Fast Multiplication of Three n-x-n matrices

[emaghero]

Does anybody know an algorithm for the fast multiplication of three n-x-n symmetric matrices?

I have an algorithm, which I'm not too pleased with, that does the job.

Does anybody know a faster method, or even how to improve my algorithm?

My algorithm takes three n-x-n symmetric matrices, A, B, C

It multiplies the first two in the usual way to give a matrix D = A*B.

It then calculates the product D*C and stores the result in A.

I am not happy with this as it takes far too long.

Can anybody speed it up?

The first function is the standard way in which matrix multiplication is performed

void Matrix_Multiply(double *mat_one,double *mat_two,double *mat_result,double &size)
{
    for(int i=0;i<(int)(size);i++){
        for(int j=0;j<(int)(size);j++){
            for(int k=0;k<(int)(size);k++){
                *(mat_result+(int)(i*size)+j)+=*(mat_one+(int)(i*size)+k)**(mat_two+(int)(k*size)+j);
            }
        }
    }
}
 

The second function calls the first to perform two matrix multiplications and then stores the result

void Matrix_Triple_Product(double *mat_one,double *mat_two,double *mat_three,void (*g)(double *,double *,double *,double &),double &size)
{
    double *mat_temp=new(double [(int)(size)*(int)(size)]);//Array to hold the result of the first multiplication
    for(int i=0;i<(int)(size);i++){
        for(int j=0;j<(int)(size);j++){
            *(mat_temp+(int)(i*size)+j)=0.0;
        }
    }
    //Calculate the product of the first two matrices and store the result in mat_temp
    g(mat_one,mat_two,mat_temp,size);
    //Assign the second matrix to zero
    for(int i=0;i<(int)(size);i++){
        for(int j=0;j<(int)(size);j++){
            *(mat_two+(int)(i*size)+j)=0.0;
        }
    }
    //Calculate the product of mat_temp and the third matrix and store the result in the second matrix
    g(mat_temp,mat_three,mat_two,size);
 
    cout<<"The matrix product has been computed and is stored in memory\n";
 
    delete[] mat_temp;
 
}
 

[vpawizard]

Try Strassen Algorithm for fast matrix multiplication