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Enable oversubscribing in OpenMPI 2.X #3335

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merged 3 commits into from
Nov 22, 2019
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@jngrad jngrad commented Nov 21, 2019

Fixes #3333

Centralize the TEST_NP and MPIEXEC_OVERSUBSCRIBE default value
deduction mechanism to the dedicated unit_test module.
The OpenMPI -oversubscribe feature was backported to the 2.X series.
Without the -oversubscribe flag, tests running on hyperthreaded CPUs
with more threads than cores using OpenMPI 2.X may exit early with
an exit code of 0, causing these tests to silently fail.
When no default value is provided for TEST_NP, value `nproc / 2 + 1`
is used instead, which can be large on hyperthreaded CPUs. This leads
to issues in parallel tests that don't scale well with a large number
of cores (e.g. when there aren't enough particles) or with a large
odd number of cores (e.g. LB or P3M).
@jngrad jngrad added this to the Espresso 4.1.2 milestone Nov 21, 2019
@jngrad jngrad requested a review from mkuron November 21, 2019 17:48
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codecov bot commented Nov 21, 2019

Codecov Report

Merging #3335 into python will decrease coverage by <1%.
The diff coverage is n/a.

Impacted file tree graph

@@          Coverage Diff           @@
##           python   #3335   +/-   ##
======================================
- Coverage      86%     86%   -1%     
======================================
  Files         538     538           
  Lines       25350   25350           
======================================
- Hits        21834   21833    -1     
- Misses       3516    3517    +1
Impacted Files Coverage Δ
src/core/electrostatics_magnetostatics/p3m.cpp 85% <0%> (-1%) ⬇️

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If you‘ve checked that OpenMPI 2.0.0 already had this option, then this is fine.

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jngrad commented Nov 22, 2019

Yes, I checked the source code. I've also now compiled 2.0.0 on Fedora 31 and the -oversubscribe flag is recognized.

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jngrad commented Nov 22, 2019

bors r=fweik

bors bot added a commit that referenced this pull request Nov 22, 2019
3334: Update io.rst r=jngrad a=jonaslandsgesell

link to h5md plugin for VMD

3335: Enable oversubscribing in OpenMPI 2.X r=fweik a=jngrad

Fixes #3333

3336: Fallthrough and remove duplicate line r=jngrad a=hirschsn

Description of changes:
 - Remove a duplicated line in `topology_check_resort` by falling through as done for other cell systems in this function.


PR Checklist
------------
 - [ ] Tests?
   - [ ] Interface
   - [ ] Core 
 - [ ] Docs?


Co-authored-by: Jonas Landsgesell <[email protected]>
Co-authored-by: Jean-Noël Grad <[email protected]>
Co-authored-by: Steffen Hirschmann <[email protected]>
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bors bot commented Nov 22, 2019

Build succeeded

@bors bors bot merged commit d1440da into espressomd:python Nov 22, 2019
@jngrad jngrad deleted the fix-3333 branch January 18, 2022 12:08
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some python tests fail silently on some architectures with OpenMPI 2.X
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