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  1. #include<stdio.h>
  2.  
  3. #define N  (2)
  4.  
  5. void mult(double *ma, double *mb, double *mc, int n)
  6. {
  7.     int i, j, k;
  8.     double sum;
  9.     for (j = 0; j < n; j++) {
  10.         for (i = 0; i < n; i++) {
  11.             sum = 0.0;
  12.             for (k = 0; k < n; k++) {
  13.                 sum += *(ma + j * n + k) * (*(mb + k * n + i));
  14.             }
  15.             *(mc + j * n + i) = sum;
  16.         }
  17.     }
  18. }
  19.  
  20. void print_matrix(double *x, char *s)
  21. {
  22.     int i, j;
  23.     printf("%s =\n", s);
  24.     for (j = 0; j < N; j++) {
  25.         printf("  | ");
  26.         for (i = 0; i < N; i++) {
  27.             printf("%f ", *(x + j * N + i));
  28.         }
  29.         printf("|\n");
  30.     }
  31. }
  32.  
  33. int main()
  34. {
  35.     double ma[N][N] = { {1.0, 2.0}, {3.0, 4.0} };
  36.     double mb[N][N] = { {1.0, 2.0}, {-2.0, -1.0} };
  37.     double mc[N][N] = { 0.0 };
  38.  
  39.     mult((double *) ma, (double *) mb, (double *) mc, N);
  40.     print_matrix((double *) ma, "ma");
  41.     print_matrix((double *) mb, "mb");
  42.     print_matrix((double *) mc, "mc = ma * mb");
  43.  
  44.     return 0;
  45. }
Success #stdin #stdout 0.01s 1720KB
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stdin
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Standard input is empty
stdout
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ma =
  | 1.000000 2.000000 |
  | 3.000000 4.000000 |
mb =
  | 1.000000 2.000000 |
  | -2.000000 -1.000000 |
mc = ma * mb =
  | -3.000000 0.000000 |
  | -5.000000 2.000000 |
https://ideone.com/ocpuNv
language:
C (gcc 8.3)
created:
11 years ago
visibility:
secret

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