I have been running an MKL DGEMM benchmark in native mode on a KNC card, but have noticed strange behavior. The performance is inconsistent and varies quite a bit. I tried multiple thread affinity settings and noticed the same behavior with varying numbers of threads and threads per core. The test consists of calling DGEMM for a set of 6,000 by 6,000 matrices a total of 1,000 times so I can compare calls. During my testing the performance varied by as much as 100 GFLOPS. A Google search did not reveal much. However, I did find a Dr. Dobb's article that noted the unusual behavior and attributed it to OS jitter, but did not ellaborate. Has anyone else noticed this behavior?
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