[dibanez]

As someone who has programmed both Phis and conventional x86 CPUs, I can confirm that the Phi is more sensitive to data traversal order and NUMA effects on which core accesses which memory. Also, the latest generation (Knights Landing) has much better performing cores than the previous generation.

[reitzensteinm]

Well, if it weren't the case and you had that core count without compromise, Phis would have come along a lot sooner with a price tag to match :)

Did you happen to use the Knight's Corner or the new Knight's Landing variant? I'd be quite interested to know how KL stacks up, as naively from the specs it seems like it should be a lot more tolerant with code (but not poor memory access patterns).

[dibanez]

Both, and it agrees with your prediction. KNL's cores are each much faster than KNC's cores. A KNC core was over 10X slower than a mainstream CPU core, and a KNL core seems to only be about 4.5X slower (on my particular code). I also get linear OpenMP scaling from 1 to 64 threads on KNL, so the parallelism is all there.

[rjtobin]

Some questions out of curiosity: Is your application bandwidth-bound / compute-bound or something else? Also what modes have you been operating the KNL chip in?

[dman]

Are you using the socketed version of the pcie version?