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Fix MadGraph: Pythia8 shower chain and conf relocation - #6274

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ktf merged 1 commit into
alisw:masterfrom
jackal1-66:newMadFix
Aug 16, 2026
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Fix MadGraph: Pythia8 shower chain and conf relocation#6274
ktf merged 1 commit into
alisw:masterfrom
jackal1-66:newMadFix

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@jackal1-66

@jackal1-66 jackal1-66 commented Jul 12, 2026

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Multiple fixes applied:

  • madgraph.sh → 1) fix to HepMC2 path inside Pythia8 MakeFile.inc; 2) No more dummy configurations and runtime patching. Everything is done using the relative ./, which is understood by MG5.
  • lhapdf.sh → I noticed /local/workspace/etc was set in the symlink which was clearly not right and it was causing Failed to access python version of LHAPDF. While digging I saw that the recipe created lib/python with find $PWD ... ln -nfs {} python, so with an absolute symlink frozen to the build-time INSTALLROOT. The applied fix creates a relative symlink (python -> python3.10), valid at any install prefix (tested locally and with an alice-docker fresh install).
  • pythia.sh → Pythia8 is now built with zlib. Before gzipped hepmc files could not be read, making the MG5 Pythia8 interface hang indefinitely.
    @ktf let me know what you think... If we're caching by node on the GRID this solution should also work as the configuration will be the same for all the jobs in a node if they can access the /tmp folder, but please correct me if I'm wrong.

@jackal1-66
jackal1-66 requested review from a team as code owners July 12, 2026 20:04
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@ktf this should now work and be compatible with the GRID nodes as well, could you have a look?

@ktf
ktf merged commit 0753801 into alisw:master Aug 16, 2026
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2 participants