matrix multiplication in c code

Question

I have a code needs to do some matrix multiplication like

    ML2=ML+uMc+c1+c2
    MC2=v*ML+(u*v+1)*Mc+c2

Where ML is MXM matrix of

    ML=[1 1 1 1....1;2 2 2 2...2......;M M M.....M]
    MC=[1 2 3 4 ...M;1 2 3 4...M......;1 2 3.....M]

u,v,c1 and c2 are constant of 8 bit.

I want to find the values of ML2,MC2 in fast execution time using any fast library

I think [this question](http://stackoverflow.com/questions/4501322/c-libraries-for-mathematical-matrix-operations) will help you out. — Josh, Jun 17 '13 at 13:37

score 1 · Answer 1 · answered Jun 17 '13 at 13:50

You did not state the platform you want this for but for matrix operations nothing is faster than the Intel Math Kernel Library for Intel CPUs

http://software.intel.com/en-us/intel-mkl

This gets as close as I have seen to the peak flops possible on the CPU. MKL, however, is expensive and closed source. If you want a good open sourced and free alternative then check out Eigen. This uses C++ but I don't know if you're really restricted to C only code. Eigen also works well on other hardware such as AMD (Intel cripples it's library on AMD CPUs) and ARM.

http://eigen.tuxfamily.org/index.php?title=3.0

A third option to write one yourself. After a few weeks of effort it should not be too difficult to beat Eigen with AVX and OpenMP (Eigen only supports SSE) but it's highly unlikely you will beat MKL.

Thanks for all, But I need fast free library to make matrix multiplication in C code, not other languages, also the op is windows 32 bit — Mousa Farajallah, Jun 17 '13 at 14:22

score 0 · Answer 2 · answered Jun 17 '13 at 13:37

0

For multiplication of matrixA(AxB) and matrixB(BxC) matrix to result in matrixC(AxC)

for(int i=0;i<l;i++)
{
    for(int j=0;j<n;j++)
    {
        matrixC[i][j]=0;
        for(int k=0;k<m;k++)
        {
            matrixC[i][j]=matrixC[i][j]+(matrixA[i][k] * matrixB[k][j]);
        }
    }
}

answered Jun 17 '13 at 13:37

pcbabu

2,219
4
22
32

1

That's the naive implementation of matrix multiplication which is highly inefficient. It's likely to get less than 1% of the efficiency of the peak FLOPS/s of the CPU. The OP asked for a fast library. – Jun 17 '13 at 14:00

score 0 · Answer 3 · answered Jun 18 '13 at 12:49

0

Since ML is bunch of identical vectors 1:M, and MC is just the transpose of ML, you don't need general matrix multiplication. You can take algebraic short-cuts.

answered Jun 18 '13 at 12:49

Mike Dunlavey

40,059
14
91
135

matrix multiplication in c code

3 Answers3