Hello, I'm trying to make a program that will multiply 2 matrices using shmget() and fork(). For example, I would need to multiply a 64 x 64 matrix using 4 processes or 16 processes, and the multi-processes will be created using fork. Each process will calculate a partition of the final Matrix
Now, I'm not sure whether I should write all the matrices to the shared memory or just a single integer to keep track of what partition to calculate. I'm also not sure if I'm using fork correctly, as my print commands print out twice each instead of once.
#include <stdio.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#define DIM 4
#define NUM_OF_FORK_CALLS 2
#define NUM_OF_PROC 4
int main()
{
pid_t pid;
int segment_id;
int *partition;
*partition = 0;
int i;
int j;
int matrixA[DIM][DIM];
int matrixB[DIM][DIM];
int matrixC[DIM][DIM];
//allocating a shared memory segment
segment_id = shmget(IPC_PRIVATE, sizeof(int)*(DIM*DIM)*3, IPC_CREAT|0666);
//attach the shared memory segment to the partition variable
partition = (int *) shmat(segment_id, NULL,0);
//fill the matrices
for(i = 0; i < DIM; i++)
{
for(j = 0; j < DIM; j++)
{
matrixA[i][j] = i + j;
matrixB[i][j] = i + 3;
}
}
for(i = 0; i < NUM_OF_FORK_CALLS; i++)
{
pid = fork();
}
//error occurred
if(pid < 0)
{
fprintf(stderr, "Fork Failed");
return 1;
}
//child process
else if(pid==0)
{
int start = (*partition * DIM)/NUM_OF_PROC;
/*The start position will tell which row to start calculating */
int end = ((*partition+1) * DIM)/NUM_OF_PROC;
/*The end position wil tell which row to stop calculating*/
int i;
int j;
int k;
//These for loops will calculate a partition of C
for(i = start; i<end; i++)
{
for(j = 0; j < DIM; j++)
{
matrixC[i][j] = 0;
for(k = 0; k < DIM; k++)
{
matrixC[i][j] += matrixA[i][k] * matrixB[k][j];
}
}
}
}
//parent process
else
{
wait(NULL);
int i;
int j;
//print matrix A
for(i = 0; i < DIM; i++)
{
for(j = 0; j<DIM; j++)
{
printf("%d ",matrixA[i][j]);
}
printf("\n");
}
printf("-----------\n\n");
//print matrix B
for(i = 0; i < DIM; i++)
{
for(j = 0; j<DIM; j++)
{
printf("%d ",matrixB[i][j]);
}
printf("\n");
}
printf("-----------\n\n");
//print matrix C
for(i = 0; i < DIM; i++)
{
for(j = 0; j<DIM; j++)
{
printf("%d ",matrixC[i][j]);
}
printf("\n");
}
printf("-----------\n\n");
}
return 0;
}Any help would be appreciated, thanks in advance