6.2.1 Using SIDL Raw Arrays

Raw arrays (and vectors) are used as arguments in the call to mulMatVec. Note that multidimensional SIDL raw arrays are always assumed to use column-major storage. This requirement necessitates special treatment when calling methods that use SIDL raw arrays as arguments from languages that follow a default row-major array storage order (C and C++). The caller may choose to alter the memory layout of the array argument throughout its entire lifetime, or alternatively perform a matrix transpose operation on `native' arrays before and after every call to a SIDL method that uses raw arrays. In the example presented here, we have chosen to adopt column-major storage throughout the lifetime of the raw array argument A, as shown in the initialization code shown below

  /*      _        _           _   _           _   _ 
   *     | 1.0  4.0 |         | 1.0 |         | 3.0 |
   * A = | 2.0  5.0 |    v1 = | 2.0 |  sda1 = | 4.0 |
   *     | 3.0  6.0 |          -    -         | 5.0 | 
   *     -          -                         -     - 
   *
   * Note that A needs to be stored in column-major order to make
   * the call using SIDL raw arrays
   */
   value = 0.0;
   for (i = 0; i <= m; i++){
     for (j = 0; j <= n; j++){
       A[i*n+j] = (value += 1.0);
     }
   }

When making a call to a SIDL method that has SIDL raw arrays arguments, the dimensions of those arrays must be explicitly included in the argument list in the SIDL specification. No special `wrapping' of native arrays is needed to make a call using SIDL raw arrays arguments. This can be seen in the call to the mulMatVec method.

   retval = arrayop_LinearOp_mulMatVec(linopPort, alpha, A, v1, y, m , n, 
                                       &throwaway_excpt);
   if (retval != 0){
     fprintf(stderr, "Error:: %s:%d: Error in call to mulMatVec() \n",
             __FILE__, __LINE__);
      return(-1);
   }

The requirement to use column-major memory layout is one of the restrictions imposed by Babel to allow for the use of raw arrays. See the Babel User Guide for the complete list.