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example which cannot benefit from either techniques. This loop is almost identical to theloop in Figure 2.4(a) except this loop can exit early if the computed cost exceeds a threshold.Since all the loop statements participate in a single dependence cycle (they form asingle strongly-connected component in the dependence graph), DSWP is unable to parallelizethe loop. Similarly, the dependence height of the longest cycle in the dependencegraph is equal to the dependence height of the entire loop iteration rendering DOACROSSineffective as well.To overcome the limitation caused by the conservative nature of static analysis, othertechniques are proposed to take advantage of runtime information. Among these techniques,some observe dependences at runtime and schedule loop iterations correspondingly.Synchronizations are inserted to respect a dependence between two iterations only if thatdependence manifests at runtime. Inspector-Executor (IE) [53, 60, 65] style parallelizationtechniques are representative of this category of techniques. IE consists of three phases: inspection,scheduling, and execution. A complete dependence graph is built for all iterationsduring the inspecting process. By topological sorting the dependence graph, each iterationis assigned to a wavefront number for later scheduling. At runtime, iterations with the samewavefront number can execute concurrently while iterations with larger wavefront numbershave to wait till those with smaller wavefront numbers to finish. The applicability of IE islimited by the possibility of constructing an inspector loop at compile time. This inspectorloop goes through all memory addresses being accessed in each iteration and determinesthe dependences between iterations. Since inspector loop is duplicated from the originalloop, it is required not to cause any side effect (e.g., update the shared memory). Becauseof these limitations, example loop in Figure 2.6 cannot be parallelized by IE since withoutactually updating the values of node, we won’t know whether the loop will exit.IE checks dependences at runtime before it enables any concurrent execution. Anothergroup of techniques which also take advantage of runtime information allow concurrentexecution of potentially dependent loop iterations even before they check the dependences.18
X3 X 43 4XX6 56 5Figure 2.7: PDG after breaking the loop exit control dependenceThread 1 Thread 2Thread 3Thread 4Thread 1 Thread 2Thread 3Thread 46.16.14.14.16.26.24.25.15.14.26.36.34.35.23.13.15.24.36.46.44.45.33.26.53.25.34.46.54.55.43.34.56.63.35.46.64.65.53.4(a) TLS(a) SpecDSWPFigure 2.8: TLS and SpecDSWP schedules for the loop shown in Figure 2.619
Page 1 and 2: AUTOMATICALLY EXPLOITINGCROSS-INVOC
Page 4 and 5: techniques. Among twenty programs f
Page 6 and 7: in particular. Their professionalis
Page 8 and 9: ContentsAbstract . . . . . . . . .
Page 10 and 11: 4.5.4 Load Balancing Techniques . .
Page 12 and 13: 2.4 Sequential Loop Example for DOA
Page 14 and 15: 4.5 Overview of SPECCROSS: At compi
Page 16 and 17: 1.1 Limitations of Existing Approac
Page 18 and 19: advanced forms of parallelism (MPI,
Page 20 and 21: the graph stands for an iteration i
Page 22 and 23: 1.2 ContributionsFigure 1.5 demonst
Page 24 and 25: 1.3 Dissertation OrganizationChapte
Page 26 and 27: alias the array regular via inter-p
Page 28 and 29: 1 for (i = 0; i < M; i++){2 node =
Page 30 and 31: 1 cost = 0;2 node = list->head;3 Wh
Page 34 and 35: These techniques are referred to as
Page 36 and 37: unnecessary overhead at runtime.Tab
Page 38 and 39: Chapter 3Non-Speculatively Exploiti
Page 40 and 41: for a variety of reasons. For insta
Page 42 and 43: 12x11x10xDOMOREPthread Barrier9xLoo
Page 44 and 45: Algorithm 1: Pseudo-code for schedu
Page 46 and 47: Algorithm 2: Pseudo-code for worker
Page 48 and 49: 3.3 Compiler ImplementationThe DOMO
Page 50 and 51: to T i . DOMORE’s MTCG follows th
Page 52 and 53: Outer_Preheaderbr BB1ABB1A:ind1 = P
Page 54 and 55: Algorithm 3: Pseudo-code for genera
Page 56 and 57: Scheduler Function SchedulerSync Fu
Page 58 and 59: SchedulerWorker1 Worker2Worker3Work
Page 60 and 61: 3.5 Related Work3.5.1 Cross-invocat
Page 62 and 63: ations during the inspecting proces
Page 64 and 65: for (t = 0; t < STEP; t++) {L1: for
Page 66 and 67: sequential_func() {for (t = 0; t <
Page 68 and 69: Workerthread 1Workerthread 2Workert
Page 70 and 71: library provides efficient misspecu
Page 72 and 73: Workerthread 1TimeFigure 4.6: Timin
Page 74 and 75: 4.2 SPECCROSS Runtime System4.2.1 M
Page 76 and 77: takes up to 200MB memory space.To d
Page 78 and 79: checkpoint, the child spawns new wo
Page 80 and 81: Operation DescriptionFunctions for
Page 82 and 83:
Main thread:main() {init();create_t
Page 84 and 85:
implemented in the Liberty parallel
Page 86 and 87:
Algorithm 5: Pseudo-code for SPECCR
Page 88 and 89:
CROSS, since SPECCROSS can be appli
Page 90 and 91:
techniques.Synchronization via sche
Page 92 and 93:
Source Benchmark Function % of exec
Page 94 and 95:
applied to the outermost loop, gene
Page 96 and 97:
5.2 SPECCROSS Performance Evaluatio
Page 98 and 99:
and the number of checking requests
Page 100 and 101:
8x7xno misspec.with misspec.Geomean
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This thesisPrevious workSpeedup (x)
Page 104 and 105:
Program Speedup6x5x4x3x2xLOCALWRITE
Page 106 and 107:
for DOMORE and SPECCROSS. Others (e
Page 108 and 109:
programs and it achieves a geomean
Page 110 and 111:
Bibliography[1] R. Allen and K. Ken
Page 112 and 113:
[15] R. Cytron. DOACROSS: Beyond ve
Page 114 and 115:
[31] T. B. Jablin, Y. Zhang, J. A.
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[47] A. Nicolau, G. Li, A. V. Veide
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[62] L. Rauchwerger and D. Padua. T
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national conference on Parallel Arc
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