text: #define alpha( i,j ) A[ (j)*lda + (i) ]
  #define  beta( i,j ) B[ (j)*ldb + (i) ]
  #define gamma( i,j ) C[ (j)*ldc + (i) ]
  
  void MyGemm(int m, int n, int k,
              double *A, int lda,
              double *B, int ldb,
              double *C, int ldc)
  {
      int i, p, j;
  
      for ( i=0 ; i<m ; i++ )
          for ( p=0 ; p<k ; p++ )
              for ( j=0 ; j<n ; j++ )
                  gamma( i,j ) += alpha( i,p ) * beta( p,j );
  }
  