Difference between revisions of "CSC352 Homework 4 Solutions"
| Line 484: | Line 484: | ||
=Problem 3= | =Problem 3= | ||
| + | <br /> | ||
| + | A good program by Danae for the MPI question. Note the use of '''perworker''' and '''permanager''' to make sure the total number of samples adds up ''exactly'' to '''numsamples'''. Nice touch. | ||
<br /> | <br /> | ||
<source lang="C"> | <source lang="C"> | ||
| + | [352a@beowulf 352a-aa]$ cat mpiMonteCarlo4.c | ||
| + | /* mpiMonteCarlo4.c | ||
| + | // danae | ||
| + | // | ||
| + | // Computes Pi using the Monte Carlo method with MPI, | ||
| + | // NP (user-specified) processes, and N random samples. | ||
| + | // Note that N should be evenly divisible by NP in order | ||
| + | // to truly calculate N samples. | ||
| + | // | ||
| + | // To compile and run: | ||
| + | // mpicc -o mpiMonteCarlo4 mpiMonteCarlo4.c | ||
| + | // mpirun -np [NP] ./mpiMonteCarlo [N] | ||
| + | // | ||
| + | */ | ||
| + | |||
| + | #include "mpi.h" | ||
| + | #include <stdio.h> | ||
| + | #include <stdlib.h> | ||
| + | |||
| + | #define MANAGER 0 | ||
| + | |||
| + | //-------------------------------------------------------------------- | ||
| + | // P R O T O T Y P E S | ||
| + | //-------------------------------------------------------------------- | ||
| + | void doManager(int,int); | ||
| + | void doWorker(); | ||
| + | |||
| + | //-------------------------------------------------------------------- | ||
| + | // M A I N | ||
| + | //-------------------------------------------------------------------- | ||
| + | int main(int argc, char *argv[]) { | ||
| + | int myId, noProcs, nameLen; | ||
| + | char procName[MPI_MAX_PROCESSOR_NAME]; | ||
| + | int numsamples; | ||
| + | |||
| + | if ( argc<2 ) { | ||
| + | printf( "Please Use Correct Syntax: mpirun -np [NP] ./pi2 [N]\n" ); | ||
| + | return 1; | ||
| + | } | ||
| + | |||
| + | // get the number of samples to generate | ||
| + | numsamples = atoi(argv[1]); | ||
| + | |||
| + | //--- start MPI --- | ||
| + | MPI_Init(&argc, &argv); | ||
| + | MPI_Comm_rank(MPI_COMM_WORLD, &myId); | ||
| + | MPI_Comm_size(MPI_COMM_WORLD, &noProcs); | ||
| + | MPI_Get_processor_name(procName, &nameLen); | ||
| + | |||
| + | //--- display which process we are on --- | ||
| + | printf( "Process %d of %d started.\n", myId, noProcs); | ||
| + | |||
| + | //--- farm out the work: 1 manager, several workers --- | ||
| + | if ( myId == MANAGER ) | ||
| + | doManager(noProcs, numsamples); | ||
| + | else | ||
| + | doWorker(); | ||
| + | |||
| + | //--- close up MPI --- | ||
| + | MPI_Finalize(); | ||
| + | |||
| + | return 0; | ||
| + | } | ||
| + | |||
| + | //-------------------------------------------------------------------- | ||
| + | // The manager's main work function | ||
| + | //-------------------------------------------------------------------- | ||
| + | void doManager(int noProcs, int numsamples ) { | ||
| + | double incircle = 0; | ||
| + | double workersum; | ||
| + | int i; | ||
| + | MPI_Status status; | ||
| + | |||
| + | int perworker = (1.0)*numsamples/noProcs; | ||
| + | int permanager = numsamples - perworker*noProcs; //manager picks up slack | ||
| + | |||
| + | // printf("perworker: %d\n", perworker); | ||
| + | //--- first to all workers --- | ||
| + | for(i=1; i<noProcs; i++) { | ||
| + | MPI_Send( &perworker, 1, MPI_INT, i, 0, MPI_COMM_WORLD ); | ||
| + | } | ||
| + | |||
| + | //calculate manager portion | ||
| + | srand(time(NULL)); //seed the random number generator with time | ||
| + | float x, y; | ||
| + | for(i=0; i<permanager+perworker; i++) { | ||
| + | x = 1 - (((float)rand()/(float)(RAND_MAX)) * 2.0); //random float [-1,1] | ||
| + | y = 1 - (((float)rand()/(float)(RAND_MAX)) * 2.0); //random float [-1,1] | ||
| + | if ((float)x*x + (float)y*y <= (float)(1.0)) { | ||
| + | incircle += 1; | ||
| + | } | ||
| + | } | ||
| + | |||
| + | //--- wait for worker sums --- | ||
| + | for(i=1; i<noProcs; i++) { | ||
| + | MPI_Recv( &workersum, 1, MPI_DOUBLE, MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, &status ); | ||
| + | incircle += workersum; | ||
| + | } | ||
| + | |||
| + | //--- output result --- | ||
| + | printf( "%d iterations: Pi = %f\n", permanager + noProcs*perworker, 4.0*(incircle)/(noProcs*perworker)); | ||
| + | } | ||
| + | |||
| + | //-------------------------------------------------------------------- | ||
| + | // The worker's main work function | ||
| + | //-------------------------------------------------------------------- | ||
| + | void doWorker( ) { | ||
| + | int numthrows, i; | ||
| + | |||
| + | //--- get n from manager --- | ||
| + | MPI_Status status; | ||
| + | MPI_Recv( &numthrows, 1, MPI_INT, MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, &status ); | ||
| + | |||
| + | //--- do portion of the work --- | ||
| + | double incircle = 0; | ||
| + | float x, y; | ||
| + | for (i=0; i<numthrows; i++) { | ||
| + | // generate random x, y as float [0,2], subtracts 1 to be in range [-1,1] | ||
| + | x = 1 - (((float)rand()/(float)(RAND_MAX)) * 2.0); //random float [-1,1] | ||
| + | y = 1 - (((float)rand()/(float)(RAND_MAX)) * 2.0); //random float [-1,1] | ||
| + | if ((float)x*x + (float)y*y <= (float)(1.0)) | ||
| + | incircle += 1; | ||
| + | } | ||
| + | |||
| + | //-- send result to manager --- | ||
| + | MPI_Send( &incircle, 1, MPI_DOUBLE, MANAGER, 0, MPI_COMM_WORLD ); | ||
| + | } | ||
| + | |||
</source> | </source> | ||
Latest revision as of 15:46, 8 November 2013
--D. Thiebaut (talk) 14:41, 8 November 2013 (EST)
