I have searched through the archives without success. Apparently, the question is simple:
What linear algebra library can I use that is parallel (shared memory) but without OpenMP?
As far as I've seen, OpenMP seems a requirement. Since I need to interact with colleagues using a Mac, I cannot opt for OpenMP (no, I cannot ask them to compile gcc). The usage would be a classic FEM, so matrices, vectors, and decompositions (or some kind of parallel linear solver).
Intel's TBB is ok, of course, pthreads are good, standard C++
std::thread would be the perfection. But I'm not looking for perfection :)