111 lines
2.7 KiB
C
111 lines
2.7 KiB
C
/*!
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\file matmul.c
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\brief Matrix multiplication implementation.
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\author Nikos Pitsianis
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\author Dimitris Floros
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\date 2020-05-05
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*/
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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 <sys/time.h>
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#include <assert.h>
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#define MAX_ITER 10
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#define sub2ind(i,j,n) (j) + (i)*(n)
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/*
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* matrixMult - Matrix multiplication
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*/
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void matrixMult(float * const C, /* output matrix */
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float const * const A, /* first matrix */
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float const * const B, /* second matrix */
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int const n) { /* number of rows/cols */
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for (int i = 0; i < n; i++) { /* rows */
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for (int j = 0; j < n; j++) { /* cols */
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/* initialize output value */
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C[ sub2ind(i,j,n) ] = 0;
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for (int k = 0; k < n; k++) { /* accumulate products */
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C[ sub2ind(i,j,n) ] +=
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A[ sub2ind(i,k,n) ] * B[ sub2ind(k,j,n) ];
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}
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}
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}
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} // end function 'matrixMult'
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/*
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* matrixInitAdd:
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* Initialize matrix with random indices and return the matrix
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* pointer.
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*
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*/
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float * matrixInit(int const n) {
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float *M = (float *) malloc( n*n*sizeof(float) );
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for (int i = 0; i < n; i++) /* rows */
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for (int j = 0; j < n; j++) /* cols */
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M[ sub2ind(i,j,n) ] = (float)rand()/(float)(RAND_MAX);
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return M;
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} // end function 'matrixInitAdd'
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int main(int argc, char **argv)
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{
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struct timeval start, end; /* time structs */
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double time = 0.0; /* execution time in ms */
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float *A, *B, *C; /* matrix declarations */
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int n; /* matrix size */
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/* read matrix size (or use default) */
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if (argc != 2){
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fprintf( stderr, "Uasge:\n %s n\n where n is the matrix size.\n",
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argv[0]);
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exit(1);
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}
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n = atoi( argv[1] );
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/* initialize matrices */
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A = matrixInit( n );
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B = matrixInit( n );
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C = (float *) malloc( n*n*sizeof(float) );
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/* compute matrix multiplication */
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for (int it = 0; it < MAX_ITER; it++) {
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gettimeofday(&start, NULL);
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matrixMult( C, A, B, n );
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gettimeofday(&end, NULL);
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time = ( (end.tv_sec - start.tv_sec) * 1000.0 + /* sec to ms */
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(end.tv_usec - start.tv_usec) / 1000.0 ); /* us to ms */
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printf("Iter: %d Time: %f ms\n", it, time);
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}
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/* we noeed to use the result -- verify it */
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for (int i = 0; i < n; i++) { /* rows */
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for (int j = 0; j < n; j++) { /* cols */
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float gold = 0;
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for (int k = 0; k < n; k++) { /* accumulate products */
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gold += A[ sub2ind(i,k,n) ] * B[ sub2ind(k,j,n) ];
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}
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assert( (gold - C[sub2ind(i,j,n)]) < 1e-3 );
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}
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}
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}
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