HPC RIVR
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Milovan Tomašević works as a researcher at the Faculty of Information Studies in Novo Mesto within the project “SUPERVISION OF NATIONAL RESEARCH INFRASTRUCTURES - HPC RIVR”, the Ministry of Education, Science and Sport, Slovenia, for the period 2018-2020th years.
Faculty of Information Studies in Novo Mesto
OpenMP is the dominant shared-memory programming model in computational science.
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#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
int main (int argc, char *argv[])
{
//initialize variables
int i;
double pi = 0;
int niter = 100000000;
// Get timing
double start,end;
start=omp_get_wtime();
// Calculate PI using Leibnitz sum
/* Fork a team of threads */
#pragma omp parallel for reduction(+ : pi)
for(i = 0; i < niter; i++)
{
pi = pi + pow(-1, i) * (4 / (2*((double) i)+1));
} /* Reduction operation is done. All threads join master thread and disband */
// Stop timing
end=omp_get_wtime();
// Print result
printf("Pi estimate: %.20f, obtained in %f seconds\n", pi, end-start);
}
C Examples of Parallel Programming with OpenMP (Open Multi-Processing)
The Message Passing Interface (MPI) is a library specification that allows HPC to pass information between its various nodes and clusters. HPC uses OpenMPI, an open-source, portable implementation of the MPI standard. OpenMPI contains a complete implementation of version 1.2 of the MPI standard and also MPI-2.
OpenMPI is both a runtime and compile-time environment for MPI-compliant code.
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#include <mpi.h>
#include <stdio.h>
int main(int argc, char* argv[])
{
MPI_Init(&argc,&argv);
// Get local rank
int myRank;
MPI_Comm_rank(MPI_COMM_WORLD, &myRank);
// Timing
double timeStart;
double timeEnd;
timeStart = MPI_Wtime();
// Repeated send/receive several times for accurate timing
int i;
int niter=1000;
for(i = 0; i < niter; i++)
{
if(myRank == 0) // Work for process with rank 0
{
MPI_Status status;
MPI_Request request;
char ping[5] = "ping";
char pongReceive[5];
MPI_Isend(ping, 5, MPI_CHAR, 1, 17, MPI_COMM_WORLD, &request);
MPI_Recv(pongReceive, 5, MPI_CHAR, 1, 23, MPI_COMM_WORLD, &status);
MPI_Wait(&request, &status);
}
else if(myRank == 1) // Work for process with rank 1
{
MPI_Status status;
MPI_Request request;
char pong[5] = "pong";
char pingReceive[5];
MPI_Isend(pong, 5, MPI_CHAR, 0, 23, MPI_COMM_WORLD, &request);
MPI_Recv(pingReceive, 5, MPI_CHAR, 0, 17, MPI_COMM_WORLD, &status);
MPI_Wait(&request, &status);
}
else
{
}
}
// Timing
timeEnd = MPI_Wtime();
printf("Commucation time was %10.7f microseconds\n", ((timeEnd-timeStart)/(niter*2))*1000000);
MPI_Finalize();
}
Message Passing Interface (MPI) - C Examples
