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VEC_$DPOSTMULTN                   Domain/OS                    VEC_$DPOSTMULTN


NAME
     vec_$dpostmultn - multiply a double-precision vector by a matrix

SYNOPSIS (C)
     #include <apollo/base.h>
     #include <apollo/vec.h>

     void vec_$dpostmultn(
          double *matrix,
          double *start_vec,
          long int &m,
          long int &n,
          double *result_vec)

SYNOPSIS (Pascal)
     %include '/sys/ins/base.ins.pas';
     %include '/sys/ins/vec.ins.pas';

     procedure vec_$dpostmultn(
          in matrix: univ vec_$double_matrix;
          in start_vec: univ vec_$double_vector;
          in m: integer32;
          in n: integer32;
          out result_vec: univ vec_$double_vector);

SYNOPSIS (FORTRAN)
     %include '/sys/ins/base.ins.ftn'
     %include '/sys/ins/vec.ins.ftn'

           integer*4 m, n
           parameter (m = 3, n = 4)

           double precision matrix(m, n), start_vec(n), result_vec(m)

           call vec_$dpostmultn(matrix, start_vec, m, n, result_vec)

DESCRIPTION
     Vec_$dpostmultn multiplies the n-element vector start_vec by the variably
     dimenstioned matrix matrix, and supplies the resulting m-element vector
     in result_vec.

     In C, vec_$dpostmultn applies the nxm matrix matrix as a right transform
     to the m-element row vector start_vec, and supplies the transformed n-
     element result in result_vec:

          for (i = 0; i < m; ++i) {
               result_vec[i] = 0.0;
               for (j = 0; j < n; ++j)
                    result_vec[i] += start_vec[j]
                                  * matrix[j][i];
          }

     In Pascal, vec_$dpostmultn applies the nxm matrix matrix as a right
     transform to the m-element row vector start_vec, and supplies the
     transformed n-element result in result_vec:

          for i := 1 to m do
               begin
               result_vec[i] := 0.0;
               for j := 1 to n do
                    result_vec[i] := result_vec[i]
                                  + start_vec[j]
                                  * matrix[j,i];
               end;

     In FORTRAN, vec_$dpostmultn applies the mxn matrix matrix as a left
     transform to the m-element column vector start_vec, and supplies the
     transformed n-element result in result_vec:

           do 10 i = 1, m
               result_vec(i) = 0.0
               do 10 j = 1, n
                    result_vec(i) = result_vec(i)
          &                       + start_vec(j)
          &                       * matrix(i,j)
       10  continue

     matrix
          A matrix to multiply start_vec by.

     start_vec
          An n-element vector to multiply by matrix.

     m    The number of elements in start_vec.

     n    The number of elements in result_vec.

     result_vec
          An m-element vector that is the product of matrix and start_vec.

NOTES
     Vec_$dpremultn transforms double-precision vectors from the other side.

SEE ALSO
     vec_$ipostmultn, vec_$ipostmultn16, vec_$postmultn.