Zero Suppression with OpenMP
CS 462 Parallel Programming, Project #2
Dr. Beck
Zerosuppressionisaformofcompressionthattakesasinputanarrayofintegers
andreplaceseverysequenceofzeroswithtwointegers:
a. asinglezero,followedby
b. thenumberofconsecutivezerosinthesequence.
Forexample,thesequence
5,0,0,0,0,3,2,0,4,1,5,0,0,0,6
wouldbecompressedas
5,0,4,3,2,0,1,4,1,5,0,3,6
YouaretowriteaparallelOpenMPprogramtoreadinanNxNtwodimensional
arrayfromafile(Nspecifiedasacommandlineparameter)inrowmajororder,and
either
1. Compressthematrixinrowmajororder,or
A[0,0],A[0,1],A[0,2],…A[0,N-1],A[1,0],A[1,1],A[1,2],…A[1,N-1],…
2. Compressthematrixincolumnmajororder.
A[0,0],A[1,0],A[2,0],…A[N-1,0],A[0,1],A[1,1],A[2,1],…A[N-1,1],…
Acommand-lineargumentshouldbeusedtodeterminethedirectionofsuppression
• -drforzerosuppressioninrowmajororder
• -dcforzerosuppressionincolumnmajororder
Iftheargumentisnotpresent,thenyourprogramshoulduseuniformrandom
samplingtodeterminethemostefficientdirection(choosearandomsetofstarting
pointsanddirectionsandfindtheaveragelengthofazerosequenceineach
direction).
Theoutputshouldstartwithavaluethatspecifieswhichdirectionofcompression
wasused(1forrowmajor,2,forcolumnmajor).
Youshouldwriteaprogram(notnecessarilyparallel)tocheckyourresults,and
obtaintimings(bothwithandwithoutI/O)forfilesandnumbersofthreadsupto
thecapacityofthelargestmulticorenodesintheNewtonclusters.
Whatchangetothisspecificationwouldmakecheckingmoreeasilyparallelizable?
GeneratingInputFiles
Theeasiestwaytogenerateaninputfileistocreateanarraywithallthedifferent
possibleinputsoccurringwiththerelativefrequencythatyouwantinthefile.Thus
ifthefilewastocontainintegersintherange[0..9]withequalfrequencyexceptthat
9occurswithtwicethefrequencyoftheothernumbers,thenyouwouldusean
arraywith11entries,witheachofthenumbersintherange[0..8]occurringonce
andthenumber9occuringtwice.Thenyouwouldgenerateaninputfileofanysize
usingauniformdistributionrandomnumbergenerator(suchasrand()fromtheC
library)modifiedtoproduceindicesintherange[0..10]andthenusingthose
indicestoindexintothearray.
Forthisproject,youwanttoensurethattherearerunsofzerostobecompressed,
sotheabovetechniquecanbeusedwithamodification.Negativenumberscanbe
usedtorepresentrunsofzeros(-2represents2zeros,-3represents3zeros,etc).If
thesespecialvaluesareaddedtothevaluesinthearray,thenwhentheycomeup
thentheappropriatenumberofzeroscanbegenerated.Thisrequiresthatallofthe
othervaluesinthearraybenon-negative,whichisacceptable.Then,aswith
numbers,thefrequencyofrunsofzerosofdifferentlengthscanbeadjustedby
adjustingthefrequencyofthevariousnegativenumbersinthearray.