Matrix multiplication involving pointers

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how to do i multiply matrix C(constant) and A and store the results in B? See the snippet code for the case at hand.

C#

tom.cpp file
void tom::multiply(void* btr)

{



         short* A =(short*)btr;



             int j,i;



short C[4][4]={1,1,1,1,2,1,-1,-2,1,-1,-1,1,1,-2,2,-1};

short B[4][4];

Posted 28-Sep-10 23:08pm

SMART LUBOBYA

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CPallini · Answer 1 · 2010-09-28T23:40:00

Solution 1

You know:

B<small>ik</small> = C<small>ij</small> * A<small>jk</small>

With sum on the repeated index j.

That's (probably) translates to:

for (i=0; i<4; i++)
  for (k=0; k<4; k++)
    for (j=0; j<4; j++)
      B[i][k] = C[i][j] * A[j*4+k]

in your case.

:)

Posted 28-Sep-10 23:40pm

CPallini