[Performanceoptimization-wg] BBH benchmark results

I ran benchmarks on Graham for Ian's BBH benchmark parameter files. Since this measures OpenMP performance, I used a single node with 32 cores, varying the number of OpenMP threads. The results are in the repo next to the benchmark parameter files in a CSV file.

The result is: With a single OpenMP thread, as expected no difference. For many (16) OpenMP threads, the new code is twice as fast. For intermediate cases, the new code is up to 10x faster. This is clearly because the old code behaves badly.

-erik