pthreads/matrixmul.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <pthread.h>
   4
   5 struct matrix {
   6    unsigned int rows;
   7    unsigned int cols;
   8    int **data;
   9 };
  10
  11 struct matrix_index {
  12    unsigned int row;
  13    unsigned int col;
  14 };
  15
  16 struct matrix *mat1 = NULL;
  17 struct matrix *mat2 = NULL;
  18 struct matrix *mat3 = NULL;
  19
  20 /* function prototypes */
  21 void allocmat(struct matrix **mat, int rows, int cols);
  22 void freemat(struct matrix **mat);
  23 void readmat(const char *path, struct matrix **mat);
  24 void printmat(const struct matrix *mat);
  25 void *mulvect(void *arg);
  26
  27 int main(int argc, char *argv[]) {
  28    pthread_t *tid;
  29    struct matrix_index *v;
  30    unsigned int i, j, k, numthreads;
  31
  32    /* arguments validations */
  33    if (argc != 3) {
  34       fprintf(stderr, "Incorrect num of args.\nUsage: ./matrixmul matfile1 matfile2\n");
  35       exit(EXIT_FAILURE);
  36    }
  37
  38    /* read matrix data from files */
  39    readmat(argv[1], &mat1);
  40    readmat(argv[2], &mat2);
  41
  42    /* Is the multiplication feasible by definition? */
  43    if (mat1->cols != mat2->rows) {
  44       fprintf(stderr, "Matrices' dimensions size must satisfy (NxM)(MxK)=(NxK)\n");
  45       exit(EXIT_FAILURE);
  46    }
  47
  48    /* allocate memory for the result */
  49    allocmat(&mat3, mat1->rows, mat2->cols);
  50
  51    /* How many threads do we need ?*/
  52    numthreads = mat1->rows * mat2->cols;
  53
  54    /* v[k] holds the (i, j) pair in the k-th computation */
  55    v = malloc(numthreads * sizeof(struct matrix_index));
  56
  57    /* allocate memory for the threads' ids */
  58    tid = malloc(numthreads * sizeof(pthread_t));
  59    if (!tid) {
  60       fprintf(stderr, "Error allocating memory\n");
  61       exit(EXIT_FAILURE);
  62    }
  63
  64    /* create the threads */
  65    for (i=0; i<mat1->rows; i++) {
  66       for (j=0; j<mat2->cols; j++) {
  67          k = i*mat1->rows + j;
  68          v[k].row = i;
  69          v[k].col = j;
  70          if (pthread_create(&tid[k], NULL, mulvect, (void *)&v[k])) {
  71             fprintf(stderr, "pthtrad_create() error\n");
  72             exit(EXIT_FAILURE);
  73          }
  74       }
  75    }
  76
  77    /* make sure all threads are done  */
  78    for (i=0; i<numthreads; i++)
  79       if (pthread_join(tid[i], NULL)) {
  80          fprintf(stderr, "pthread_join() error\n");
  81          exit(EXIT_FAILURE);
  82       }
  83
  84    /* print the result */
  85    printmat(mat3);
  86
  87    /* free matrices */
  88    freemat(&mat1);
  89    freemat(&mat2);
  90    freemat(&mat3);
  91
  92    return EXIT_SUCCESS;
  93 }
  94
  95 void allocmat(struct matrix **mat, int rows, int cols) {
  96    int i;
  97
  98    *mat = malloc(sizeof(struct matrix));
  99    if (!*mat) {
 100       fprintf(stderr, "Error allocating memory\n");
 101       exit(EXIT_FAILURE);
 102    }
 103
 104    (*mat)->rows = rows;
 105    (*mat)->cols = cols;
 106
 107    (*mat)->data = malloc(rows * sizeof(int *));
 108    if (!(*mat)->data) {
 109       fprintf(stderr, "Error allocating memory\n");
 110       exit(EXIT_FAILURE);
 111    }
 112
 113    for (i=0; i<rows; i++) {
 114       (*mat)->data[i] = malloc(cols * sizeof(int));
 115       if (!(*mat)->data[i]) {
 116          fprintf(stderr, "Error allocating memory\n");
 117          exit(EXIT_FAILURE);
 118       }
 119    }
 120 }
 121
 122 void freemat(struct matrix **mat) {
 123    unsigned int i;
 124
 125    for (i=0; i<(*mat)->rows; i++) {
 126       free((*mat)->data[i]);
 127    }
 128    free(*mat);
 129    *mat = NULL;
 130 }
 131
 132 void readmat(const char *path, struct matrix **mat) {
 133    FILE *fp;
 134    unsigned int i, j, rows, cols;
 135
 136    /* open file */
 137    if (!(fp = fopen(path, "r"))) {
 138       fprintf(stderr, "Error opening file: %s\n", path);
 139       exit(EXIT_FAILURE);
 140    }
 141
 142    /* read matrix dimensions */
 143    fscanf(fp, "%u%u", &rows, &cols);
 144
 145    /* allocate memory for matrix */
 146    allocmat(mat, rows, cols);
 147
 148    /* read matrix elements */
 149    for (i=0; i<(*mat)->rows; i++) {
 150       for (j=0; j<(*mat)->cols; j++) {
 151          fscanf(fp, "%d", &(*mat)->data[i][j]);
 152       }
 153    }
 154
 155    /* close file */
 156    fclose(fp);
 157 }
 158
 159
 160 void printmat(const struct matrix *mat) {
 161    unsigned int i, j;
 162
 163    for (i=0; i<mat->rows; i++) {
 164       for (j=0; j<mat->cols; j++) {
 165          printf("%d ", mat->data[i][j]);
 166       }
 167       printf("\n");
 168    }
 169 }
 170
 171
 172 void *mulvect(void *arg) {
 173    unsigned int i, row, col;
 174
 175    row = *((int *)arg + 0);
 176    col = *((int *)arg + 1);
 177
 178    mat3->data[row][col] = 0;
 179    for (i=0; i<mat1->cols; i++)
 180       mat3->data[row][col] += mat1->data[row][i] * mat2->data[i][col];
 181
 182    pthread_exit(NULL);
 183 }