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FALLSEM2021-22_CSE3049_TH_VL2021220103978_Reference_Material_I_16-Aug-2021_Parallel_Speedup_ _Parall

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8/25/2021Parallel Speedup — Parallel Computing Conceptsselkie.macalester.edu/csinparallel/modules/IntermediateIntroduction/build/html/ParallelSpeedup/ParallelSpeedup.html1/2Parallel SpeedupIntroductionThespeedupof a parallel algorithmovera corresponding sequential algorithm is the ratio of the computetime for the sequential algorithm to the time for the parallel algorithm. If the speedup factor isn, then wesay we haven-foldspeedup. For example, if a sequential algorithm requires 10 min of compute time and acorresponding parallel algorithm requires 2 min, we say that there is 5-fold speedup.The observed speedup depends on all implementation factors. For example, more processors often leadsto more speedup; also, if other programs are running on the processors at the same time as a programimplementing a parallel algorithm, those other programs may reduce the speedup. Even if a problem isembarrassingly parallel, one seldom actually obtains n-fold speedup when using n-fold processors. Thereare a couple of explanations for this occurrence:There is oftenoverheadinvolved in a computation. For example, in the solar system computation,results need to be copied across the network upon every iteration. This communication is essential tothe algorithm, yet the time spend on this communication does not directly compute more solutions to

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