Back to: 23. Multi Core Programming and Threads
// testingProgram.cpp // compile with // c++ testingProgram.cpp -o myTest -std=c++11 -pthread // execute with // ./myTest #include<iostream> #include <thread> #include<chrono> class SimpleTimer{ private: int64_t timerStart; int64_t timerEnd; int64_t timerInProgress; public: SimpleTimer(const int64_t & =0); void start(); void end(); double getTime(); }; SimpleTimer::SimpleTimer(const int64_t & _inProgress){ timerInProgress=_inProgress; if(timerInProgress==1){ timerStart=std::chrono::high_resolution_clock::now().time_since_epoch().count(); } } void SimpleTimer::start(){ timerInProgress=1; timerStart=std::chrono::high_resolution_clock::now().time_since_epoch().count(); } void SimpleTimer::end(){ timerInProgress=2; timerEnd=std::chrono::high_resolution_clock::now().time_since_epoch().count(); } double SimpleTimer::getTime(){ if(timerInProgress!=2){ return -1.0; } double fR= double(timerEnd)-double(timerStart); fR/= 1000000000.0; return fR; } long powerFunction(long a, long b, long p){ long res=1; long i=0; while(i < b){ res*=a; res%=p; ++i; } return res; } void executeOnOneThread(long* alpha, long* beta, long* gamma, long p, long m, long start, long end){ while(start<end){ gamma[start]=powerFunction(alpha[start],beta[start],p); start+=m; } } void nonParallelFunction(long* alpha, long* beta, long* gamma, long p, long n){ long i=0; while(i < n){ gamma[i]=powerFunction(alpha[i],beta[i],p); ++i; } } void parallelFunction(long* alpha, long* beta, long* gamma, long p, long n, long m){ if(m<1){m=1;} std::thread* allTh; allTh=new std::thread[m]; for(long i=0;i<m;++i){ allTh[i]=std::thread(executeOnOneThread,alpha,beta,gamma,p,m,i,n); } for(long i=0;i<m;++i){ allTh[i].join(); } delete[] allTh; } int main(){ long m=std::thread::hardware_concurrency(); std::cout<<"Number of threads\t"<<m<<".\n"; std::cout<<"Starting execution ...\n"; long *alpha, *beta, *gammaN, *gammaP; long p=17; long N=100000; alpha=new long[N]; beta=new long[N]; gammaN=new long[N]; gammaP=new long[N]; alpha[0]=8;beta[0]=5183;alpha[1]=9;beta[1]=4351; alpha[2]=7;beta[2]=4711; long i=3; while(i < N){ alpha[i]=alpha[i-3];beta[i]=beta[i-3];++i; } SimpleTimer tm; tm.start(); nonParallelFunction(alpha,beta,gammaN,p,N); tm.end(); std::cout<<"Running times:\n"; std::cout <<"Non-parallel\t\t" << tm.getTime() << "\n"; tm.start(); parallelFunction(alpha,beta,gammaP,p,N,m); tm.end(); std::cout <<"Parallel\t\t" << tm.getTime() << "\n"; delete[] alpha;delete[] beta;delete[] gammaN;delete[] gammaP; return 0; }