4 ms·
The Parallelism Blues: when faster code is slower
- navjack27 7y agoIs what you think you're testing actually what you're testing here? You could be threaded into hyperthreads/smt. If on Zen 1 or Zen refresh you could be hitting cross CCX communication issues. There are a number of things here that I'm just like shrugging my shoulders at, like, neat, your computer shows a behavior. Edit: what was the CPU frequency during the single core load vs the multi core load?
- itamarst 7y agoThreads per core is 1, according lscpu. This is a Xeon desktop. Here's a documented example of an OpenBLAS threading issue from someone rather more knowledgeable than I am: https://github.com/xianyi/OpenBLAS/issues/731 https://github.com/xianyi/OpenBLAS/issues/731