VEC_$IPREMULT16                   Domain/OS                    VEC_$IPREMULT16


NAME
     vec_$ipremult16 - multiply a 16-bit vector by a 4x4 matrix

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

     void vec_$ipremult16(
          short *start_vec,
          short *matrix,
          short *result_vec)

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

     procedure vec_$ipremult16(
          in start_vec: univ vec_$integer16_vector;
          in matrix: univ vec_$integer16_matrix;
          out result_vec: univ vec_$integer16_vector);

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

           integer*2 start_vec(4), matrix(4,4), result_vec(4)

           call vec_$ipremult16(start_vec, matrix, result_vec)

DESCRIPTION
     Vec_$ipremult16 multiplies the 4-element vector start_vec by the 4x4
     matrix matrix.

     In C, vec_$ipremult16 applies matrix as a left transform to a column vec-
     tor start_vec, and the resulting operation is

          for (i = 0; i < 4; ++i) {
               result_vec[i] = 0;
               for (j = 0; i < 4; ++j)
                    result_vec[i] += start_vec[i]
                                  * matrix[i][j];
          }

     In Pascal, vec_$ipremult16 applies matrix as a left transform to a column
     vector start_vec, and the resulting operation is

          for i := 1 to 4 do
               begin
               result_vec[i] := 0;
               for j := 1 to 4 do
                    result_vec[i] := result_vec[i]
                                  + start_vec[i]
                                  * matrix[i,j];
               end

     In FORTRAN, vec_$ipremult16 applies matrix as a right transform to a row
     vector start_vec, and the resulting operation is

           do 10 i = 1, 4
               result_vec(i) = 0
               do 10 j = 1, 4
                    result_vec(i) = result_vec(i)
          &                       + start_vec(j)
          &                       * matrix(j,i)
       10  continue

     start_vec
          The vector to multiply by matrix.

     matrix
          The matrix to multiply by start_vec.

     result_vec
          The product of start_vec and matrix.

NOTES
     Vec_$ipostmult16 transforms 16-bit integer vectors from the other side.

SEE ALSO
     vec_$dpremult, vec_$ipremult, vec_$premult.