Day: May 28, 2012

If you are writing something involving the math between vectors in C/C++, you may want to check out Vlfeat (http://vlfeat.org).

It is designed to be a library for Computer Vision related stuff, but it also bring you a wrapper for SSE2 acceleration for vector computation.

Say your original code for the calculation of vectors product looks like this:

float productOfVectors(const float *vecA, const float *vecB, const int dimension) {
   float value = 0.0f;
   for (int i = 0; i < dimension; i++)
   {
        value += (vecA[i] * vecB[i]);
   }
   return value;
}

It can save you time significantly by adding vlfeat to your project and replace it with this:

float productOfVectors(const float *vecA, const float *vecB, const int dimension) {
   float value = 0.0f;
   vl_eval_vector_comparison_on_all_pairs_f(&value, dimension, vecA, 1, vecB, 1, vl_get_vector_comparison_function_f(VlKernelL2));
   return value;
}

It's pretty easy but it really works. It takes use of the SSE2 instructions provided by your CPU which result in an non-trivial acceleration when you are doing large scale computation.

You can find more supported forms of calculation here, thanks for the developer's good job.