src/examples/matmult.c

   1 /* matmult.c
   2
   3    Test program to do matrix multiplication on large arrays.
   4
   5    Intended to stress virtual memory system.
   6
   7    Ideally, we could read the matrices off of the file system,
   8    and store the result back to the file system!
   9  */
  10
  11 #include <stdio.h>
  12 #include <syscall.h>
  13
  14 /* You should define DIM to be large enough that the arrays
  15    don't fit in physical memory.
  16
  17     Dim       Memory
  18  ------     --------
  19      16         3 kB
  20      64        48 kB
  21     128       192 kB
  22     256       768 kB
  23     512     3,072 kB
  24   1,024    12,288 kB
  25   2,048    49,152 kB
  26   4,096   196,608 kB
  27   8,192   786,432 kB
  28  16,384 3,145,728 kB */
  29 #define DIM 128
  30
  31 int A[DIM][DIM];
  32 int B[DIM][DIM];
  33 int C[DIM][DIM];
  34
  35 int
  36 main (void)
  37 {
  38   int i, j, k;
  39
  40   /* Initialize the matrices. */
  41   for (i = 0; i < DIM; i++)
  42     for (j = 0; j < DIM; j++)
  43       {
  44         A[i][j] = i;
  45         B[i][j] = j;
  46         C[i][j] = 0;
  47       }
  48
  49   /* Multiply matrices. */
  50   for (i = 0; i < DIM; i++)
  51     for (j = 0; j < DIM; j++)
  52       for (k = 0; k < DIM; k++)
  53         C[i][j] += A[i][k] * B[k][j];
  54
  55   /* Done. */
  56   exit (C[DIM - 1][DIM - 1]);
  57 }