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#528896
/* Author: Cyle Riggs 3mail: cyle !!at!! riggs family web %d0t% net*/#include <iostream>#include <iomanip>#include <cstdlib>#include <cmath>#include <map>#include <vector>#include "mpi.h"#define TAG_POINTS 11#define TAG_INCIRCLE 12#define REALPI 3.14159265358979323846264338327950288419716939937510using namespace std;struct CPoint { double x; double y;};double drand( double low, double high );int main( int argc, char* argv[] ) { MPI_Status status; MPI_Init( &argc, &argv ); int size = -1; int rank = -1; MPI_Comm_size( MPI_COMM_WORLD, &size ); MPI_Comm_rank( MPI_COMM_WORLD, &rank ); srand( (rank+1) * time(NULL) + clock() ); unsigned long int count = 0; if( rank == 0 ) { cout << "This program will make random points and use them to determine pi, the greater the number of points, the better the accuracy" << endl << endl; cout << "# of points? " << flush; cin >> count; } MPI_Bcast( &count, 1, MPI_INT, 0, MPI_COMM_WORLD ); //If the user chose 0 quit here if( count == 0 ) { MPI_Finalize(); return 0; } vector<CPoint> results; map<unsigned long int,unsigned long int> job_map; for( unsigned long int i = 0; i < count; i++ ) { job_map[i%size]++; } if( rank == 0 ) { cout << "Generating ~" << job_map[rank] << " random points per process" << endl; } vector<CPoint> mypoints; for( unsigned long int i = 0; i < job_map[rank]; i++ ) { CPoint p; p.x = drand( -1.0, 1.0 ); //Generate X for the point p.y = drand( -1.0, 1.0 ); //Generate Y for the point mypoints.push_back( p ); } double my_in_circle = 0.0; for( vector<CPoint>::iterator point = mypoints.begin(); point != mypoints.end(); point++ ) { if( (pow(point->x,2)+pow(point->y,2)) < 1 ) { my_in_circle++; } } double final_in_circle = 0.0; //Add together everybody's count of points in the circle MPI_Reduce( &my_in_circle, &final_in_circle, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD ); if( rank == 0 ) { double est_pi = (4.0 * (final_in_circle/count)); double accuracy = est_pi - REALPI; //PI is the 4 * (# of points that fell in circle / the total number of points) cout << endl << endl; cout << "Pi: " << est_pi << endl; cout << "Accuracy: " << accuracy << endl; } MPI_Finalize(); return 0;}double drand( double low, double high ) { double retval = static_cast<double>( rand() ) / RAND_MAX; return low + ((high - low) * retval);}