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70 lines
1.5 KiB
70 lines
1.5 KiB
5 years ago
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#include "mpi.h"
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#include <stdio.h>
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#include <math.h>
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double f( double );
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double f( double a)
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{
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return (4.0 / (1.0 + a*a));
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}
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int main( int argc, char *argv[] )
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{
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int done = 0, n, myid, numprocs, i;
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double PI25DT = 3.141592653589793238462643;
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double mypi, pi, h, sum, x;
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double startwtime=0.0, endwtime;
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int namelen;
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char processor_name[MPI_MAX_PROCESSOR_NAME];
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MPI_Init(&argc,&argv);
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MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
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MPI_Comm_rank(MPI_COMM_WORLD,&myid);
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MPI_Get_processor_name(processor_name,&namelen);
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fprintf(stderr,"Process %d on %s\n",
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myid, processor_name);
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while (!done)
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{
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if (myid == 0)
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{
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printf("Enter the number of intervals (0 quits):\n");
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scanf("%d",&n);
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startwtime = MPI_Wtime();
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}
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MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
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if (n == 0)
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done = 1;
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else
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{
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h = 1.0 / (double) n;
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sum = 0.0;
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for (i = myid + 1; i <= n; i += numprocs)
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{
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x = h * ((double)i - 0.5);
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sum += f(x);
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}
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mypi = h * sum;
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MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
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if (myid == 0)
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{
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printf("pi is approximately %.16f, Error is %.16f\n",
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pi, fabs(pi - PI25DT));
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endwtime = MPI_Wtime();
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printf("wall clock time = %f\n",
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endwtime-startwtime);
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}
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}
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}
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MPI_Finalize();
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}
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