462 145 (earliest ) 150 SB 1787 1462 136 (virtual ) 141 SB 1928 1462 94 (time ) 99 SB 2027 1462 73 (that) 73 SB 300 1513 116 (could ) 122 SB 422 1513 79 (still ) 85 SB 507 1513 54 (be ) 60 SB 567 1513 47 (in ) 53 SB 620 1513 116 (error. ) 122 SB 742 1513 11 ( ) 17 SB 759 1513 91 (Any ) 97 SB 856 1513 109 (work ) 115 SB 971 1513 104 (done ) 110 SB 1081 1513 65 (for ) 72 SB 1153 1513 136 (virtual ) 143 SB 1296 1513 112 (times ) 119 SB 1415 1513 130 (earlier ) 137 SB 1552 1513 94 (than ) 101 SB 1653 1513 84 (that ) 91 SB 1744 1513 94 (time ) 101 SB 1845 1513 82 (will ) 89 SB 1934 1513 116 (never ) 123 SB 2057 1513 43 (be) 43 SB 300 1565 121 (rolled ) 125 SB 425 1565 108 (back, ) 112 SB 537 1565 82 (and ) 86 SB 623 1565 75 (can ) 79 SB 702 1565 54 (be ) 58 SB 32 0 0 42 42 0 0 0 40 /Palatino-Italic /font26 ANSIFont font 760 1564 179 (committed) 179 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 939 1565 22 (. ) 26 SB 965 1565 11 ( ) 15 SB 980 1565 98 (Both ) 102 SB 1082 1565 131 (events ) 135 SB 1217 1565 82 (and ) 86 SB 1303 1565 186 (messages ) 190 SB 1493 1565 75 (can ) 79 SB 1572 1565 54 (be ) 58 SB 1630 1565 224 (committed. ) 228 SB 1858 1565 11 ( ) 15 SB 1873 1565 44 (A ) 48 SB 32 0 0 42 42 0 0 0 40 /Palatino-Italic /font26 ANSIFont font 1921 1564 179 (committed) 179 SB 300 1616 137 (message) 137 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 437 1617 11 ( ) 13 SB 450 1617 41 (is ) 43 SB 493 1617 78 (one ) 80 SB 573 1617 84 (that ) 86 SB 659 1617 132 (would ) 134 SB 793 1617 100 (have ) 102 SB 895 1617 98 (been ) 100 SB 995 1617 87 (sent ) 89 SB 1084 1617 47 (in ) 50 SB 1134 1617 69 (the ) 72 SB 1206 1617 201 (sequential ) 204 SB 1410 1617 77 (run ) 80 SB 1490 1617 48 (of ) 51 SB 1541 1617 69 (the ) 72 SB 1613 1617 185 (program, ) 188 SB 1801 1617 82 (and ) 85 SB 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(of ) 58 SB 358 2178 97 (such ) 107 SB 465 2178 161 (devices. ) 171 SB 636 2178 11 ( ) 21 SB 657 2178 100 (Data ) 110 SB 767 2178 147 (written ) 157 SB 924 2178 48 (to ) 58 SB 982 2178 150 (devices ) 161 SB 1143 2178 72 (not ) 83 SB 1226 2178 123 (under ) 134 SB 1360 2178 134 (TWOS ) 145 SB 1505 2178 143 (control ) 154 SB 1659 2178 136 (cannot ) 147 SB 1806 2178 54 (be ) 65 SB 1871 2178 121 (rolled ) 132 SB 2003 2178 97 (back.) 97 SB 300 2229 203 (Therefore, ) 206 SB 506 2229 114 (when ) 117 SB 623 2229 32 (a ) 35 SB 658 2229 91 (user ) 94 SB 752 2229 167 (requests ) 170 SB 922 2229 97 (such ) 100 SB 1022 2229 32 (a ) 35 SB 1057 2229 120 (write, ) 123 SB 1180 2229 134 (TWOS ) 137 SB 1317 2229 105 (must ) 108 SB 1425 2229 113 (delay ) 116 SB 1541 2229 69 (the ) 72 SB 1613 2229 123 (actual ) 127 SB 1740 2229 83 (I/O ) 87 SB 1827 2229 98 (until ) 102 SB 1929 2229 69 (the ) 73 SB 2002 2229 98 (write) 98 SB 300 2280 149 (request ) 151 SB 451 2280 41 (is ) 43 SB 494 2280 138 (certain ) 140 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(their ) 99 SB 852 2382 153 (commit ) 154 SB 1006 2382 109 (point ) 110 SB 1116 2382 41 (is ) 42 SB 1158 2382 169 (reached. ) 170 SB 1328 2382 11 ( ) 12 SB 1340 2382 147 (Output ) 148 SB 1488 2382 47 (in ) 48 SB 1536 2382 134 (TWOS ) 135 SB 1671 2382 92 (uses ) 93 SB 1764 2382 69 (the ) 70 SB 1834 2382 107 (same ) 109 SB 1943 2382 157 (message) 157 SB 300 2433 223 (mechanism ) 230 SB 530 2433 50 (as ) 57 SB 587 2433 113 (event ) 120 SB 707 2433 225 (scheduling, ) 232 SB 939 2433 52 (so ) 59 SB 998 2433 232 (cancellation ) 239 SB 1237 2433 48 (of ) 55 SB 1292 2433 121 (rolled ) 128 SB 1420 2433 97 (back ) 104 SB 1524 2433 137 (output ) 144 SB 1668 2433 41 (is ) 49 SB 1717 2433 318 (straightforward. ) 326 SB 2043 2433 11 ( ) 19 SB 2062 2433 38 (In) 38 SB 300 2484 293 (general, TWOS ) 294 SB 594 2484 105 (must ) 106 SB 700 2484 113 (delay ) 114 SB 814 2484 223 (performing ) 224 SB 1038 2484 79 (any ) 80 SB 1118 2484 124 (action ) 125 SB 1243 2484 37 (it ) 38 SB 1281 2484 136 (cannot ) 137 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173 (allowing ) 178 SB 1795 632 305 (experimentation) 305 SB 300 683 901 (with a number of different internal mechanisms.) 901 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 784 927 (3. 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/Palatino-Roman /font27 ANSIFont font 300 2361 1469 (Correctness problems with TWOS arose from several sources. These included:) 1469 SB 450 2462 25 (\225) 25 SB 475 2462 361 ( Improper rollback) 361 SB 450 2563 25 (\225) 25 SB 475 2563 848 ( Failure to make progress in the computation) 848 SB 450 2664 25 (\225) 25 SB 475 2664 553 ( Non-deterministic execution) 553 SB 450 2765 25 (\225) 25 SB 475 2765 448 ( Improper commitment) 448 SB 300 2866 895 (Each of these areas will be examined separately.) 895 SB 1 #C statusdict begin /manualfeed false store end EJ RS %%PageTrailer %%PageResources: font Palatino-Bold %%+ font Palatino-Roman %%Page: 6 6 %%PageResources: (atend) SS 0 0 25 25 798 1100 300 SM 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 0 0 0 fC 300 225 472 (3.1.1 Improper Rollback) 472 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 327 81 (The ) 84 SB 384 327 163 (primary ) 166 SB 550 327 133 (source ) 136 SB 686 327 48 (of ) 51 SB 737 327 454 (synchronization-related ) 457 SB 1194 327 220 (correctness ) 223 SB 1417 327 123 (errors ) 126 SB 1543 327 47 (in ) 50 SB 1593 327 69 (the ) 72 SB 1665 327 256 (development ) 260 SB 1925 327 48 (of ) 52 SB 1977 327 123 (TWOS) 123 SB 300 378 85 (was ) 86 SB 386 378 187 (improper ) 188 SB 574 378 172 (rollback. ) 173 SB 747 378 11 ( ) 12 SB 759 378 121 (When ) 122 SB 881 378 69 (the ) 70 SB 951 378 141 (system ) 142 SB 1093 378 142 (detects ) 143 SB 1236 378 32 (a ) 34 SB 1270 378 310 (synchronization ) 312 SB 1582 378 116 (error, ) 118 SB 1700 378 69 (the ) 71 SB 1771 378 109 (work ) 111 SB 1882 378 104 (done ) 106 SB 1988 378 73 (out ) 75 SB 2063 378 37 (of) 37 SB 300 429 114 (order ) 120 SB 420 429 105 (must ) 111 SB 531 429 54 (be ) 60 SB 591 429 121 (rolled ) 127 SB 718 429 97 (back ) 103 SB 821 429 82 (and ) 88 SB 909 429 69 (the ) 75 SB 984 429 159 (affected ) 165 SB 1149 429 88 (part ) 94 SB 1243 429 48 (of ) 54 SB 1297 429 69 (the ) 75 SB 1372 429 141 (system ) 147 SB 1519 429 166 (restored ) 173 SB 1692 429 48 (to ) 55 SB 1747 429 69 (the ) 76 SB 1823 429 98 (state ) 105 SB 1928 429 37 (it ) 44 SB 1972 429 85 (was ) 92 SB 2064 429 36 (in) 36 SB 300 480 128 (before ) 132 SB 432 480 69 (the ) 73 SB 505 480 310 (synchronization ) 314 SB 819 480 105 (error ) 109 SB 928 480 188 (occurred. ) 192 SB 1120 480 11 ( ) 15 SB 1135 480 270 (Conceptually, ) 274 SB 1409 480 79 (this ) 83 SB 1492 480 155 (amount ) 159 SB 1651 480 48 (to ) 52 SB 1703 480 179 (restoring ) 183 SB 1886 480 69 (the ) 74 SB 1960 480 98 (state ) 103 SB 2063 480 37 (of) 37 SB 300 531 69 (the ) 71 SB 371 531 120 (object ) 122 SB 493 531 84 (that ) 86 SB 579 531 73 (ran ) 75 SB 654 531 56 (an ) 58 SB 712 531 113 (event ) 115 SB 827 531 73 (out ) 75 SB 902 531 48 (of ) 50 SB 952 531 114 (order ) 116 SB 1068 531 82 (and ) 84 SB 1152 531 197 (cancelling ) 199 SB 1351 531 79 (any ) 81 SB 1432 531 87 (side ) 90 SB 1522 531 130 (effects ) 133 SB 1655 531 84 (that ) 87 SB 1742 531 55 (its ) 58 SB 1800 531 113 (event ) 116 SB 1916 531 92 (may ) 95 SB 2011 531 89 (have) 89 SB 300 582 140 (caused.) 140 SB 300 683 190 (Restoring ) 193 SB 493 683 69 (the ) 72 SB 565 683 98 (state ) 101 SB 666 683 41 (is ) 44 SB 710 683 248 (conceptually ) 251 SB 961 683 146 (simple. ) 149 SB 1110 683 11 ( ) 14 SB 1124 683 60 (By ) 63 SB 1187 683 158 (keeping ) 161 SB 1348 683 168 (multiple ) 171 SB 1519 683 128 (copies ) 131 SB 1650 683 48 (of ) 52 SB 1702 683 69 (the ) 73 SB 1775 683 150 (object\222s ) 154 SB 1929 683 109 (state, ) 113 SB 2042 683 58 (the) 58 SB 300 734 1388 (system need only find the proper copy of the state and replace the current ) 1389 SB 1689 734 101 (copy ) 102 SB 1791 734 96 (with ) 97 SB 1888 734 84 (that ) 85 SB 1973 734 127 (proper) 127 SB 300 785 112 (copy. ) 113 SB 413 785 11 ( ) 12 SB 425 785 39 (If ) 40 SB 465 785 74 (full ) 75 SB 540 785 128 (copies ) 129 SB 669 785 48 (of ) 49 SB 718 785 116 (states ) 117 SB 835 785 69 (are ) 70 SB 905 785 104 (kept, ) 105 SB 1010 785 69 (the ) 70 SB 1080 785 151 (process ) 152 SB 1232 785 41 (is ) 42 SB 1274 785 95 (very ) 96 SB 1370 785 146 (simple. ) 147 SB 1517 785 11 ( ) 12 SB 1529 785 39 (If ) 40 SB 1569 785 93 (only ) 94 SB 1663 785 160 (changes ) 161 SB 1824 785 47 (in ) 48 SB 1872 785 69 (the ) 70 SB 1942 785 98 (state ) 100 SB 2042 785 58 (are) 58 SB 300 836 104 (kept, ) 123 SB 423 836 93 (then ) 112 SB 535 836 69 (the ) 88 SB 623 836 214 (restoration ) 233 SB 856 836 48 (of ) 67 SB 923 836 32 (a ) 52 SB 975 836 138 (proper ) 158 SB 1133 836 98 (state ) 118 SB 1251 836 41 (is ) 61 SB 1312 836 149 (slightly ) 169 SB 1481 836 108 (more ) 128 SB 1609 836 180 (complex, ) 200 SB 1809 836 73 (but ) 93 SB 1902 836 79 (still ) 99 SB 2001 836 99 (fairly) 99 SB 300 887 318 (straightforward, ) 326 SB 626 887 47 (in ) 55 SB 681 887 188 (principle. ) 196 SB 877 887 11 ( ) 19 SB 896 887 171 (Changes ) 179 SB 1075 887 69 (are ) 78 SB 1153 887 164 (undone, ) 173 SB 1326 887 154 (starting ) 163 SB 1489 887 102 (from ) 111 SB 1600 887 69 (the ) 78 SB 1678 887 103 (most ) 112 SB 1790 887 136 (recent, ) 145 SB 1935 887 98 (until ) 107 SB 2042 887 58 (the) 58 SB 300 938 443 (proper state is restored.) 443 SB 300 1039 91 (Side ) 92 SB 392 1039 130 (effects ) 131 SB 523 1039 69 (are ) 70 SB 593 1039 116 (much ) 117 SB 710 1039 145 (trickier ) 146 SB 856 1039 48 (to ) 49 SB 905 1039 120 (undo, ) 121 SB 1026 1039 193 (especially ) 195 SB 1221 1039 37 (if ) 39 SB 1260 1039 110 (those ) 112 SB 1372 1039 87 (side ) 89 SB 1461 1039 130 (effects ) 132 SB 1593 1039 75 (can ) 77 SB 1670 1039 114 (cause ) 116 SB 1786 1039 142 (further ) 144 SB 1930 1039 131 (events ) 133 SB 2063 1039 37 (to) 37 SB 300 1090 54 (be ) 56 SB 356 1090 77 (run ) 80 SB 436 1090 46 (at ) 49 SB 485 1090 109 (other ) 112 SB 597 1090 149 (objects. ) 152 SB 749 1090 11 ( ) 14 SB 763 1090 176 (Tracking ) 179 SB 942 1090 119 (down ) 122 SB 1064 1090 115 (every ) 118 SB 1182 1090 162 (possible ) 165 SB 1347 1090 87 (side ) 90 SB 1437 1090 112 (effect ) 115 SB 1552 1090 48 (of ) 51 SB 1603 1090 32 (a ) 35 SB 1638 1090 248 (computation ) 251 SB 1889 1090 92 (may ) 95 SB 1984 1090 116 (sound) 116 SB 300 1141 95 (very ) 97 SB 397 1141 250 (complicated, ) 252 SB 649 1141 82 (and ) 84 SB 733 1141 37 (it ) 39 SB 772 1141 75 (can ) 77 SB 849 1141 65 (be, ) 67 SB 916 1141 128 (unless ) 130 SB 1046 1141 88 (care ) 90 SB 1136 1141 41 (is ) 43 SB 1179 1141 100 (used ) 102 SB 1281 1141 47 (in ) 49 SB 1330 1141 166 (defining ) 168 SB 1498 1141 105 (what ) 107 SB 1605 1141 87 (side ) 90 SB 1695 1141 130 (effects ) 133 SB 1828 1141 32 (a ) 35 SB 1863 1141 237 (computation) 237 SB 300 1192 75 (can ) 78 SB 378 1192 111 (have. ) 114 SB 492 1192 11 ( ) 14 SB 506 1192 134 (TWOS ) 137 SB 643 1192 174 (carefully ) 177 SB 820 1192 153 (ensures ) 156 SB 976 1192 84 (that ) 87 SB 1063 1192 69 (the ) 72 SB 1135 1192 93 (only ) 96 SB 1231 1192 162 (possible ) 165 SB 1396 1192 87 (side ) 91 SB 1487 1192 112 (effect ) 116 SB 1603 1192 102 (from ) 106 SB 1709 1192 32 (a ) 36 SB 1745 1192 248 (computation ) 252 SB 1997 1192 41 (is ) 45 SB 2042 1192 58 (the) 58 SB 300 1243 158 (sending ) 160 SB 460 1243 48 (of ) 50 SB 510 1243 78 (one ) 80 SB 590 1243 51 (or ) 53 SB 643 1243 108 (more ) 110 SB 753 1243 197 (messages. ) 199 SB 952 1243 11 ( ) 13 SB 965 1243 91 (Any ) 93 SB 1058 1243 112 (effect ) 114 SB 1172 1243 84 (that ) 86 SB 1258 1243 69 (the ) 71 SB 1329 1243 91 (user ) 93 SB 1422 1243 146 (wished ) 148 SB 1570 1243 48 (to ) 50 SB 1620 1243 177 (produce, ) 180 SB 1800 1243 54 (be ) 57 SB 1857 1243 37 (it ) 40 SB 1897 1243 203 (scheduling) 203 SB 300 1294 154 (another ) 161 SB 461 1294 113 (event ) 120 SB 581 1294 51 (or ) 58 SB 639 1294 223 (performing ) 230 SB 869 1294 137 (output ) 144 SB 1013 1294 48 (to ) 55 SB 1068 1294 56 (an ) 63 SB 1131 1294 83 (I/O ) 90 SB 1221 1294 143 (device, ) 150 SB 1371 1294 41 (is ) 48 SB 1419 1294 83 (cast ) 90 SB 1509 1294 47 (in ) 54 SB 1563 1294 69 (the ) 76 SB 1639 1294 102 (form ) 110 SB 1749 1294 48 (of ) 56 SB 1805 1294 32 (a ) 40 SB 1845 1294 179 (message. ) 187 SB 2032 1294 11 ( ) 19 SB 2051 1294 49 (By) 49 SB 300 1345 1624 (limiting the problem to a single class of side effects, undoing them proved much easier.) 1624 SB 300 1446 134 (TWOS ) 139 SB 439 1446 147 (undoes ) 152 SB 591 1446 55 (its ) 60 SB 651 1446 93 (only ) 98 SB 749 1446 196 (permitted ) 201 SB 950 1446 102 (form ) 107 SB 1057 1446 48 (of ) 53 SB 1110 1446 87 (side ) 92 SB 1202 1446 112 (effect ) 117 SB 1319 1446 57 (by ) 62 SB 1381 1446 168 (message ) 173 SB 1554 1446 243 (cancellation. ) 248 SB 1802 1446 11 ( ) 16 SB 1818 1446 134 (TWOS ) 139 SB 1957 1446 117 (keeps ) 122 SB 2079 1446 21 (a) 21 SB 300 1497 101 (copy ) 103 SB 403 1497 48 (of ) 50 SB 453 1497 79 (any ) 81 SB 534 1497 168 (message ) 170 SB 704 1497 87 (sent ) 89 SB 793 1497 57 (by ) 59 SB 852 1497 56 (an ) 58 SB 910 1497 131 (object. ) 133 SB 1043 1497 11 ( ) 13 SB 1056 1497 39 (If ) 41 SB 1097 1497 69 (the ) 71 SB 1168 1497 113 (event ) 115 SB 1283 1497 84 (that ) 86 SB 1369 1497 87 (sent ) 89 SB 1458 1497 32 (a ) 34 SB 1492 1497 168 (message ) 170 SB 1662 1497 41 (is ) 43 SB 1705 1497 121 (rolled ) 123 SB 1828 1497 108 (back, ) 110 SB 1938 1497 69 (the ) 72 SB 2010 1497 90 (copy) 90 SB 300 1548 48 (of ) 58 SB 358 1548 69 (the ) 79 SB 437 1548 168 (message ) 178 SB 615 1548 128 (serves ) 138 SB 753 1548 50 (as ) 60 SB 813 1548 32 (a ) 42 SB 855 1548 133 (record ) 143 SB 998 1548 84 (that ) 94 SB 1092 1548 69 (the ) 79 SB 1171 1548 168 (message ) 178 SB 1349 1548 85 (was ) 95 SB 1444 1548 98 (sent, ) 108 SB 1552 1548 82 (and ) 92 SB 1644 1548 139 (signals ) 149 SB 1793 1548 69 (the ) 80 SB 1873 1548 179 (necessity ) 190 SB 2063 1548 37 (of) 37 SB 300 1599 197 (cancelling ) 201 SB 501 1599 84 (that ) 88 SB 589 1599 179 (message. ) 183 SB 772 1599 11 ( ) 15 SB 787 1599 74 (For ) 78 SB 865 1599 220 (correctness ) 224 SB 1089 1599 193 (purposes, ) 197 SB 1286 1599 69 (the ) 73 SB 1359 1599 118 (entire ) 123 SB 1482 1599 168 (message ) 173 SB 1655 1599 101 (need ) 106 SB 1761 1599 72 (not ) 77 SB 1838 1599 54 (be ) 59 SB 1897 1599 131 (saved, ) 136 SB 2033 1599 67 (just) 67 SB 300 1650 1591 (sufficient information to permit its cancellation. \(Such information would include its ) 1592 SB 1892 1650 208 (destination) 208 SB 300 1701 82 (and ) 83 SB 383 1701 109 (some ) 110 SB 493 1701 102 (form ) 103 SB 596 1701 48 (of ) 50 SB 646 1701 141 (unique ) 143 SB 789 1701 207 (identifier.\) ) 209 SB 998 1701 11 ( ) 13 SB 1011 1701 134 (TWOS ) 136 SB 1147 1701 117 (keeps ) 119 SB 1266 1701 69 (the ) 71 SB 1337 1701 74 (full ) 76 SB 1413 1701 186 (messages ) 188 SB 1601 1701 65 (for ) 67 SB 1668 1701 248 (performance ) 250 SB 1918 1701 182 (purposes,) 182 SB 300 1752 663 (as will be discussed in section 3.2.3.) 663 SB 300 1853 39 (If ) 51 SB 351 1853 56 (an ) 68 SB 419 1853 197 (optimistic ) 209 SB 628 1853 190 (execution ) 203 SB 831 1853 141 (system ) 154 SB 985 1853 154 (permits ) 167 SB 1152 1853 79 (any ) 92 SB 1244 1853 109 (other ) 122 SB 1366 1853 99 (class ) 112 SB 1478 1853 48 (of ) 61 SB 1539 1853 87 (side ) 100 SB 1639 1853 141 (effects, ) 154 SB 1793 1853 93 (then ) 106 SB 1899 1853 32 (a ) 45 SB 1944 1853 156 (separate) 156 SB 300 1904 223 (mechanism ) 225 SB 525 1904 65 (for ) 67 SB 592 1904 168 (undoing ) 171 SB 763 1904 106 (them ) 109 SB 872 1904 105 (must ) 108 SB 980 1904 54 (be ) 57 SB 1037 1904 215 (supported. ) 218 SB 1255 1904 11 ( ) 14 SB 1269 1904 81 (The ) 84 SB 1353 1904 134 (TWOS ) 137 SB 1490 1904 210 (experience ) 213 SB 1703 1904 170 (suggests ) 173 SB 1876 1904 84 (that ) 87 SB 1963 1904 113 (using ) 116 SB 2079 1904 21 (a) 21 SB 300 1955 120 (single ) 124 SB 424 1955 87 (side ) 91 SB 515 1955 112 (effect ) 116 SB 631 1955 223 (mechanism ) 227 SB 858 1955 41 (is ) 45 SB 903 1955 116 (much ) 120 SB 1023 1955 163 (simpler. ) 167 SB 1190 1955 11 ( ) 16 SB 1206 1955 91 (Any ) 96 SB 1302 1955 87 (side ) 92 SB 1394 1955 112 (effect ) 117 SB 1511 1955 84 (that ) 89 SB 1600 1955 69 (the ) 74 SB 1674 1955 91 (user ) 96 SB 1770 1955 119 (needs ) 124 SB 1894 1955 48 (to ) 53 SB 1947 1955 153 (perform) 153 SB 300 2006 75 (can ) 78 SB 378 2006 54 (be ) 57 SB 435 2006 104 (done ) 107 SB 542 2006 57 (by ) 60 SB 602 2006 158 (sending ) 161 SB 763 2006 32 (a ) 35 SB 798 2006 168 (message ) 171 SB 969 2006 48 (to ) 51 SB 1020 2006 32 (a ) 35 SB 1055 2006 138 (special ) 141 SB 1196 2006 120 (object ) 123 SB 1319 2006 152 (capable ) 155 SB 1474 2006 48 (of ) 51 SB 1525 2006 223 (performing ) 226 SB 1751 2006 84 (that ) 88 SB 1839 2006 87 (side ) 91 SB 1930 2006 123 (effect. ) 127 SB 2057 2006 11 ( ) 15 SB 2072 2006 28 (If) 28 SB 300 2057 168 (message ) 171 SB 471 2057 243 (cancellation, ) 246 SB 717 2057 172 (rollback, ) 176 SB 893 2057 82 (and ) 86 SB 979 2057 248 (commitment ) 252 SB 1231 2057 69 (are ) 73 SB 1304 2057 173 (properly ) 177 SB 1481 2057 269 (implemented, ) 273 SB 1754 2057 232 (cancellation ) 236 SB 1990 2057 48 (of ) 52 SB 2042 2057 58 (the) 58 SB 300 2108 598 (side effect then becomes simple.) 598 SB 300 2209 88 (One ) 97 SB 397 2209 145 (natural ) 154 SB 551 2209 247 (consequence ) 256 SB 807 2209 48 (of ) 57 SB 864 2209 79 (this ) 88 SB 952 2209 192 (limitation ) 201 SB 1153 2209 41 (is ) 51 SB 1204 2209 84 (that ) 94 SB 1298 2209 141 (system ) 151 SB 1449 2209 189 (designers ) 199 SB 1648 2209 136 (cannot ) 146 SB 1794 2209 83 (rely ) 93 SB 1887 2209 58 (on ) 68 SB 1955 2209 145 (existing) 145 SB 300 2260 163 (libraries ) 170 SB 470 2260 51 (or ) 58 SB 528 2260 123 (utility ) 130 SB 658 2260 192 (programs ) 199 SB 857 2260 48 (to ) 55 SB 912 2260 158 (provide ) 165 SB 1077 2260 158 (support ) 165 SB 1242 2260 48 (to ) 55 SB 1297 2260 120 (users. ) 127 SB 1424 2260 11 ( ) 18 SB 1442 2260 62 (As ) 69 SB 1511 2260 56 (an ) 64 SB 1575 2260 179 (example, ) 187 SB 1762 2260 173 (dynamic ) 181 SB 1943 2260 157 (memory) 157 SB 300 2311 192 (allocation ) 195 SB 495 2311 47 (in ) 50 SB 545 2311 134 (TWOS ) 137 SB 682 2311 116 (could ) 119 SB 801 2311 72 (not ) 75 SB 876 2311 54 (be ) 57 SB 933 2311 184 (provided ) 187 SB 1120 2311 113 (using ) 116 SB 1236 2311 69 (the ) 72 SB 1308 2311 121 (UNIX ) 124 SB 32 0 0 42 42 0 0 0 33 /Courier /font0 ANSIFont font 1432 2317 200 (malloc\(\)) 200 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 1632 2311 11 ( ) 14 SB 1646 2311 86 (call, ) 90 SB 1736 2311 99 (even ) 103 SB 1839 2311 47 (in ) 51 SB 1890 2311 110 (those ) 114 SB 2004 2311 96 (cases) 96 SB 300 2362 127 (where ) 129 SB 429 2362 134 (TWOS ) 136 SB 565 2362 73 (ran ) 75 SB 640 2362 58 (on ) 60 SB 700 2362 73 (top ) 75 SB 775 2362 48 (of ) 50 SB 825 2362 32 (a ) 34 SB 859 2362 121 (UNIX ) 123 SB 982 2362 190 (operating ) 193 SB 1175 2362 152 (system. ) 155 SB 1330 2362 11 ( ) 14 SB 1344 2362 44 (A ) 47 SB 32 0 0 42 42 0 0 0 33 /Courier /font0 ANSIFont font 1391 2368 200 (malloc\(\)) 200 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 1591 2362 11 ( ) 14 SB 1605 2362 75 (call ) 78 SB 1683 2362 136 (cannot ) 139 SB 1822 2362 54 (be ) 57 SB 1879 2362 121 (rolled ) 124 SB 2003 2362 97 (back,) 97 SB 300 2413 50 (as ) 53 SB 353 2413 37 (it ) 40 SB 393 2413 41 (is ) 44 SB 437 2413 149 (outside ) 152 SB 589 2413 69 (the ) 72 SB 661 2413 116 (scope ) 119 SB 780 2413 48 (of ) 51 SB 831 2413 69 (the ) 72 SB 903 2413 197 (optimistic ) 201 SB 1104 2413 190 (execution ) 194 SB 1298 2413 152 (system. ) 156 SB 1454 2413 11 ( ) 15 SB 1469 2413 39 (It ) 43 SB 1512 2413 116 (could ) 120 SB 1632 2413 54 (be ) 58 SB 1690 2413 203 (effectively ) 207 SB 1897 2413 153 (undone ) 157 SB 2054 2413 46 (by) 46 SB 300 2464 238 (deallocating ) 241 SB 541 2464 69 (the ) 72 SB 613 2464 114 (space ) 117 SB 730 2464 206 (requested, ) 209 SB 939 2464 73 (but ) 76 SB 1015 2464 93 (then ) 96 SB 1111 2464 69 (the ) 72 SB 1183 2464 197 (optimistic ) 200 SB 1383 2464 190 (execution ) 193 SB 1576 2464 141 (system ) 144 SB 1720 2464 132 (would ) 135 SB 1855 2464 101 (need ) 105 SB 1960 2464 48 (to ) 52 SB 2012 2464 88 (keep) 88 SB 300 2515 105 (track ) 118 SB 418 2515 48 (of ) 61 SB 479 2515 56 (all ) 69 SB 32 0 0 42 42 0 0 0 33 /Courier /font0 ANSIFont font 548 2521 200 (malloc\(\)) 200 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 748 2515 41 (\222s ) 54 SB 802 2515 84 (that ) 97 SB 899 2515 103 (were ) 117 SB 1016 2515 126 (made. ) 140 SB 1156 2515 11 ( ) 25 SB 1181 2515 14 (\() 14 SB 32 0 0 42 42 0 0 0 33 /Courier /font0 ANSIFont font 1195 2521 200 (malloc\(\)) 200 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 1395 2515 11 ( ) 25 SB 1420 2515 74 (has ) 88 SB 1508 2515 56 (an ) 70 SB 1578 2515 202 (additional ) 216 SB 1794 2515 168 (problem ) 182 SB 1976 2515 65 (for ) 79 SB 2055 2515 45 (an) 45 SB 300 2566 197 (optimistic ) 218 SB 518 2566 190 (execution ) 211 SB 729 2566 152 (system, ) 173 SB 902 2566 47 (in ) 68 SB 970 2566 84 (that ) 105 SB 1075 2566 37 (it ) 58 SB 1133 2566 146 (returns ) 167 SB 1300 2566 32 (a ) 53 SB 1353 2566 146 (pointer ) 167 SB 1520 2566 48 (to ) 69 SB 1589 2566 123 (actual ) 144 SB 1733 2566 168 (memory ) 190 SB 1923 2566 177 (locations.) 177 SB 300 2617 248 (Dynamically ) 251 SB 551 2617 179 (allocated ) 182 SB 733 2617 168 (memory ) 171 SB 904 2617 41 (is ) 44 SB 948 2617 205 (essentially ) 208 SB 1156 2617 56 (an ) 59 SB 1215 2617 200 (expansion ) 203 SB 1418 2617 48 (of ) 51 SB 1469 2617 32 (a ) 36 SB 1505 2617 163 (process\222 ) 167 SB 1672 2617 109 (state, ) 113 SB 1785 2617 52 (so ) 56 SB 1841 2617 69 (the ) 73 SB 1914 2617 186 (optimistic) 186 SB 300 2668 141 (system ) 144 SB 444 2668 82 (will ) 85 SB 529 2668 101 (need ) 104 SB 633 2668 48 (to ) 51 SB 684 2668 99 (keep ) 102 SB 786 2668 168 (multiple ) 171 SB 957 2668 167 (versions ) 170 SB 1127 2668 48 (of ) 51 SB 1178 2668 241 (dynamically ) 244 SB 1422 2668 179 (allocated ) 182 SB 1604 2668 168 (memory ) 171 SB 1775 2668 196 (segments. ) 200 SB 1975 2668 11 ( ) 15 SB 1990 2668 110 (Using) 110 SB 32 0 0 42 42 0 0 0 33 /Courier /font0 ANSIFont font 300 2725 200 (malloc\(\)) 200 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 500 2719 11 ( ) 15 SB 515 2719 48 (to ) 53 SB 568 2719 68 (get ) 73 SB 641 2719 107 (these ) 112 SB 753 2719 185 (segments ) 190 SB 943 2719 231 (complicates ) 236 SB 1179 2719 158 (keeping ) 163 SB 1342 2719 105 (track ) 110 SB 1452 2719 48 (of ) 53 SB 1505 2719 168 (multiple ) 173 SB 1678 2719 167 (versions ) 172 SB 1850 2719 82 (and ) 87 SB 1937 2719 163 (ensuring) 163 SB 300 2770 943 (that the correct version is available upon rollback.\)) 943 SB 1 #C statusdict begin /manualfeed false store end EJ RS %%PageTrailer %%PageResources: font Courier %%+ font Palatino-Bold %%+ font Palatino-Roman %%Page: 7 7 %%PageResources: (atend) SS 0 0 25 25 798 1100 300 SM 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 0 0 0 fC 300 225 203 (Generally, ) 212 SB 512 225 104 (then, ) 113 SB 625 225 156 (existing ) 165 SB 790 225 150 (utilities ) 159 SB 949 225 136 (cannot ) 145 SB 1094 225 54 (be ) 63 SB 1157 225 100 (used ) 109 SB 1266 225 57 (by ) 66 SB 1332 225 197 (optimistic ) 206 SB 1538 225 190 (execution ) 199 SB 1737 225 159 (systems ) 168 SB 1905 225 128 (unless ) 137 SB 2042 225 58 (the) 58 SB 300 276 159 (systems ) 162 SB 462 276 189 (designers ) 192 SB 654 276 69 (are ) 72 SB 726 276 106 (quite ) 109 SB 835 276 91 (sure ) 94 SB 929 276 84 (that ) 87 SB 1016 276 110 (those ) 113 SB 1129 276 150 (utilities ) 153 SB 1282 276 90 (lead ) 93 SB 1375 276 48 (to ) 51 SB 1426 276 58 (no ) 61 SB 1487 276 87 (side ) 90 SB 1577 276 141 (effects, ) 144 SB 1721 276 51 (or ) 55 SB 1776 276 69 (the ) 73 SB 1849 276 189 (designers ) 193 SB 2042 276 58 (are) 58 SB 300 327 182 (prepared ) 187 SB 487 327 48 (to ) 53 SB 540 327 99 (keep ) 104 SB 644 327 105 (track ) 110 SB 754 327 48 (of ) 53 SB 807 327 93 (calls ) 98 SB 905 327 48 (to ) 53 SB 958 327 69 (the ) 74 SB 1032 327 150 (utilities ) 155 SB 1187 327 82 (and ) 87 SB 1274 327 109 (undo ) 114 SB 1388 327 79 (any ) 84 SB 1472 327 130 (effects ) 135 SB 1607 327 84 (that ) 89 SB 1696 327 92 (they ) 97 SB 1793 327 92 (may ) 97 SB 1890 327 111 (have. ) 116 SB 2006 327 11 ( ) 17 SB 2023 327 77 (One) 77 SB 300 378 109 (other ) 112 SB 412 378 132 (option ) 135 SB 547 378 41 (is ) 44 SB 591 378 48 (to ) 51 SB 642 378 230 (encapsulate ) 233 SB 875 378 69 (the ) 72 SB 947 378 123 (utility ) 127 SB 1074 378 47 (in ) 51 SB 1125 378 32 (a ) 36 SB 1161 378 167 (separate ) 171 SB 1332 378 120 (object ) 124 SB 1456 378 82 (and ) 86 SB 1542 378 137 (invoke ) 141 SB 1683 378 37 (it ) 41 SB 1724 378 68 (via ) 72 SB 1796 378 32 (a ) 36 SB 1832 378 179 (message. ) 183 SB 2015 378 11 ( ) 15 SB 2030 378 70 (The) 70 SB 300 429 123 (actual ) 125 SB 425 429 207 (invocation ) 209 SB 634 429 48 (of ) 50 SB 684 429 69 (the ) 71 SB 755 429 123 (utility ) 125 SB 880 429 41 (is ) 43 SB 923 429 159 (delayed ) 162 SB 1085 429 98 (until ) 101 SB 1186 429 69 (the ) 72 SB 1258 429 168 (message ) 171 SB 1429 429 41 (is ) 44 SB 1473 429 224 (committed, ) 227 SB 1700 429 152 (thereby ) 155 SB 1855 429 169 (assuring ) 172 SB 2027 429 73 (that) 73 SB 300 480 69 (the ) 72 SB 372 480 149 (request ) 152 SB 524 480 48 (to ) 51 SB 575 480 77 (run ) 80 SB 655 480 69 (the ) 72 SB 727 480 123 (utility ) 126 SB 853 480 82 (will ) 85 SB 938 480 72 (not ) 75 SB 1013 480 54 (be ) 57 SB 1070 480 121 (rolled ) 124 SB 1194 480 108 (back. ) 111 SB 1305 480 11 ( ) 14 SB 1319 480 91 (This ) 95 SB 1414 480 132 (option ) 136 SB 1550 480 82 (will ) 86 SB 1636 480 109 (work ) 113 SB 1749 480 101 (well, ) 105 SB 1854 480 184 (provided ) 188 SB 2042 480 58 (the) 58 SB 300 531 1529 (utility is not expected to return information to the caller. If the utility does return ) 1530 SB 1830 531 243 (information, ) 244 SB 2074 531 26 (it) 26 SB 300 582 82 (will ) 85 SB 385 582 72 (not ) 75 SB 460 582 60 (do ) 63 SB 523 582 52 (so ) 55 SB 578 582 98 (until ) 101 SB 679 582 69 (the ) 72 SB 751 582 153 (commit ) 156 SB 907 582 109 (point ) 112 SB 1019 582 74 (has ) 77 SB 1096 582 98 (been ) 101 SB 1197 582 169 (reached, ) 172 SB 1369 582 172 (delaying ) 175 SB 1544 582 138 (proper ) 141 SB 1685 582 190 (execution ) 193 SB 1878 582 46 (at ) 49 SB 1927 582 69 (the ) 72 SB 1999 582 101 (caller) 101 SB 300 633 1299 (until that time. The caller may perform other events, but they will be ) 1300 SB 1600 633 121 (rolled ) 122 SB 1722 633 97 (back ) 98 SB 1820 633 97 (once ) 98 SB 1918 633 69 (the ) 70 SB 1988 633 112 (utility) 112 SB 300 684 146 (returns ) 151 SB 451 684 55 (its ) 60 SB 511 684 243 (information. ) 248 SB 759 684 11 ( ) 16 SB 775 684 158 (Utilities ) 163 SB 938 684 187 (returning ) 192 SB 1130 684 131 (values ) 136 SB 1266 684 84 (that ) 89 SB 1355 684 11 ( ) 16 SB 1371 684 69 (are ) 74 SB 1445 684 48 (to ) 53 SB 1498 684 54 (be ) 59 SB 1557 684 100 (used ) 105 SB 1662 684 245 (immediately ) 250 SB 1912 684 139 (should ) 145 SB 2057 684 43 (be) 43 SB 300 735 147 (written ) 151 SB 451 735 57 (by ) 61 SB 512 735 69 (the ) 73 SB 585 735 141 (system ) 145 SB 730 735 200 (designers, ) 204 SB 934 735 52 (so ) 56 SB 990 735 84 (that ) 88 SB 1078 735 92 (they ) 97 SB 1175 735 75 (can ) 80 SB 1255 735 54 (be ) 59 SB 1314 735 140 (subject ) 145 SB 1459 735 48 (to ) 53 SB 1512 735 161 (rollback ) 166 SB 1678 735 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SB 1141 1295 186 (relatively ) 201 SB 1342 1295 104 (easy. ) 119 SB 1461 1295 11 ( ) 26 SB 1487 1295 119 (Many ) 134 SB 1621 1295 140 (known ) 155 SB 1776 1295 168 (message ) 183 SB 1959 1295 141 (passing) 141 SB 300 1346 241 (mechanisms ) 245 SB 545 1346 84 (that ) 88 SB 633 1346 196 (guarantee ) 200 SB 833 1346 165 (delivery ) 169 SB 1002 1346 75 (can ) 79 SB 1081 1346 54 (be ) 59 SB 1140 1346 111 (used. ) 116 SB 1256 1346 11 ( ) 16 SB 1272 1346 81 (The ) 86 SB 1358 1346 214 (scheduling ) 219 SB 1577 1346 259 (requirements ) 264 SB 1841 1346 156 (deserve ) 161 SB 2002 1346 98 (some) 98 SB 300 1397 406 (further consideration.) 406 SB 300 1498 81 (The ) 87 SB 387 1498 103 (most ) 109 SB 496 1498 137 (typical ) 143 SB 639 1498 214 (scheduling ) 220 SB 859 1498 125 (policy ) 131 SB 990 1498 100 (used ) 106 SB 1096 1498 47 (in ) 53 SB 1149 1498 136 (virtual ) 142 SB 1291 1498 94 (time ) 100 SB 1391 1498 241 (mechanisms ) 247 SB 1638 1498 41 (is ) 47 SB 1685 1498 48 (to ) 54 SB 1739 1498 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111 (used, ) 113 SB 413 1651 188 (including ) 190 SB 603 1651 94 (time ) 96 SB 699 1651 131 (slicing ) 133 SB 832 1651 152 (policies ) 154 SB 986 1651 82 (and ) 85 SB 1071 1651 152 (policies ) 155 SB 1226 1651 119 (based ) 122 SB 1348 1651 58 (on ) 61 SB 1409 1651 69 (the ) 72 SB 1481 1651 216 (probability ) 219 SB 1700 1651 48 (of ) 51 SB 1751 1651 69 (the ) 72 SB 1823 1651 56 (an ) 59 SB 1882 1651 113 (event ) 116 SB 1998 1651 102 (being) 102 SB 300 1702 175 (correctly ) 181 SB 481 1702 188 (executed, ) 194 SB 675 1702 50 (as ) 56 SB 731 1702 193 (estimated ) 199 SB 930 1702 57 (by ) 63 SB 993 1702 109 (some ) 115 SB 1108 1702 183 (heuristic. ) 189 SB 1297 1702 11 ( ) 17 SB 1314 1702 81 (The ) 87 SB 1401 1702 119 (major ) 125 SB 1526 1702 215 (differences ) 221 SB 1747 1702 167 (between ) 173 SB 1920 1702 69 (the ) 75 SB 1995 1702 105 (many) 105 SB 300 1753 140 (correct ) 147 SB 447 1753 214 (scheduling ) 221 SB 668 1753 152 (policies ) 159 SB 827 1753 41 (is ) 48 SB 875 1753 98 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SB 1450 1855 37 (it ) 41 SB 1491 1855 82 (will ) 86 SB 1577 1855 116 (never ) 120 SB 1697 1855 224 (indefinitely ) 228 SB 1925 1855 113 (delay ) 117 SB 2042 1855 58 (the) 58 SB 300 1906 758 (lowest timestamped event in the system.) 758 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 2007 459 (3.1.3 Non-Determinism) 459 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 2109 49 (In ) 54 SB 354 2109 127 (many, ) 132 SB 486 2109 144 (though ) 149 SB 635 2109 72 (not ) 77 SB 712 2109 215 (necessarily ) 221 SB 933 2109 67 (all, ) 73 SB 1006 2109 218 (distributed ) 224 SB 1230 2109 170 (systems, ) 176 SB 1406 2109 248 (determinism ) 254 SB 1660 2109 41 (is ) 47 SB 1707 2109 180 (desirable ) 186 SB 1893 2109 46 (at ) 52 SB 1945 2109 69 (the ) 75 SB 2020 2109 80 (user) 80 SB 300 2160 410 (level. 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261 SB 1932 2415 11 ( ) 13 SB 1945 2415 108 (Also, ) 110 SB 2055 2415 45 (all) 45 SB 300 2466 142 (buffers ) 151 SB 451 2466 82 (and ) 92 SB 543 2466 93 (data ) 103 SB 646 2466 198 (structures ) 208 SB 854 2466 139 (should ) 149 SB 1003 2466 54 (be ) 64 SB 1067 2466 173 (properly ) 183 SB 1250 2466 146 (cleared ) 156 SB 1406 2466 128 (before ) 138 SB 1544 2466 113 (being ) 123 SB 1667 2466 195 (presented ) 205 SB 1872 2466 48 (to ) 58 SB 1930 2466 69 (the ) 79 SB 2009 2466 91 (user.) 91 SB 300 2517 215 (Otherwise, ) 229 SB 529 2517 246 (uninitialized ) 260 SB 789 2517 159 (garbage ) 173 SB 962 2517 75 (can ) 89 SB 1051 2517 114 (cause ) 128 SB 1179 2517 56 (an ) 70 SB 1249 2517 113 (event ) 127 SB 1376 2517 48 (to ) 62 SB 1438 2517 166 (produce ) 180 SB 1618 2517 172 (different ) 187 SB 1805 2517 135 (results ) 150 SB 1955 2517 58 (on ) 73 SB 2028 2517 72 (two) 72 SB 300 2568 172 (different ) 186 SB 486 2568 106 (runs. ) 120 SB 606 2568 11 ( ) 26 SB 632 2568 216 (Experience ) 231 SB 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147 SB 1863 1345 237 (performance) 237 SB 300 1396 194 (can suffer.) 194 SB 300 1497 81 (The ) 88 SB 388 1497 163 (primary ) 170 SB 558 1497 182 (difficulty ) 189 SB 747 1497 47 (in ) 54 SB 801 1497 213 (calculating ) 220 SB 1021 1497 99 (GVT ) 106 SB 1127 1497 41 (is ) 48 SB 1175 1497 174 (ensuring ) 181 SB 1356 1497 84 (that ) 92 SB 1448 1497 32 (a ) 40 SB 1488 1497 197 (consistent ) 205 SB 1693 1497 178 (snapshot ) 186 SB 1879 1497 48 (of ) 56 SB 1935 1497 69 (the ) 77 SB 2012 1497 88 (GVT) 88 SB 300 1548 259 (contributions ) 268 SB 568 1548 48 (of ) 57 SB 625 1548 115 (every ) 124 SB 749 1548 104 (node ) 114 SB 863 1548 41 (is ) 51 SB 914 1548 126 (made. ) 136 SB 1050 1548 11 ( ) 21 SB 1071 1548 160 (Because ) 170 SB 1241 1548 37 (it ) 47 SB 1288 1548 41 (is ) 51 SB 1339 1548 32 (a ) 42 SB 1381 1548 218 (distributed ) 228 SB 1609 1548 259 (computation, ) 269 SB 1878 1548 32 (a ) 42 SB 1920 1548 180 (carelessly) 180 SB 300 1599 147 (written ) 153 SB 453 1599 99 (GVT ) 105 SB 558 1599 194 (algorithm ) 200 SB 758 1599 75 (can ) 81 SB 839 1599 70 (fail ) 76 SB 915 1599 48 (to ) 54 SB 969 1599 170 (consider ) 176 SB 1145 1599 32 (a ) 38 SB 1183 1599 168 (message ) 174 SB 1357 1599 87 (sent ) 93 SB 1450 1599 47 (in ) 53 SB 1503 1599 69 (the ) 75 SB 1578 1599 144 (middle ) 150 SB 1728 1599 48 (of ) 54 SB 1782 1599 99 (GVT ) 105 SB 1887 1599 213 (calculation,) 213 SB 300 1650 149 (leading ) 150 SB 450 1650 48 (to ) 49 SB 499 1650 56 (an ) 57 SB 556 1650 211 (incorrectly ) 213 SB 769 1650 94 (high ) 96 SB 865 1650 167 (estimate ) 169 SB 1034 1650 48 (of ) 50 SB 1084 1650 110 (GVT. ) 112 SB 1196 1650 11 ( ) 13 SB 1209 1650 176 ([Bellenot ) 178 SB 1387 1650 67 (90] ) 69 SB 1456 1650 185 (discusses ) 187 SB 1643 1650 109 (some ) 111 SB 1754 1650 48 (of ) 50 SB 1804 1650 69 (the ) 71 SB 1875 1650 186 (problems ) 188 SB 2063 1650 37 (of) 37 SB 300 1701 1375 (correctly estimating GVT and presents an efficient algorithm for doing so.) 1375 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 1802 1230 (3.2 Performance Issues for Optimistic Synchronization Systems) 1230 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 1904 207 (Optimistic ) 212 SB 512 1904 310 (synchronization ) 315 SB 827 1904 159 (systems ) 164 SB 991 1904 75 (can ) 80 SB 1071 1904 151 (achieve ) 156 SB 1227 1904 95 (very ) 100 SB 1327 1904 106 (good ) 111 SB 1438 1904 259 (performance. ) 264 SB 1702 1904 11 ( ) 16 SB 1718 1904 68 (On ) 74 SB 1792 1904 138 (certain ) 144 SB 1936 1904 164 (irregular) 164 SB 300 1955 238 (simulations, ) 239 SB 539 1955 134 (TWOS ) 135 SB 674 1955 74 (has ) 75 SB 749 1955 177 (achieved ) 178 SB 927 1955 188 (speedups ) 189 SB 1116 1955 47 (in ) 48 SB 1164 1955 128 (excess ) 129 SB 1293 1955 48 (of ) 49 SB 1342 1955 53 (30 ) 54 SB 1396 1955 72 (\(on ) 73 SB 1469 1955 53 (72 ) 55 SB 1524 1955 147 (nodes\), ) 149 SB 1673 1955 125 (which ) 127 SB 1800 1955 41 (is ) 43 SB 1843 1955 128 (nearly ) 130 SB 1973 1955 88 (60% ) 90 SB 2063 1955 37 (of) 37 SB 300 2006 69 (the ) 72 SB 372 2006 242 (theoretically ) 245 SB 617 2006 177 (available ) 180 SB 797 2006 181 (speedup, ) 184 SB 981 2006 50 (as ) 54 SB 1035 2006 227 (determined ) 231 SB 1266 2006 57 (by ) 61 SB 1327 2006 137 (critical ) 141 SB 1468 2006 95 (path ) 99 SB 1567 2006 160 (analysis ) 164 SB 1731 2006 160 ([Presley ) 164 SB 1895 2006 78 (89]. ) 82 SB 1977 2006 11 ( ) 15 SB 1992 2006 108 (Other) 108 SB 300 2057 157 (discrete ) 163 SB 463 2057 113 (event ) 119 SB 582 2057 209 (simulation ) 215 SB 797 2057 241 (mechanisms ) 247 SB 1044 2057 100 (have ) 106 SB 1150 2057 72 (not ) 78 SB 1228 2057 98 (been ) 105 SB 1333 2057 87 (able ) 94 SB 1427 2057 48 (to ) 55 SB 1482 2057 151 (achieve ) 158 SB 1640 2057 229 (comparable ) 236 SB 1876 2057 170 (speedup ) 177 SB 2053 2057 47 (on) 47 SB 300 2108 140 (similar ) 152 SB 452 2108 238 (simulations. ) 250 SB 702 2108 11 ( ) 23 SB 725 2108 196 (However, ) 208 SB 933 2108 248 (performance ) 260 SB 1193 2108 48 (of ) 60 SB 1253 2108 79 (this ) 91 SB 1344 2108 135 (caliber ) 147 SB 1491 2108 41 (is ) 53 SB 1544 2108 129 (highly ) 141 SB 1685 2108 210 (dependent ) 222 SB 1907 2108 58 (on ) 70 SB 1977 2108 123 (design) 123 SB 300 2159 157 (choices. ) 161 SB 461 2159 11 ( ) 15 SB 476 2159 99 (Poor ) 103 SB 579 2159 146 (choices ) 150 SB 729 2159 75 (can ) 79 SB 808 2159 176 (diminish ) 180 SB 988 2159 259 (performance, ) 263 SB 1251 2159 51 (or ) 55 SB 1306 2159 98 (limit ) 102 SB 1408 2159 69 (the ) 73 SB 1481 2159 154 (domain ) 158 SB 1639 2159 48 (of ) 53 SB 1692 2159 237 (applications ) 242 SB 1934 2159 47 (in ) 52 SB 1986 2159 114 (which) 114 SB 300 2210 572 (good performance is achieved.) 572 SB 300 2311 44 (A ) 53 SB 353 2311 119 (major ) 128 SB 481 2311 119 (factor ) 128 SB 609 2311 47 (in ) 56 SB 665 2311 187 (obtaining ) 196 SB 861 2311 106 (good ) 115 SB 976 2311 248 (performance ) 257 SB 1233 2311 41 (is ) 50 SB 1283 2311 197 (overhead, ) 206 SB 1489 2311 50 (as ) 59 SB 1548 2311 37 (it ) 46 SB 1594 2311 41 (is ) 50 SB 1644 2311 65 (for ) 75 SB 1719 2311 79 (any ) 89 SB 1808 2311 152 (system. ) 162 SB 1970 2311 11 ( ) 21 SB 1991 2311 109 (Usual) 109 SB 300 2362 173 (methods ) 184 SB 484 2362 65 (for ) 76 SB 560 2362 225 (minimizing ) 236 SB 796 2362 186 (overhead ) 197 SB 993 2362 139 (should ) 150 SB 1143 2362 85 (also ) 96 SB 1239 2362 54 (be ) 66 SB 1305 2362 152 (applied ) 164 SB 1469 2362 48 (to ) 60 SB 1529 2362 69 (the ) 81 SB 1610 2362 134 (design ) 146 SB 1756 2362 82 (and ) 94 SB 1850 2362 133 (tuning ) 145 SB 1995 2362 48 (of ) 60 SB 2055 2362 45 (an) 45 SB 300 2413 197 (optimistic ) 212 SB 512 2413 310 (synchronization ) 325 SB 837 2413 152 (system. ) 167 SB 1004 2413 11 ( ) 27 SB 1031 2413 11 ( ) 27 SB 1058 2413 11 ( ) 27 SB 1085 2413 196 (However, ) 212 SB 1297 2413 197 (optimistic ) 213 SB 1510 2413 310 (synchronization ) 326 SB 1836 2413 159 (systems ) 175 SB 2011 2413 89 (have) 89 SB 300 2464 204 (overheads ) 205 SB 505 2464 72 (not ) 73 SB 578 2464 149 (present ) 150 SB 728 2464 47 (in ) 48 SB 776 2464 109 (other ) 110 SB 886 2464 218 (distributed ) 219 SB 1105 2464 170 (systems, ) 171 SB 1276 2464 82 (and ) 83 SB 1359 2464 107 (these ) 108 SB 1467 2464 204 (overheads ) 206 SB 1673 2464 105 (must ) 107 SB 1780 2464 54 (be ) 56 SB 1836 2464 223 (minimized, ) 225 SB 2061 2464 39 (as) 39 SB 300 2515 90 (well.) 90 SB 300 2616 49 (In ) 53 SB 353 2616 169 (addition ) 173 SB 526 2616 48 (to ) 52 SB 578 2616 186 (overhead ) 190 SB 768 2616 293 (considerations, ) 297 SB 1065 2616 109 (other ) 113 SB 1178 2616 134 (design ) 139 SB 1317 2616 146 (choices ) 151 SB 1468 2616 47 (in ) 52 SB 1520 2616 225 (scheduling, ) 230 SB 1750 2616 168 (message ) 173 SB 1923 2616 177 (handling,) 177 SB 300 2667 82 (and ) 87 SB 387 2667 168 (memory ) 173 SB 560 2667 252 (management ) 257 SB 817 2667 75 (can ) 80 SB 897 2667 100 (have ) 106 SB 1003 2667 139 (impact ) 145 SB 1148 2667 58 (on ) 64 SB 1212 2667 69 (the ) 75 SB 1287 2667 248 (performance ) 254 SB 1541 2667 48 (of ) 54 SB 1595 2667 69 (the ) 75 SB 1670 2667 152 (system. ) 158 SB 1828 2667 11 ( ) 17 SB 1845 2667 154 (Making ) 160 SB 2005 2667 95 (good) 95 SB 300 2718 146 (choices ) 148 SB 448 2718 51 (or ) 53 SB 501 2718 99 (poor ) 101 SB 602 2718 146 (choices ) 148 SB 750 2718 92 (here ) 95 SB 845 2718 75 (can ) 78 SB 923 2718 113 (mean ) 116 SB 1039 2718 69 (the ) 72 SB 1111 2718 197 (difference ) 200 SB 1311 2718 167 (between ) 170 SB 1481 2718 106 (good ) 109 SB 1590 2718 248 (performance ) 251 SB 1841 2718 82 (and ) 85 SB 1926 2718 174 (mediocre) 174 SB 300 2769 248 (performance.) 248 SB 1 #C statusdict begin /manualfeed false store end EJ RS %%PageTrailer %%PageResources: font Palatino-Bold %%+ font Palatino-Roman %%Page: 9 9 %%PageResources: (atend) SS 0 0 25 25 798 1100 300 SM 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 0 0 0 fC 300 225 149 (Finally, ) 154 SB 454 225 69 (the ) 74 SB 528 225 197 (optimistic ) 202 SB 730 225 190 (execution ) 195 SB 925 225 193 (paradigm ) 198 SB 1123 225 74 (has ) 79 SB 1202 225 138 (certain ) 144 SB 1346 225 249 (optimization ) 255 SB 1601 225 241 (possibilities. ) 247 SB 1848 225 11 ( ) 17 SB 1865 225 119 (These ) 125 SB 1990 225 110 (rarely) 110 SB 300 276 1432 (allow major gains in performance, but they can be worthwhile in some cases.) 1432 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 377 1063 (3.2.1 Overhead in Optimistic Synchronization Systems) 1063 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 479 1659 (There are several components of overhead in optimistic execution systems. They include) 1659 SB 450 580 25 (\225) 25 SB 475 580 526 ( Message sending overhead) 526 SB 450 681 25 (\225) 25 SB 475 681 369 ( Rollback overhead) 369 SB 450 782 25 (\225) 25 SB 475 782 432 ( State saving overhead) 432 SB 450 883 25 (\225) 25 SB 475 883 509 ( GVT calculation overhead) 509 SB 300 984 1107 (The following sections discuss these overhead components.) 1107 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 1085 678 (3.2.1.1 Message Sending Overhead) 678 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 1187 171 (Message ) 180 SB 480 1187 158 (sending ) 167 SB 647 1187 186 (overhead ) 195 SB 842 1187 41 (is ) 50 SB 892 1187 32 (a ) 41 SB 933 1187 119 (major ) 128 SB 1061 1187 220 (component ) 230 SB 1291 1187 48 (of ) 58 SB 1349 1187 69 (the ) 79 SB 1428 1187 95 (total ) 105 SB 1533 1187 186 (overhead ) 196 SB 1729 1187 48 (of ) 58 SB 1787 1187 145 (TWOS. ) 155 SB 1942 1187 11 ( ) 21 SB 1963 1187 137 (Objects) 137 SB 300 1238 262 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1340 39 (If ) 53 SB 1433 1340 69 (the ) 83 SB 1516 1340 319 (communications ) 333 SB 1849 1340 207 (subsystem ) 221 SB 2070 1340 30 (is) 30 SB 300 1391 281 (asynchronous, ) 282 SB 582 1391 50 (as ) 51 SB 633 1391 37 (it ) 38 SB 671 1391 41 (is ) 42 SB 713 1391 65 (for ) 66 SB 779 1391 145 (TWOS, ) 146 SB 925 1391 144 (latency ) 145 SB 1070 1391 41 (is ) 42 SB 1112 1391 48 (of ) 49 SB 1161 1391 203 (somewhat ) 204 SB 1365 1391 79 (less ) 80 SB 1445 1391 157 (concern ) 158 SB 1603 1391 94 (than ) 95 SB 1698 1391 210 (processing ) 212 SB 1910 1391 105 (time. ) 107 SB 2017 1391 11 ( ) 13 SB 2030 1391 70 (The) 70 SB 300 1442 136 (sender ) 141 SB 441 1442 98 (does ) 103 SB 544 1442 72 (not ) 77 SB 621 1442 122 (block, ) 127 SB 748 1442 82 (and ) 87 SB 835 1442 108 (more ) 113 SB 948 1442 106 (often ) 111 SB 1059 1442 94 (than ) 99 SB 1158 1442 72 (not ) 77 SB 1235 1442 69 (the ) 74 SB 1309 1442 182 (receiving ) 187 SB 1496 1442 191 (processor ) 197 SB 1693 1442 82 (will ) 88 SB 1781 1442 100 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369 1697 165 (delivery ) 169 SB 538 1697 48 (of ) 52 SB 590 1697 56 (an ) 60 SB 650 1697 169 (off-node ) 173 SB 823 1697 168 (message ) 172 SB 995 1697 41 (is ) 45 SB 1040 1697 64 (2.3 ) 68 SB 1108 1697 255 (milliseconds, ) 259 SB 1367 1697 195 (measured ) 199 SB 1566 1697 102 (from ) 107 SB 1673 1697 69 (the ) 74 SB 1747 1697 109 (point ) 114 SB 1861 1697 46 (at ) 51 SB 1912 1697 125 (which ) 130 SB 2042 1697 58 (the) 58 SB 300 1748 168 (message ) 175 SB 475 1748 41 (is ) 49 SB 524 1748 195 (presented ) 203 SB 727 1748 48 (to ) 56 SB 783 1748 146 (TWOS\222 ) 154 SB 937 1748 133 (source ) 141 SB 1078 1748 104 (node ) 112 SB 1190 1748 48 (to ) 56 SB 1246 1748 69 (the ) 77 SB 1323 1748 94 (time ) 102 SB 1425 1748 69 (the ) 77 SB 1502 1748 219 (destination ) 227 SB 1729 1748 104 (node ) 112 SB 1841 1748 93 (puts ) 101 SB 1942 1748 37 (it ) 45 SB 1987 1748 47 (in ) 55 SB 2042 1748 58 (the) 58 SB 300 1799 182 (receiving ) 192 SB 492 1799 150 (object\222s ) 160 SB 652 1799 111 (input ) 121 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(considerably ) 255 SB 2032 2410 68 (less) 68 SB 300 2461 654 (than the cost of sending a message.) 654 SB 300 2562 81 (The ) 97 SB 397 2562 93 (only ) 109 SB 506 2562 88 (part ) 104 SB 610 2562 48 (of ) 64 SB 674 2562 69 (the ) 85 SB 759 2562 161 (rollback ) 177 SB 936 2562 84 (that ) 100 SB 1036 2562 204 (frequently ) 220 SB 1256 2562 74 (has ) 90 SB 1346 2562 204 (significant ) 221 SB 1567 2562 160 (expense ) 177 SB 1744 2562 41 (is ) 58 SB 1802 2562 69 (the ) 86 SB 1888 2562 158 (sending ) 175 SB 2063 2562 37 (of) 37 SB 300 2613 232 (cancellation ) 237 SB 537 2613 197 (messages. ) 202 SB 739 2613 11 ( ) 16 SB 755 2613 49 (In ) 54 SB 809 2613 145 (TWOS, ) 150 SB 959 2613 69 (the ) 74 SB 1033 2613 232 (cancellation ) 237 SB 1270 2613 186 (messages ) 191 SB 1461 2613 69 (are ) 74 SB 1535 2613 151 (already ) 156 SB 1691 2613 216 (completely ) 221 SB 1912 2613 63 (set ) 68 SB 1980 2613 61 (up ) 66 SB 2046 2613 54 (for) 54 SB 300 2664 165 (delivery ) 174 SB 474 2664 47 (in ) 56 SB 530 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2766 11 ( ) 17 SB 815 2766 81 (The ) 87 SB 902 2766 186 (overhead ) 193 SB 1095 2766 48 (of ) 55 SB 1150 2766 158 (sending ) 165 SB 1315 2766 69 (the ) 76 SB 1391 2766 261 (cancellations, ) 268 SB 1659 2766 185 (however, ) 192 SB 1851 2766 41 (is ) 48 SB 1899 2766 136 (almost ) 143 SB 2042 2766 58 (the) 58 SB 300 2817 697 (same as sending the normal message.) 697 SB 1 #C statusdict begin /manualfeed false store end EJ RS %%PageTrailer %%PageResources: font Palatino-Bold %%+ font Palatino-Roman %%Page: 10 10 %%PageResources: (atend) SS 0 0 25 25 798 1100 300 SM 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 0 0 0 fC 300 225 1092 (The dominating overhead cost of a rollback, then, is in the ) 1093 SB 1393 225 158 (sending ) 159 SB 1552 225 48 (of ) 49 SB 1601 225 79 (any ) 80 SB 1681 225 232 (cancellation ) 233 SB 1914 225 186 (messages.) 186 SB 300 276 228 (Minimizing ) 230 SB 530 276 69 (the ) 71 SB 601 276 85 (cost ) 87 SB 688 276 48 (of ) 50 SB 738 276 158 (sending ) 160 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173 (properly ) 178 SB 1849 276 251 (synchronized) 251 SB 300 327 69 (are ) 70 SB 370 327 116 (much ) 117 SB 487 327 129 (lower, ) 130 SB 617 327 82 (and ) 83 SB 700 327 69 (the ) 70 SB 770 327 191 (processor ) 192 SB 962 327 132 (would ) 133 SB 1095 327 54 (be ) 55 SB 1150 327 119 (better ) 120 SB 1270 327 62 (off ) 63 SB 1333 327 183 (spending ) 184 SB 1517 327 55 (its ) 57 SB 1574 327 94 (time ) 96 SB 1670 327 195 (preparing ) 197 SB 1867 327 48 (to ) 50 SB 1917 327 123 (lessen ) 125 SB 2042 327 58 (the) 58 SB 300 378 549 (cost of a fairly likely rollback.) 549 SB 300 479 538 (Some have suggested, in the ) 539 SB 839 479 109 (latter ) 110 SB 949 479 100 (case, ) 101 SB 1050 479 84 (that ) 85 SB 1135 479 69 (the ) 70 SB 1205 479 191 (processor ) 192 SB 1397 479 41 (is ) 42 SB 1439 479 119 (better ) 120 SB 1559 479 62 (off ) 63 SB 1622 479 72 (not ) 73 SB 1695 479 160 (running ) 161 SB 1856 479 56 (an ) 57 SB 1913 479 113 (event ) 114 SB 2027 479 73 (that) 73 SB 300 530 351 (is very 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(small ) 113 SB 1402 632 138 (chance ) 140 SB 1542 632 48 (of ) 50 SB 1592 632 113 (being ) 115 SB 1707 632 140 (correct ) 142 SB 1849 632 41 (is ) 44 SB 1893 632 183 (generally ) 186 SB 2079 632 21 (a) 21 SB 300 683 108 (more ) 120 SB 420 683 216 (productive ) 228 SB 648 683 74 (use ) 86 SB 734 683 48 (of ) 60 SB 794 683 69 (the ) 81 SB 875 683 221 (processor\222s ) 234 SB 1109 683 122 (cycles ) 135 SB 1244 683 94 (than ) 107 SB 1351 683 119 (doing ) 132 SB 1483 683 155 (nothing ) 168 SB 1651 683 46 (at ) 59 SB 1710 683 67 (all. ) 80 SB 1790 683 11 ( ) 24 SB 1814 683 58 (Of ) 71 SB 1885 683 144 (course, ) 157 SB 2042 683 58 (the) 58 SB 300 734 191 (processor ) 196 SB 496 734 41 (is ) 46 SB 542 734 85 (also ) 90 SB 632 734 161 (creating ) 166 SB 798 734 186 (overhead ) 191 SB 989 734 65 (for ) 70 SB 1059 734 109 (other ) 115 SB 1174 734 209 (processors ) 215 SB 1389 734 84 (that ) 90 SB 1479 734 92 (may ) 98 SB 1577 734 100 (have ) 106 SB 1683 734 119 (better ) 125 SB 1808 734 109 (work ) 115 SB 1923 734 48 (to ) 54 SB 1977 734 71 (do, ) 77 SB 2054 734 46 (by) 46 SB 300 785 158 (sending ) 161 SB 461 785 106 (them ) 109 SB 570 785 186 (messages ) 189 SB 759 785 84 (that ) 87 SB 846 785 69 (are ) 72 SB 918 785 110 (fairly ) 114 SB 1032 785 113 (likely ) 117 SB 1149 785 48 (to ) 52 SB 1201 785 54 (be ) 58 SB 1259 785 195 (cancelled. ) 199 SB 1458 785 11 ( ) 15 SB 1473 785 196 (However, ) 200 SB 1673 785 131 (except ) 135 SB 1808 785 47 (in ) 51 SB 1859 785 241 (low-memory) 241 SB 300 836 203 (situations, ) 207 SB 507 836 110 (those ) 114 SB 621 836 103 (costs ) 107 SB 728 836 106 (seem ) 110 SB 838 836 48 (to ) 52 SB 890 836 54 (be ) 58 SB 948 836 114 (offset ) 118 SB 1066 836 57 (by ) 61 SB 1127 836 69 (the ) 74 SB 1201 836 138 (benefit ) 143 SB 1344 836 48 (of ) 53 SB 1397 836 238 (occasionally ) 243 SB 1640 836 160 (running ) 165 SB 1805 836 32 (a ) 37 SB 1842 836 140 (correct ) 145 SB 1987 836 113 (event.) 113 SB 300 887 1111 (This issue will be discussed in more detail in section 3.3.2.3.) 1111 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 988 668 (3.2.1.4 GVT Calculation Overhead) 668 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 1090 81 (The ) 84 SB 384 1090 163 (primary ) 166 SB 550 1090 164 (purpose ) 167 SB 717 1090 48 (of ) 51 SB 768 1090 213 (calculating ) 216 SB 984 1090 99 (GVT ) 102 SB 1086 1090 41 (is ) 44 SB 1130 1090 48 (to ) 51 SB 1181 1090 136 (permit ) 139 SB 1320 1090 69 (the ) 72 SB 1392 1090 141 (system ) 144 SB 1536 1090 48 (to ) 51 SB 1587 1090 108 (fossil ) 112 SB 1699 1090 130 (collect ) 134 SB 1833 1090 72 (old ) 76 SB 1909 1090 116 (states ) 120 SB 2029 1090 71 (and) 71 SB 300 1141 186 (messages ) 200 SB 500 1141 58 (no ) 72 SB 572 1141 130 (longer ) 144 SB 716 1141 147 (needed ) 161 SB 877 1141 48 (to ) 62 SB 939 1141 158 (support ) 172 SB 1111 1141 162 (possible ) 176 SB 1287 1141 190 (rollbacks. ) 205 SB 1492 1141 11 ( ) 26 SB 1518 1141 81 (The ) 96 SB 1614 1141 108 (more ) 123 SB 1737 1141 204 (frequently ) 219 SB 1956 1141 99 (GVT ) 114 SB 2070 1141 30 (is) 30 SB 300 1192 211 (calculated, ) 212 SB 512 1192 69 (the ) 70 SB 582 1192 151 (quicker ) 153 SB 735 1192 97 (such ) 99 SB 834 1192 124 (items\222 ) 126 SB 960 1192 168 (memory ) 170 SB 1130 1192 41 (is ) 43 SB 1173 1192 174 (returned ) 176 SB 1349 1192 48 (to ) 50 SB 1399 1192 69 (the ) 71 SB 1470 1192 101 (heap ) 103 SB 1573 1192 65 (for ) 67 SB 1640 1192 74 (use ) 76 SB 1716 1192 57 (by ) 59 SB 1775 1192 109 (other ) 111 SB 1886 1192 142 (events. ) 144 SB 2030 1192 11 ( ) 13 SB 2043 1192 57 (On) 57 SB 300 1243 69 (the ) 79 SB 379 1243 109 (other ) 119 SB 498 1243 117 (hand, ) 127 SB 625 1243 69 (the ) 79 SB 704 1243 99 (GVT ) 109 SB 813 1243 194 (algorithm ) 204 SB 1017 1243 164 (requires ) 174 SB 1191 1243 168 (multiple ) 179 SB 1370 1243 137 (phases ) 148 SB 1518 1243 48 (of ) 59 SB 1577 1243 168 (message ) 179 SB 1756 1243 128 (sends, ) 139 SB 1895 1243 96 (with ) 107 SB 2002 1243 98 (some) 98 SB 300 1294 231 (calculations ) 239 SB 539 1294 58 (on ) 66 SB 605 1294 95 (each ) 104 SB 709 1294 104 (node ) 113 SB 822 1294 48 (to ) 57 SB 879 1294 201 (determine ) 210 SB 1089 1294 98 (local ) 107 SB 1196 1294 259 (contributions ) 268 SB 1464 1294 48 (to ) 57 SB 1521 1294 110 (GVT. ) 119 SB 1640 1294 11 ( ) 20 SB 1660 1294 103 (With ) 112 SB 1772 1294 99 (GVT ) 108 SB 1880 1294 220 (calculations) 220 SB 300 1345 1599 (performed every second, the existing TWOS GVT algorithm spends considerably less ) 1600 SB 1900 1345 94 (than ) 95 SB 1995 1345 67 (1% ) 68 SB 2063 1345 37 (of) 37 SB 300 1396 69 (the ) 81 SB 381 1396 95 (total ) 107 SB 488 1396 190 (execution ) 202 SB 690 1396 94 (time ) 106 SB 796 1396 48 (of ) 60 SB 856 1396 69 (the ) 81 SB 937 1396 141 (system ) 153 SB 1090 1396 160 (running ) 172 SB 1262 1396 243 (GVT-related ) 255 SB 1517 1396 110 (code. ) 122 SB 1639 1396 11 ( ) 23 SB 1662 1396 68 (An ) 80 SB 1742 1396 141 (earlier, ) 154 SB 1896 1396 79 (less ) 92 SB 1988 1396 112 (clever) 112 SB 300 1447 205 (algorithm, ) 218 SB 518 1447 125 (which ) 138 SB 656 1447 100 (used ) 113 SB 769 1447 248 (substantially ) 261 SB 1030 1447 108 (more ) 121 SB 1151 1447 186 (messages ) 199 SB 1350 1447 82 (and ) 95 SB 1445 1447 130 (longer ) 143 SB 1588 1447 131 (delays ) 144 SB 1732 1447 47 (in ) 60 SB 1792 1447 224 (calculation, ) 237 SB 2029 1447 71 (had) 71 SB 300 1498 147 (around ) 148 SB 448 1498 32 (a ) 33 SB 481 1498 67 (1% ) 68 SB 549 1498 139 (impact ) 140 SB 689 1498 58 (on ) 59 SB 748 1498 69 (the ) 71 SB 819 1498 95 (total ) 97 SB 916 1498 153 (elapsed ) 155 SB 1071 1498 94 (time ) 96 SB 1167 1498 48 (of ) 50 SB 1217 1498 137 (typical ) 139 SB 1356 1498 238 (simulations, ) 240 SB 1596 1498 211 (suggesting ) 213 SB 1809 1498 84 (that ) 86 SB 1895 1498 99 (even ) 101 SB 1996 1498 32 (a ) 34 SB 2030 1498 70 (bad) 70 SB 300 1549 1699 (GVT algorithm will not have terrible effects on the performance of the system [Bellenot 90].) 1699 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 1650 1450 (3.2.2 Performance Design Choices For Optimistic Synchronization Systems) 1450 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 1752 113 (Some ) 119 SB 419 1752 48 (of ) 54 SB 473 1752 69 (the ) 75 SB 548 1752 134 (design ) 140 SB 688 1752 146 (choices ) 152 SB 840 1752 65 (for ) 71 SB 911 1752 56 (an ) 63 SB 974 1752 197 (optimistic ) 204 SB 1178 1752 310 (synchronization ) 317 SB 1495 1752 141 (system ) 148 SB 1643 1752 84 (that ) 91 SB 1734 1752 75 (can ) 82 SB 1816 1752 100 (have ) 107 SB 1923 1752 177 (profound) 177 SB 300 1803 585 (effects on performance include:) 585 SB 450 1904 25 (\225) 25 SB 475 1904 709 ( Scheduling and Priority Mechanisms) 709 SB 450 2005 25 (\225) 25 SB 475 2005 629 ( Memory Management Strategies) 629 SB 450 2106 25 (\225) 25 SB 475 2106 652 ( Load Management and Migration) 652 SB 300 2207 1076 (The following sections discuss these issues in more detail.) 1076 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 2308 856 (3.2.2.1 Scheduling and Priority Mechanisms) 856 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 2410 81 (The ) 89 SB 389 2410 136 (virtual ) 144 SB 533 2410 94 (time ) 102 SB 635 2410 87 (tags ) 96 SB 731 2410 100 (used ) 109 SB 840 2410 47 (in ) 56 SB 896 2410 197 (optimistic ) 206 SB 1102 2410 190 (execution ) 199 SB 1301 2410 159 (systems ) 168 SB 1469 2410 110 (serve ) 119 SB 1588 2410 50 (as ) 59 SB 1647 2410 123 (rough ) 132 SB 1779 2410 197 (indicators ) 206 SB 1985 2410 48 (of ) 57 SB 2042 2410 58 (the) 58 SB 300 2461 1260 (priority of events and messages, and as equally rough indicators of ) 1261 SB 1561 2461 69 (the ) 70 SB 1631 2461 216 (probability ) 217 SB 1848 2461 48 (of ) 49 SB 1897 2461 131 (events ) 132 SB 2029 2461 71 (and) 71 SB 300 2512 186 (messages ) 199 SB 499 2512 113 (being ) 126 SB 625 2512 151 (correct. ) 164 SB 789 2512 11 ( ) 24 SB 813 2512 68 (An ) 81 SB 894 2512 198 (important ) 211 SB 1105 2512 172 (heuristic ) 185 SB 1290 2512 65 (for ) 79 SB 1369 2512 141 (getting ) 155 SB 1524 2512 106 (good ) 120 SB 1644 2512 248 (performance ) 262 SB 1906 2512 73 (out ) 87 SB 1993 2512 48 (of ) 62 SB 2055 2512 45 (an) 45 SB 300 2563 197 (optimistic ) 203 SB 503 2563 190 (execution ) 196 SB 699 2563 141 (system ) 147 SB 846 2563 41 (is ) 47 SB 893 2563 48 (to ) 54 SB 947 2563 110 (favor ) 116 SB 1063 2563 208 (operations ) 214 SB 1277 2563 96 (with ) 102 SB 1379 2563 81 (low ) 87 SB 1466 2563 136 (virtual ) 142 SB 1608 2563 94 (time ) 100 SB 1708 2563 87 (tags ) 93 SB 1801 2563 95 (over ) 102 SB 1903 2563 197 (operations) 197 SB 300 2614 507 (with high virtual time tags.) 507 SB 300 2715 62 (As ) 72 SB 372 2715 193 (discussed ) 203 SB 575 2715 47 (in ) 57 SB 632 2715 141 (section ) 151 SB 783 2715 75 (3.1, ) 85 SB 868 2715 116 (many ) 126 SB 994 2715 192 (scheduler ) 202 SB 1196 2715 152 (policies ) 162 SB 1358 2715 75 (can ) 85 SB 1443 2715 90 (give ) 100 SB 1543 2715 140 (correct ) 150 SB 1693 2715 135 (results ) 145 SB 1838 2715 65 (for ) 76 SB 1914 2715 186 (optimistic) 186 SB 300 2766 190 (execution ) 196 SB 496 2766 170 (systems. ) 176 SB 672 2766 11 ( ) 17 SB 689 2766 196 (However, ) 202 SB 891 2766 69 (the ) 75 SB 966 2766 125 (policy ) 131 SB 1097 2766 84 (that ) 90 SB 1187 2766 74 (has ) 80 SB 1267 2766 114 (given ) 120 SB 1387 2766 69 (the ) 75 SB 1462 2766 86 (best ) 92 SB 1554 2766 135 (results ) 141 SB 1695 2766 65 (for ) 72 SB 1767 2766 145 (TWOS, ) 152 SB 1919 2766 82 (and ) 89 SB 2008 2766 92 (most) 92 SB 300 2817 109 (other ) 114 SB 414 2817 197 (optimistic ) 202 SB 616 2817 190 (execution ) 195 SB 811 2817 152 (system, ) 157 SB 968 2817 41 (is ) 46 SB 1014 2817 225 (preemptive ) 231 SB 1245 2817 133 (lowest ) 139 SB 1384 2817 136 (virtual ) 142 SB 1526 2817 94 (time ) 100 SB 1626 2817 113 (event ) 119 SB 1745 2817 97 (first. ) 103 SB 1848 2817 11 ( ) 17 SB 1865 2817 173 ([Burdorf ) 179 SB 2044 2817 56 (90]) 56 SB 300 2868 239 (investigated ) 266 SB 566 2868 109 (some ) 136 SB 702 2868 194 (particular ) 222 SB 924 2868 107 (cases ) 135 SB 1059 2868 65 (for ) 93 SB 1152 2868 151 (various ) 179 SB 1331 2868 214 (scheduling ) 242 SB 1573 2868 152 (policies ) 180 SB 1753 2868 123 (under ) 151 SB 1904 2868 69 (the ) 97 SB 2001 2868 99 (Rand) 99 SB 1 #C statusdict begin /manualfeed false store end EJ RS %%PageTrailer %%PageResources: font Palatino-Bold %%+ font Palatino-Roman %%Page: 12 12 %%PageResources: (atend) SS 0 0 25 25 798 1100 300 SM 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 0 0 0 fC 300 225 306 (implementation ) 315 SB 615 225 48 (of ) 57 SB 672 225 106 (Time ) 115 SB 787 225 127 (Warp, ) 136 SB 923 225 82 (and ) 91 SB 1014 225 123 (found ) 132 SB 1146 225 84 (that ) 93 SB 1239 225 58 (no ) 67 SB 1306 225 123 (tested ) 132 SB 1438 225 125 (policy ) 134 SB 1572 225 75 (did ) 85 SB 1657 225 95 (very ) 105 SB 1762 225 116 (much ) 126 SB 1888 225 119 (better ) 129 SB 2017 225 83 (than) 83 SB 300 276 133 (lowest ) 134 SB 434 276 136 (virtual ) 137 SB 571 276 94 (time ) 95 SB 666 276 97 (first. ) 98 SB 764 276 11 ( ) 12 SB 776 276 118 (There ) 119 SB 895 276 41 (is ) 42 SB 937 276 32 (a ) 34 SB 971 276 168 (superior ) 170 SB 1141 276 136 (policy, ) 138 SB 1279 276 185 (however. ) 187 SB 1466 276 11 ( ) 13 SB 1479 276 150 (Ideally, ) 152 SB 1631 276 69 (the ) 71 SB 1702 276 91 (next ) 93 SB 1795 276 113 (event ) 115 SB 1910 276 190 (scheduled) 190 SB 300 327 57 (by ) 59 SB 359 327 95 (each ) 97 SB 456 327 104 (node ) 106 SB 562 327 139 (should ) 141 SB 703 327 54 (be ) 56 SB 759 327 69 (the ) 71 SB 830 327 113 (event ) 115 SB 945 327 96 (least ) 98 SB 1043 327 113 (likely ) 115 SB 1158 327 48 (to ) 50 SB 1208 327 54 (be ) 56 SB 1264 327 121 (rolled ) 123 SB 1387 327 108 (back. ) 110 SB 1497 327 11 ( ) 13 SB 1510 327 62 (As ) 64 SB 1574 327 79 (yet, ) 81 SB 1655 327 133 (lowest ) 135 SB 1790 327 136 (virtual ) 138 SB 1928 327 94 (time ) 97 SB 2025 327 75 (first) 75 SB 300 378 41 (is ) 48 SB 348 378 69 (the ) 77 SB 425 378 86 (best ) 94 SB 519 378 172 (heuristic ) 180 SB 699 378 140 (known ) 148 SB 847 378 65 (for ) 73 SB 920 378 206 (estimating ) 214 SB 1134 378 69 (the ) 77 SB 1211 378 216 (probability ) 224 SB 1435 378 48 (of ) 56 SB 1491 378 140 (correct ) 148 SB 1639 378 201 (execution. ) 209 SB 1848 378 11 ( ) 19 SB 1867 378 178 (Research ) 186 SB 2053 378 47 (on) 47 SB 300 429 779 (better heuristics is ongoing [Steinman 92].) 779 SB 300 530 138 (Giving ) 141 SB 441 530 207 (preference ) 210 SB 651 530 48 (to ) 51 SB 702 530 81 (low ) 84 SB 786 530 136 (virtual ) 139 SB 925 530 94 (time ) 98 SB 1023 530 112 (items ) 116 SB 1139 530 41 (is ) 45 SB 1184 530 100 (used ) 104 SB 1288 530 240 (heuristically ) 244 SB 1532 530 223 (throughout ) 227 SB 1759 530 134 (TWOS ) 138 SB 1897 530 48 (to ) 52 SB 1949 530 151 (increase) 151 SB 300 581 259 (performance. ) 264 SB 564 581 11 ( ) 16 SB 580 581 203 (Generally, ) 208 SB 788 581 69 (the ) 74 SB 862 581 118 (lower ) 123 SB 985 581 69 (the ) 74 SB 1059 581 136 (virtual ) 141 SB 1200 581 94 (time ) 99 SB 1299 581 69 (tag ) 74 SB 1373 581 58 (on ) 63 SB 1436 581 56 (an ) 61 SB 1497 581 105 (item, ) 110 SB 1607 581 69 (the ) 74 SB 1681 581 108 (more ) 113 SB 1794 581 113 (likely ) 119 SB 1913 581 37 (it ) 43 SB 1956 581 41 (is ) 47 SB 2003 581 48 (to ) 54 SB 2057 581 43 (be) 43 SB 300 632 140 (correct ) 143 SB 443 632 82 (and ) 85 SB 528 632 69 (the ) 72 SB 600 632 108 (more ) 111 SB 711 632 113 (likely ) 116 SB 827 632 37 (it ) 40 SB 867 632 41 (is ) 44 SB 911 632 84 (that ) 87 SB 998 632 172 (delaying ) 175 SB 1173 632 37 (it ) 40 SB 1213 632 82 (will ) 85 SB 1298 632 114 (cause ) 117 SB 1415 632 176 (incorrect ) 179 SB 1594 632 190 (execution ) 193 SB 1787 632 84 (that ) 87 SB 1874 632 82 (will ) 85 SB 1959 632 100 (have ) 104 SB 2063 632 37 (to) 37 SB 300 683 54 (be ) 57 SB 357 683 121 (rolled ) 124 SB 481 683 108 (back. ) 111 SB 592 683 11 ( ) 14 SB 606 683 203 (Therefore, ) 206 SB 812 683 168 (message ) 171 SB 983 683 160 (routing, ) 163 SB 1146 683 168 (memory ) 171 SB 1317 683 263 (management, ) 266 SB 1583 683 82 (and ) 86 SB 1669 683 109 (other ) 113 SB 1782 683 141 (system ) 145 SB 1927 683 173 (functions) 173 SB 300 734 69 (are ) 77 SB 377 734 56 (all ) 64 SB 441 734 134 (driven ) 142 SB 583 734 57 (by ) 65 SB 648 734 238 (timestamps. ) 246 SB 894 734 11 ( ) 19 SB 913 734 44 (A ) 52 SB 965 734 168 (message ) 176 SB 1141 734 96 (with ) 104 SB 1245 734 32 (a ) 40 SB 1285 734 81 (low ) 89 SB 1374 734 209 (timestamp ) 217 SB 1591 734 82 (will ) 91 SB 1682 734 54 (be ) 63 SB 1745 734 188 (delivered ) 197 SB 1942 734 128 (before ) 137 SB 2079 734 21 (a) 21 SB 300 785 168 (message ) 172 SB 472 785 96 (with ) 100 SB 572 785 32 (a ) 37 SB 609 785 94 (high ) 99 SB 708 785 220 (timestamp. ) 225 SB 933 785 11 ( ) 16 SB 949 785 49 (In ) 54 SB 1003 785 98 (tight ) 103 SB 1106 785 168 (memory ) 173 SB 1279 785 203 (situations, ) 208 SB 1487 785 32 (a ) 37 SB 1524 785 149 (request ) 154 SB 1678 785 96 (with ) 101 SB 1779 785 32 (a ) 37 SB 1816 785 81 (low ) 86 SB 1902 785 198 (timestamp) 198 SB 300 836 1164 (will be given preference over a request with a high timestamp.) 1164 SB 300 937 154 (Priority ) 156 SB 456 937 139 (should ) 142 SB 598 937 85 (also ) 88 SB 686 937 54 (be ) 57 SB 743 937 114 (given ) 117 SB 860 937 48 (to ) 51 SB 911 937 169 (negative ) 172 SB 1083 937 168 (message ) 171 SB 1254 937 133 (traffic. ) 136 SB 1390 937 11 ( ) 14 SB 1404 937 180 (Negative ) 183 SB 1587 937 186 (messages ) 189 SB 1776 937 69 (are ) 72 SB 1848 937 87 (sent ) 90 SB 1938 937 114 (when ) 117 SB 2055 937 45 (an) 45 SB 300 988 1282 (event is rolled back and TWOS needs to cancel the messages it sent. ) 1283 SB 1583 988 101 (Such ) 102 SB 1685 988 169 (negative ) 170 SB 1855 988 186 (messages ) 187 SB 2042 988 58 (are) 58 SB 300 1039 138 (certain ) 151 SB 451 1039 197 (indicators ) 210 SB 661 1039 84 (that ) 97 SB 758 1039 98 (their ) 111 SB 869 1039 282 (corresponding ) 295 SB 1164 1039 159 (positive ) 173 SB 1337 1039 186 (messages ) 200 SB 1537 1039 69 (are ) 83 SB 1620 1039 187 (incorrect, ) 201 SB 1821 1039 52 (so ) 66 SB 1887 1039 79 (any ) 93 SB 1980 1039 120 (events) 120 SB 300 1090 210 (performed ) 219 SB 519 1090 57 (by ) 66 SB 585 1090 110 (those ) 119 SB 704 1090 159 (positive ) 168 SB 872 1090 186 (messages ) 195 SB 1067 1090 69 (are ) 78 SB 1145 1090 138 (certain ) 147 SB 1292 1090 48 (to ) 57 SB 1349 1090 54 (be ) 63 SB 1412 1090 121 (rolled ) 130 SB 1542 1090 108 (back. ) 117 SB 1659 1090 11 ( ) 20 SB 1679 1090 203 (Therefore, ) 212 SB 1891 1090 141 (getting ) 151 SB 2042 1090 58 (the) 58 SB 300 1141 169 (negative ) 174 SB 474 1141 186 (messages ) 191 SB 665 1141 48 (to ) 53 SB 718 1141 98 (their ) 103 SB 821 1141 237 (destinations ) 243 SB 1064 1141 48 (to ) 54 SB 1118 1141 126 (cancel ) 132 SB 1250 1141 69 (the ) 75 SB 1325 1141 159 (positive ) 165 SB 1490 1141 186 (messages ) 192 SB 1682 1141 50 (as ) 56 SB 1738 1141 149 (quickly ) 155 SB 1893 1141 50 (as ) 56 SB 1949 1141 151 (possible) 151 SB 300 1192 82 (will ) 92 SB 392 1192 141 (greatly ) 151 SB 543 1192 138 (reduce ) 148 SB 691 1192 69 (the ) 79 SB 770 1192 157 (number ) 167 SB 937 1192 48 (of ) 58 SB 995 1192 190 (rollbacks. ) 200 SB 1195 1192 11 ( ) 21 SB 1216 1192 134 (TWOS ) 145 SB 1361 1192 141 (always ) 152 SB 1513 1192 108 (gives ) 119 SB 1632 1192 165 (delivery ) 176 SB 1808 1192 154 (priority ) 165 SB 1973 1192 48 (to ) 59 SB 2032 1192 68 (any) 68 SB 300 1243 824 (negative message over any normal message.) 824 SB 32 0 0 42 42 0 0 0 41 /Palatino-Bold /font24 ANSIFont font 300 1344 764 (3.2.2.2 Memory Management Strategies) 764 SB 32 0 0 42 42 0 0 0 39 /Palatino-Roman /font27 ANSIFont font 300 1446 207 (Optimistic ) 209 SB 509 1446 190 (execution ) 192 SB 701 1446 170 (systems, ) 172 SB 873 1446 47 (in ) 49 SB 922 1446 78 (one ) 80 SB 1002 1446 113 (view, ) 116 SB 1118 1446 109 (trade ) 112 SB 1230 1446 114 (space ) 117 SB 1347 1446 65 (for ) 68 SB 1415 1446 105 (time. ) 108 SB 1523 1446 11 ( ) 14 SB 1537 1446 60 (By ) 63 SB 1600 1446 158 (keeping ) 161 SB 1761 1446 168 (multiple ) 171 SB 1932 1446 128 (copies ) 131 SB 2063 1446 37 (of) 37 SB 300 1497 93 (data ) 98 SB 398 1497 123 (items, ) 128 SB 526 1497 92 (they ) 97 SB 623 1497 75 (can ) 80 SB 703 1497 77 (run ) 82 SB 785 1497 237 (applications ) 242 SB 1027 1497 126 (faster. ) 131 SB 1158 1497 11 ( ) 16 SB 1174 1497 81 (The ) 86 SB 1260 1497 85 (cost ) 90 SB 1350 1497 41 (is ) 46 SB 1396 1497 94 (high ) 99 SB 1495 1497 168 (memory ) 174 SB 1669 1497 212 (utilization. ) 218 SB 1887 1497 11 ( ) 17 SB 1904 1497 196 (Optimistic) 196 SB 300 1548 190 (execution ) 193 SB 493 1548 159 (systems ) 162 SB 655 1548 69 (are ) 72 SB 727 1548 113 (likely ) 116 SB 843 1548 48 (to ) 51 SB 894 1548 108 (place ) 111 SB 1005 1548 32 (a ) 35 SB 1040 1548 116 (much ) 119 SB 1159 1548 131 (higher ) 134 SB 1293 1548 117 (strain ) 121 SB 1414 1548 58 (on ) 62 SB 1476 1548 168 (memory ) 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