Subj : Re: Matrix Multiplication using pointers
To   : borland.public.cpp.borlandcpp
From : "Beason Fordham" <FordhamJE@comcast.net>
Date : Mon Jan 05 2004 01:33 am

"Jeevan" <fenn_@eudoramail.com> wrote in message
news:3ff1de01$1@newsgroups.borland.com...
> Can anyone provide me with a code for matrix multiplication using the
pointers.Please do help.
>
> Jeevan

Here is a simple function for a multiplying 3X3 matrices (A * B = C)

double A[3][3], B[3][3], C[3][3];

void  MultiplyMatrices(double *A, double *B, double *C)
{
    C[0] = A[0]*B[0] + A[1]*B[3] + A[2]*B[6];
    C[1] = A[0]*B[1] + A[1]*B[4] + A[2]*B[7];
    C[2] = A[0]*B[2] + A[1]*B[5] + A[2]*B[8];

    C[3] = A[3]*B[0] + A[4]*B[3] + A[5]*B[6];
    C[4] = A[3]*B[1] + A[4]*B[4] + A[5]*B[7];
    C[5] = A[3]*B[2] + A[4]*B[5] + A[5]*B[8];

    C[6] = A[6]*B[0] + A[7]*B[3] + A[8]*B[6];
    C[7] = A[6]*B[1] + A[7]*B[4] + A[8]*B[7];
    C[8] = A[6]*B[2] + A[7]*B[5] + A[8]*B[8];
}


This is effectively passing pointers to the matrices.
Hope it helps.

Beason

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