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44 lines
869 B
C
44 lines
869 B
C
2 years ago
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <mpi.h>
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double f( double x);
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int main( int argc, char *argv[]){
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int n, mynode, totalnodes, i;
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double PI25DT = 3.141592653589793238462643;
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double mypi, pi, h, sum, x;
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MPI_Init(&argc,&argv);
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MPI_Comm_size(MPI_COMM_WORLD,&totalnodes);
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MPI_Comm_rank(MPI_COMM_WORLD,&mynode);
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if(mynode == 0){
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if(argc != 2){
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n = 20;
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}else{
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n = atoi(argv[1]);
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}
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}
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MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
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h = 1.0 / ((double) n*totalnodes);
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sum = 0.0;
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for (i = 1+mynode*n; i <= n*(mynode+1); i++){
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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 (mynode == 0){
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printf("pi is approximately %.16f, Error is %e\n",pi, fabs(pi - PI25DT));
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}
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MPI_Finalize();
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return 0;
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}
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double f( double x )
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{
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return (4.0 / (1.0 + x*x));
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}
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