zen_type& operator *= ( const zen_type & other )
{
zen_type& zen = static_cast<zen_type&>( *this );
assert( zen.col() == other.row() );
static const size_type threshold = 17;
const size_type max_dims = std::max( std::max( zen.row(), zen.col() ), other.col() );
const size_type min_dims = std::min( std::min( zen.row(), zen.col() ), other.col() );
if ( ( max_dims < threshold ) || ( min_dims == 1 ) ) {
return direct_multiply( other );
}
const size_type R = zen.row();
const size_type C = zen.col();
const size_type OC = other.col();
if ( R & 1 )
{
if ( R & 2 ) {
return rr1( other );
}
return rr2( other );
}
if ( C & 1 )
{
if ( C & 2 ) {
return cc1( other );
}
return cc2( other );
}
if ( OC & 1 )
{
if ( OC & 2 ) {
return oc1( other );
}
return oc2( other );
}
return strassen_multiply( other );
}
/*
Function: strassen_multiply
--------------------------
Internal function. Matrix multiplication through Strenssen algorithm.
Calculates C = AB. Dimensions of A and B must be power of 2.
Parameters:
a - matrix A
rA_s - row start index of A
rA_e - row end index of A
cA_s - column start index of A
cA_e - column end index of A
b - matrix B
rB_s - column start index 0f B
rB_e - column end index of B
cB_s - column start index of B
cB_e - column end index of B
c - result matrix
*/
void strassen_multiply(
double **a, int rA_s, int rA_e, int cA_s, int cA_e,
double **b, int rB_s, int rB_e, int cB_s, int cB_e, double **c) {
if (((cA_e - cA_s) < 1) || ((rA_e - rA_s) < 1) ||
((cB_e - cB_s) < 1) ||
((cA_e - cA_s + 1 < SMALL_DIM) &&
(rA_e - rA_s + 1 < SMALL_DIM) &&
(cB_e - cB_s + 1 < SMALL_DIM))) {
for (int i = 0; i <= (rA_e - rA_s); ++i) {
for (int j = 0; j <= (cB_e - cB_s); ++j) {
c[i][j] = 0;
for (int k = 0; k <= (cA_e - cA_s); ++k) {
c[i][j] += a[i + rA_s][k + cA_s] * b[k + rB_s][j + cB_s];
}
}
}
}
else {
// Intermediate matrix initialization
double ***m = (double***)malloc(7 * sizeof(double**));
double ***c_sub = (double***)malloc(4 * sizeof(double**));
int mR = rA_e - rA_s + 1;
int mC = cB_e - cB_s + 1;
for (int i = 0; i < 7; ++i) {
m[i] = (double**)malloc((mR / 2) * sizeof(double*));
for (int j = 0; j < mR / 2; ++j) {
m[i][j] = (double*)malloc((mC / 2) * sizeof(double));
}
}
// Gets results of 7 intermediate matrices
int rA_m = (rA_s + rA_e) / 2;
int cA_m = (cA_s + cA_e) / 2;
int rB_m = (rB_s + rB_e) / 2;
int cB_m = (cB_s + cB_e) / 2;
// Temporary pointers
double **temp1;
double **temp2;
// Matrix m1
temp1 = matrix_sum(a, rA_s, rA_m, cA_s, cA_m, rA_m + 1, rA_e,
cA_m + 1, cA_e);
temp2 = matrix_sum(b, rB_s, rB_m, cB_s, cB_m, rB_m + 1, rB_e,
cB_m + 1, cB_e);
strassen_multiply(temp1, 0, rA_m - rA_s, 0, cA_m - cA_s, temp2,
0, rB_m - rB_s, 0, cB_m - cB_s, m[0]);
clear2D(&temp1, rA_m - rA_s + 1);
clear2D(&temp2, rB_m - rB_s + 1);
// Matrix m2
temp1 = matrix_sum(a, rA_m + 1, rA_e, cA_s, cA_m, rA_m + 1,
rA_e, cA_m + 1, cA_e);
strassen_multiply(temp1, 0, rA_m - rA_s, 0, cA_m - cA_s,
b, rB_s, rB_m, cB_s, cB_m, m[1]);
clear2D(&temp1, rA_e - rA_m);
// Matrix m3
temp1 = matrix_sub(b, rB_s, rB_m, cB_m + 1, cB_e, rB_m + 1,
rB_e, cB_m + 1, cB_e);
strassen_multiply(a, rA_s, rA_m, cA_s, cA_m, temp1, 0,
rB_m - rB_s, 0, cB_m - cB_s, m[2]);
clear2D(&temp1, rB_m - rB_s + 1);
// Matrix m4
temp1 = matrix_sub(b, rB_m + 1, rB_e, cB_s, cB_m, rB_s, rB_m,
cB_s, cB_m);
strassen_multiply(a, rA_m + 1, rA_e, cA_m + 1, cA_e, temp1,
0, rB_m - rB_s, 0, cB_m - cB_s, m[3]);
clear2D(&temp1, rB_e - rB_m);
// Matrix m5
temp1 = matrix_sum(a, rA_s, rA_m, cA_s, cA_m, rA_s, rA_m,
cA_m + 1, cA_e);
strassen_multiply(temp1, 0, rA_m - rA_s, 0, cA_m - cA_s, b,
rB_m + 1, rB_e, cB_m + 1, cB_e, m[4]);
clear2D(&temp1, rA_m - rA_s + 1);
// Matrix m6
temp1 = matrix_sub(a, rA_m + 1, rA_e, cA_s, cA_m, rA_s, rA_m,
cA_s, cA_m);
temp2 = matrix_sum(b, rB_s, rB_m, cB_s, cB_m, rB_s, rB_m,
cB_m + 1, cB_e);
strassen_multiply(temp1, 0, rA_m - rA_s, 0, cA_m - cA_s,
temp2, 0, rB_m - rB_s, 0, cB_m - cB_s, m[5]);
clear2D(&temp1, rA_e - rA_m);
clear2D(&temp2, rB_m - rB_s + 1);
// Matrix m7
temp1 = matrix_sub(a, rA_s, rA_m, cA_m + 1, cA_e, rA_m + 1,
rA_e, cA_m + 1, cA_e);
temp2 = matrix_sum(b, rB_m + 1, rB_e, cB_s, cB_m, rB_m + 1,
rB_e, cB_m + 1, cB_e);
strassen_multiply(temp1, 0, rA_m - rA_s, 0, cA_m - cA_s, temp2,
0, rB_m - rB_s, 0, cB_m - cB_s, m[6]);
clear2D(&temp1, rA_m - rA_s + 1);
clear2D(&temp2, rB_e - rB_m);
// Calculates all result sub-matrices
temp1 = sum(m[0], m[3], mR / 2, mC / 2);
temp2 = sub(temp1, m[4], mR / 2, mC / 2);
c_sub[0] = sum(temp2, m[6], mR / 2, mC / 2);
clear2D(&temp1, mR / 2);
clear2D(&temp2, mR / 2);
c_sub[1] = sum(m[2], m[4], mR / 2, mC / 2);
c_sub[2] = sum(m[1], m[3], mR / 2, mC / 2);
temp1 = sum(m[0], m[2], mR / 2, mC / 2);
temp2 = sum(temp1, m[5], mR / 2, mC / 2);
c_sub[3] = sub(temp2, m[1], mR / 2, mC / 2);
clear2D(&temp1, mR / 2);
clear2D(&temp2, mR / 2);
// Free intermediate matrices
for (int i = 0; i < 7; ++i) {
for (int j = 0; j < mR / 2; ++j) {
free(m[i][j]);
}
free(m[i]);
}
free(m);
// Combine sub-matrices
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < mR / 2; ++j) {
for (int k = 0; k < mC / 2; ++k) {
c[(i / 2) * mR / 2 + j][(i % 2) * mC / 2 + k] =
c_sub[i][j][k];
}
}
}
// Free sub mmatrices
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < mR / 2; ++j) {
free(c_sub[i][j]);
}
free(c_sub[i]);
}
free(c_sub);
}
}
