#include "vogle.h"

/*
 *  premulttensor
 *
 *  Premultiply the tensor b by the matrix a and place the result
 *  into the tensor c.
 */
void
  premulttensor(c, a, b)
Tensor	b, c;
Matrix	a;
{
  register	int	i, j, k;
  float		x1, x2, x3, x4;
  
  for (i = 0; i < 4; i++)
    for (j = 0; j < 4; j++) {
      x1 = x2 = x3 = x4 = 0.0;
      for (k = 0; k < 4; k++) {
	x1 += a[i][k] * b[0][k][j];
	x2 += a[i][k] * b[1][k][j];
	x3 += a[i][k] * b[2][k][j];
	x4 += a[i][k] * b[3][k][j];
      }
      c[0][i][j] = x1;
      c[1][i][j] = x2;
      c[2][i][j] = x3;
      c[3][i][j] = x4;
    }
}

/*
 *  multtensor
 *
 *  Multiply the tensor b by the matrix a and place the result
 *  into the tensor c.
 */
void
  multtensor(c, a, b)
Tensor	b, c;
Matrix	a;
{
  register	int	i, j, k;
  float		x1, x2, x3, x4;
  
  for (i = 0; i < 4; i++)
    for (j = 0; j < 4; j++) {
      x1 = x2 = x3 = x4 = 0.0;
      for (k = 0; k < 4; k++) {
	x1 += b[0][i][k] * a[k][j];
	x2 += b[1][i][k] * a[k][j];
	x3 += b[2][i][k] * a[k][j];
	x4 += b[3][i][k] * a[k][j];
      }
      c[0][i][j] = x1;
      c[1][i][j] = x2;
      c[2][i][j] = x3;
      c[3][i][j] = x4;
    }
}

/*
 * Copy the tensor a into b.
 */
void
  copytensor(b, a)
Tensor	a, b;
{
  register	int	i, j, k;
  
  for (i = 0; i < 4; i++)
    for (j = 0; j < 4; j++)
      for (k = 0; k < 4; k++)
	b[i][j][k] = a[i][j][k];
}

/*
 * Copy the tensor a into b "transposed".
 */
void
  copytensortrans(b, a)
Tensor	a, b;
{
  register	int	i, j, k;
  
  for (i = 0; i < 4; i++)
    for (j = 0; j < 4; j++)
      for (k = 0; k < 4; k++)
	b[i][j][k] = a[i][k][j];
}
