[petsc-users] interpreting petsc streams result

[Klaij, Christiaan]

Attached is a petsc streams result kindly provided by a hardware
vendor for a single compute node, dual socket, with two AMD epyc
9355 processors. Each processor has 32 cores, 12 DDR5 memory
channels and mem BW around 600 GB/s.

* It is not immediately clear which line corresponds to which
  y-axis. Could future versions of petsc please color the axis
  label with the matching line color? 

* Why would the achieved bandwidth be roughly 0.9 x 1e6 MB/s =
  900 GB/s and not closer to 1200 GB/s? 

* The speed-up seems to be 12 out of 64, provided multiples of 8
  cores are used. As expected given 12 memory channels?

* Does the zig-zag pattern indicate a pinning problem, or is it
  unavoidable given the 8 core building block of these type of
  processors?

Chris
dr. ir. Christiaan Klaij | senior researcher
Research & Development | CFD Development
T +31 317 49 33 44 | https://urldefense.us/v3/__http://www.marin.nl__;!!G_uCfscf7eWS!fqSBpN3Ld5fjzXGShGI09uJke12M-5LukEHe-y-gw0Bw9msZeH7wNiId6DZxQpluR_RUWpuoQWUD2HSsmmm_T4I$ 
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