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strassen.cpp
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strassen.cpp
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#include<iostream>
#include<vector>
using namespace std;
#define THRESHOLD 2
//int **MATRIX_A, **MATRIX_B, **PRODUCT;
vector< vector<int> > MATRIX_A(1, vector<int>(1,0));
vector< vector<int> > MATRIX_B(1, vector<int>(1,0));
vector< vector<int> > PRODUCT(1, vector<int>(1,0));
/*---------- Function prototyping ----------
*void strassen(vector< vector<int> > *, vector< vector<int> > *, vector< vector<int> > *, int);
*void addMatrix(vector< vector<int> > *, vector< vector<int> > *, vector< vector<int> > *, int);
*void subtractMatrix(vector< vector<int> > *, vector< vector<int> > *, vector< vector<int> > *, int);
*void multiplyMatrix(vector< vector<int> > *, vector< vector<int> > *, vector< vector<int> > *, int);
*/
int main()
{
/*---------- VARIABLES DECLARATION ---------- */
int matrix_size, count = 0, i,j;
/*---------- INPUT ARRAY SIZE ---------- */
std::cout<<"Input size of the square matrix (Mazimum is 32): ";
std::cin>>matrix_size;
/*---------- MEMORY ALLOCATION OF ARRAYS (vectors make it easy!!) ---------- */
/*MATRIX_A = new int*[matrix_size];
MATRIX_B = new int*[matrix_size];
PRODUCT = new int*[matrix_size];
for(i=0;i<matrix_size;i++) {
MATRIX_A[i] = new int[matrix_size];
MATRIX_B[i] = new int[matrix_size];
PRODUCT[i] = new int[matriz_size];
for(j=0;j<matrix_size;j++) {
MATRIX_A[i][j]=MATRIX_B[i][j]=PRODUCT[i][j]=count;
}
}
*/
/*---------- Allocation of memory for Vector data members ---------- */
for(int i=0;i<matrix_size;i++) {
MATRIX_A.resize(matrix_size);
MATRIX_B.resize(matrix_size);
PRODUCT.resize(matrix_size);
for(j=0;j<matrix_size;j++) {
MATRIX_A[j].resize(matrix_size);
MATRIX_B[j].resize(matrix_size);
PRODUCT[j].resize(matrix_size);
}
}
/*---------- INPUT MATRIX_A ---------- */
std::cout<<"Enter the elements MATRIX A (row wise) "<<matrix_size<<" per row: "<<endl;
for(i=0;i<matrix_size;i++) {
std::cout<<"Enter elements for row "<<i+1<<":";
for(j=0;j<matrix_size;j++)
std::cin>>MATRIX_A[i][j];
}
/*---------- INPUT MATRIX_B ---------- */
std::cout<<"Enter the elements MATRIX B (row wise) "<<matrix_size<<" per row: "<<endl;
for(i=0;i<matrix_size;i++) {
std::cout<<"Enter elements for row "<<i+1<<":";
for(j=0;j<matrix_size;j++)
std::cin>>MATRIX_B[i][j];
}
strassen(&MATRIX_A, &MATRIX_B, &PRODUCT, matrix_size);
/*---------- OUTPUT OF RESULTS (RESULTANT MATRIX) ---------- */
for(i=0;i<matrix_size;i++) {
for(j=0;j<matrix_size;j++)
std::cout<<PRODUCT[i][j]<<" ";
cout<<endl;
}
return 0;
}
void strassen(vector< vector<int> > *a, vector< vector<int> > *b, vector< vector<int> > *result, int current_matrix_size)
{
int next_matrix_size;
vector< vector<int> > a1(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > a2(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > a3(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > a4(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > b1(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > b2(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > b3(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > b4(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > p1(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > p2(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > p3(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > p4(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > p5(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > p6(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > p7(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > r(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > s(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > t(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > u(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > subtract_result(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > add_result1(current_matrix_size, vector<int>(current_matrix_size,0));
vector< vector<int> > add_result2(current_matrix_size, vector<int>(current_matrix_size,0));
if(current_matrix_size<=THRESHOLD) {
multiplyMatrix(a,b,result,current_matrix_size);
}
else {
next_matrix_size = current_matrix_size/2;
for (int ii=0;ii<next_matrix_size;ii++) {
for (int jj=0;jj<next_matrix_size;jj++) {
a1[ii][jj] = (a->at(ii)).at(jj);
a2[ii][jj] = (a->at(ii)).at(jj+next_matrix_size);
a3[ii][jj] = (a->at(ii+next_matrix_size)).at(jj);
a4[ii][jj] = (a->at(ii+next_matrix_size)).at(jj+next_matrix_size);
b1[ii][jj] = (b->at(ii)).at(jj);
b2[ii][jj] = (b->at(ii)).at(jj+next_matrix_size);
b3[ii][jj] = (b->at(ii+next_matrix_size)).at(jj);
b4[ii][jj] = (b->at(ii+next_matrix_size)).at(jj+next_matrix_size);
}
}
/* p1 calculation */
subtractMatrix(&b2,&b4,&subtract_result,next_matrix_size);
strassen(&a1,&subtract_result,&p1,next_matrix_size);
/* p2 caculation */
addMatrix(&a1,&a2,&add_result1,next_matrix_size);
strassen(&add_result1,&b4,&p2,next_matrix_size);
/* p3 calculation */
addMatrix(&a3,&a4,&add_result1,next_matrix_size);
strassen(&add_result1,&b1,&p3,next_matrix_size);
/*p4 calculation */
subtractMatrix(&b3,&b1,&subtract_result,next_matrix_size);
strassen(&a4,&subtract_result,&p4,next_matrix_size);
/* p5 calculation */
addMatrix(&a1,&a4,&add_result1,next_matrix_size);
addMatrix(&b1,&b4,&add_result2,next_matrix_size);
strassen(&add_result1,&add_result2,&p5,next_matrix_size);
/* p6 calculation */
subtractMatrix(&a2,&a4,&subtract_result,next_matrix_size);
addMatrix(&b3,&b4,&add_result1,next_matrix_size);
strassen(&subtract_result,&add_result1,&p6,next_matrix_size);
/* p7 calculation */
subtractMatrix(&a1,&a3,&subtract_result,next_matrix_size);
addMatrix(&b1,&b2,&add_result1,next_matrix_size);
strassen(&subtract_result,&add_result1,&p7,next_matrix_size);
/* r calculation */
addMatrix(&p5,&p4,&add_result1,next_matrix_size);
subtractMatrix(&add_result1,&p2,&subtract_result,next_matrix_size);
addMatrix(&subtract_result,&p6,&r,next_matrix_size);
/* s calculation */
addMatrix(&p1,&p2,&s,next_matrix_size);
/* t calulation */
addMatrix(&p3,&p4,&t,next_matrix_size);
/* u calculation */
addMatrix(&p5,&p1,&add_result1,next_matrix_size);
subtractMatrix(&add_result1,&p3,&subtract_result,next_matrix_size);
subtractMatrix(&subtract_result,&p7,&u,next_matrix_size);
for(int ii=0;ii<next_matrix_size;ii++) {
for(int jj=0;jj<next_matrix_size;jj++) {
(result->at(ii)).at(jj)=r[ii][jj];
(result->at(ii)).at(jj+next_matrix_size)=s[ii][jj];
(result->at(ii+next_matrix_size)).at(jj)=t[ii][jj];
(result->at(ii+next_matrix_size)).at(jj+next_matrix_size)=u[ii][jj];
}
}
}
}
void addMatrix(vector< vector<int> > *m1,vector< vector<int> > *m2,vector< vector<int> > *add_result, int matrix_size)
{
for(int ii=0;ii<matrix_size;ii++) {
for(int jj=0;jj<matrix_size;jj++) {
(add_result->at(ii)).at(jj)=(m1->at(ii)).at(jj)+(m2->at(ii)).at(jj);
}
}
}
void subtractMatrix(vector< vector<int> > *m1,vector< vector<int> > *m2,vector< vector<int> > *subtract_result, int matrix_size)
{
for(int ii=0;ii<matrix_size;ii++) {
for(int jj=0;jj<matrix_size;jj++) {
(subtract_result->at(ii)).at(jj)=(m1->at(ii)).at(jj)-(m2->at(ii)).at(jj);
}
}
}
void multiplyMatrix(vector< vector<int> > *m1,vector< vector<int> > *m2,vector< vector<int> > *multiply_result, int matrix_size)
{
for(int ii=0;ii<matrix_size;ii++) {
for(int jj=0;jj<matrix_size;jj++) {
(multiply_result->at(ii)).at(jj)=0;
for(int kk=0;kk<matrix_size;kk++) {
(multiply_result->at(ii)).at(jj)+=(m1->at(ii)).at(kk)*(m2->at(kk)).at(jj);
}
}
}
}