Programmatically find the number of cores on a machine

Question

Is there a way to determine how many cores a machine has from C/C++ in a platform-independent way? If no such thing exists, what about determining it per-platform (Windows/*

Answer 1

OpenMP is supported on many platforms (including Visual Studio 2005) and it offers a

int omp_get_num_procs();

function that returns the number of processors/cores available at the time of call.