trick/trick_source/trick_utils/math/src/dmtxm.c

/*
   PURPOSE: (Matrix transpose times matrix)

   ASSUMPTIONS AND LIMITATIONS: ((3x3 Matrix implementation))

   PROGRAMMERS: (((Les Quiocho) (NASA/JSC) (Jan 1990) (v1.0) (Init Release))) */

#include "trick/trick_math.h"

void dmtxm(double prod[3][3],   /* Out: product of the two matrices */
           double mat1[3][3],   /* In: matrix 1 */
           double mat2[3][3])
{                                      /* In: matrix 2 */
    double trans[3][3];

    dm_trans(trans, mat1);

    prod[0][0] = trans[0][0] * mat2[0][0] + trans[0][1] * mat2[1][0] + trans[0][2] * mat2[2][0];
    prod[0][1] = trans[0][0] * mat2[0][1] + trans[0][1] * mat2[1][1] + trans[0][2] * mat2[2][1];
    prod[0][2] = trans[0][0] * mat2[0][2] + trans[0][1] * mat2[1][2] + trans[0][2] * mat2[2][2];

    prod[1][0] = trans[1][0] * mat2[0][0] + trans[1][1] * mat2[1][0] + trans[1][2] * mat2[2][0];
    prod[1][1] = trans[1][0] * mat2[0][1] + trans[1][1] * mat2[1][1] + trans[1][2] * mat2[2][1];
    prod[1][2] = trans[1][0] * mat2[0][2] + trans[1][1] * mat2[1][2] + trans[1][2] * mat2[2][2];

    prod[2][0] = trans[2][0] * mat2[0][0] + trans[2][1] * mat2[1][0] + trans[2][2] * mat2[2][0];
    prod[2][1] = trans[2][0] * mat2[0][1] + trans[2][1] * mat2[1][1] + trans[2][2] * mat2[2][1];
    prod[2][2] = trans[2][0] * mat2[0][2] + trans[2][1] * mat2[1][2] + trans[2][2] * mat2[2][2];
    return;
}