There is a self tuning linear algebra library called ATLAS. When building, probes various things about your computer, things like L1/L2 cache, if you have fused

There is a self tuning linear algebra library called ATLAS. When building, probes various things about your computer, things like L1/L2 cache, if you have fused multiply/add, etc. It uses these to output very highly tuned matrix kernels in standard C. Ironically, when compiling this C code, you have to use -O, higher optimization levels make the compiler try to be too smart for its own good and actually perform worse.