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openmpi: make build reproducible and fix compiler wrappers #58964

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merged 2 commits into from Sep 15, 2019
Merged

openmpi: make build reproducible and fix compiler wrappers #58964

merged 2 commits into from Sep 15, 2019

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markuskowa
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Motivation for this change

The build system integrates various time stamps (+user, hostname) into the output thus creating an irreducible build.

The MPI compiler wrappers should point to the compilers used at build time per default. For MPICH this feature is already in the derivation (#44555)

Things done
  • Patch in fixed timestamps, usernames, and hostname
  • Set absolute path names for MPI compiler wrappers.
  • Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
  • Built on platform(s)
    • NixOS
    • macOS
    • other Linux distributions
  • Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
  • Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
  • Tested execution of all binary files (usually in ./result/bin/)
  • Determined the impact on package closure size (by running nix path-info -S before and after)
  • Assured whether relevant documentation is up to date
  • Fits CONTRIBUTING.md.

FRidh
FRidh reviewed Apr 7, 2019
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pkgs/development/libraries/openmpi/default.nix Outdated
# default compilers should be indentical to the
# compilers at build time

sed -i 's:compiler=.*:compiler=${stdenv.cc}/bin/cc:' $out/share/openmpi/mpicc-wrapper-data.txt
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Is this correct in the case of cross-compilation?

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@markuskowa markuskowa Apr 7, 2019 •
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Cross compilation is still a mystery to me but this probably only works if hostPlatform == buildPlatform. How would I get the compilers of the target platform? cc @Mic92

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@Mic92 Mic92 Apr 12, 2019 •
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@markuskowa I think this would be ${targetPackages.stdenv.cc}

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But actually there was this one recently introduced: #57611
So instead this would be:

"${pkgsTargetTarget.stdenv.cc}/bin/${pkgsTargetTarget.stdenv.cc.targetPrefix}cc"

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@Ericson2314 could maybe also provide the right expression for gfortran.

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Thanks for the insight! Just extrapolating from the expression for gcc:

${pkgsTargetTarget.gfortran}/bin/${pkgsTargetTarget.gfortran.targetPrefix}gfortran

Does that make sense? EDIT: it yields the right result when I build locally.

@markuskowa
openmpi: make build reproducible
8cf3752 
fix:
* build and configure time stamps
* build and configure user
@markuskowa
openmpi: use absolute paths compiler wrapper
e23e116 
The MPI compiler wrappers should point to the
compilers used at build time per default.
@bjornfor bjornfor merged commit 3857d3d into NixOS:master Sep 15, 2019
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Thanks!

@markuskowa markuskowa deleted the fix-ompi-repro branch September 15, 2019 18:33
@abbradar
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abbradar commented Oct 3, 2019

This semi-breaks cntk because it needs GCC7 on one hand and uses mpic++ on another so replacing stdenv doesn't help. I'd expect mpic++ to use whatever compiler is currently in PATH by default, what is the right way to fix that?

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Mic92 commented Oct 3, 2019

@abbradar is it not common to set OMPI_CC to set a different compiler?

@markuskowa
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@abbradar setting OMPI_CXX should override the C++ compiler. To avoid problems with different libstdc++ versions you could also override the stdenv of openmpi. That way your application and openmpi are built with the same compiler.

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abbradar commented Oct 4, 2019 •
edited

@Mic92 @markuskowa Yep, that's the answer I needed. Thanks!

@markuskowa markuskowa mentioned this pull request Jan 23, 2024
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@markuskowa @bjornfor @abbradar @Mic92 @FRidh @GrahamcOfBorg