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- /*!
- \file matmul.c
- \brief Matrix multiplication implementation.
-
- \author Nikos Pitsianis
- \author Dimitris Floros
- \author Christos Choutouridis 8997 <cchoutou@ece.auth.gr>
- \date 2020-05-05
- */
-
- #include <stdio.h>
- #include <stdlib.h>
- #include <math.h>
- #include <sys/time.h>
- #include <assert.h>
-
- #define MAX_ITER 10
- #define sub2ind(i,j,n) (j) + (i)*(n)
-
- /*!
- * Square Matrix multiplication
- * \param C pointer to output matrix
- * \param A pointer to input matrix A
- * \param B pointer to input matrix B
- * \param n Size of matrices (both sizes)
- * \return none
- *
- * \note
- * This version executes row major order ijk
- */
- void matrixMult(float * const C, float const * const A, float const * const B, int const n) {
-
- for (int i = 0; i < n; i++) { /* rows */
- for (int j = 0; j < n; j++) { /* cols */
- C[ sub2ind(i,j,n) ] = 0; /* initialize output value */
- for (int k = 0; k < n; k++) { /* accumulate products */
- C[ sub2ind(i,j,n) ] +=
- A[ sub2ind(i,k,n) ] * B[ sub2ind(k,j,n) ];
- }
- }
- }
-
- }
-
- /*!
- * Initialize matrix with random indices and return the matrix pointer.
- *
- * \param n The size of the matrix (both of them)
- * \return Pointer to allocated and initialized matrix
- */
- float * matrixInit(int const n) {
-
- float *M = (float *) malloc( n*n*sizeof(float) );
-
- for (int i = 0; i < n; i++) /* rows */
- for (int j = 0; j < n; j++) /* cols */
- M[ sub2ind(i,j,n) ] = (float)rand()/(float)(RAND_MAX);
-
- return M;
- }
-
- int cmpfunc (const void * a, const void * b) {
- double v =*(double*)a - *(double*)b;
- return (v < 0) ? -1 : (v > 0) ? 1 : 0;
- }
-
- /*!
- * A unit testing like main function to profile our code
- */
- int main(int argc, char **argv)
- {
-
- struct timeval start, end; /* time structs */
- double time[MAX_ITER] = {0.0}; /* execution time array in ms */
- float *A, *B, *C; /* matrix declarations */
- int n; /* matrix size */
-
- /* read matrix size (or use default) */
- if (argc != 2){
- fprintf( stderr, "Usage:\n %s n\n where n is the matrix size.\n",
- argv[0]);
- exit(1);
- }
- n = atoi( argv[1] );
-
- /* initialize matrices */
- A = matrixInit( n );
- B = matrixInit( n );
- C = (float *) malloc( n*n*sizeof(float) );
-
- /* compute matrix multiplication */
- for (int it = 0; it < MAX_ITER; it++) {
- gettimeofday(&start, NULL);
- matrixMult( C, A, B, n );
- gettimeofday(&end, NULL);
-
- time[it] = (end.tv_sec - start.tv_sec) * 1000.0 + /* sec to ms */
- (end.tv_usec - start.tv_usec) / 1000.0; /* us to ms */
-
- printf("Iter: %d Time: %f ms\n", it, time[it]);
- }
-
- /* we need to use the result -- verify it */
- for (int i = 0; i < n; i++) { /* rows */
- for (int j = 0; j < n; j++) { /* cols */
-
- float gold = 0;
-
- for (int k = 0; k < n; k++) { /* accumulate products */
- gold += A[ sub2ind(i,k,n) ] * B[ sub2ind(k,j,n) ];
- }
-
- assert( (gold - C[sub2ind(i,j,n)]) < 1e-3 );
-
- }
- }
-
- // median calculation
- qsort ((void*)time, MAX_ITER, sizeof(time[0]), cmpfunc);
- printf("Median: %f [msec]\n", (MAX_ITER % 2) ?
- time[MAX_ITER/2] :
- (time[MAX_ITER/2] + time[MAX_ITER/2 -1]) /2
- );
- }
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