As for efficiency: it depends on exactly what code you use and what your problem is. BAGEL, which included hand-coded assembly http://usqcd-software.github.io/

As for efficiency: it depends on exactly what code you use and what your problem is. BAGEL, which included hand-coded assembly http://usqcd-software.github.io/bagel_qdp/ http://usqcd-software.github.io/bagel_qdp/ was getting something like 25% of peak, sustained, for doing linear solves on the BG/Q. On a POWER8/NVIDIA P100 machine I know QUDA gets 20% of peak, sustained.