Pythia8 seeding improvements #1695
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sawenzel
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benedikt-voelkel and
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| auto seed = (gRandom->TRandom::GetSeed() % 900000000); | ||
| myGen->setUsedSeed(seed); | ||
| myGen->readString("Random:setSeed on"); | ||
| myGen->readString("Random:seed " + std::to_string(seed)); | ||
| myGen->setInitialSeed(seed); |
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Hi @sawenzel, if I understood correctly the implementation in AliceO2Group/AliceO2#13281, this part is now redundant and can be removed, since it does exactly the steps performed when no specific seed is provided (i.e. takes it from ROOT)
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Hi @fcatalan92 : Yes, I think we could simplify this further by taking away even the auto seed = ; ... setInitialSeed() steps. But I wasn't sure if this breaks something because of setUsedSeed.
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Indeed, after some recent developments for Pb-Pb HF productions, setUsedSeed is used to store the seed in our custom generator. This seed is later accessed by generator_pythia8_embed_hf.C to select a pT-hard bin.
I wonder if a getter to the used seed could be added to GeneratorPythia8, this will allow us to simplify our custom generators. In this case, I think the seed should be updated when calling GeneratorPythia8::seedGenerator().
At this point, all looks good to me for this PR. I can take care of updating the HF generators later on, if the development I proposed is done.
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This commit harmonizes the seeding procedure of generators based on o2::eventgen::GeneratorPythia8, following a development done in O2 (AliceO2Group/AliceO2#13281) In principle, o2::eventgen::GeneratorPythia8 now performs it's own seeding within the Init function. This seeding makes sure to integrate with the `--seed` command line option of our event generation executable. The commit: * Removes seeding code in O2DPG when it would override the default behaviour from O2. * Uses a new dedicated function `setInitialSeed` instead of manipulating Pythia8 with config strings (in situations in which the user targets seeding based on ALIEN_PROC_ID for instance). * Ensures that event generation becomes more repeatable in situations when the same `--seed` is given to the event generation executable. This may help to debug crashes on the GRID etc.
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| auto seed = (gRandom->TRandom::GetSeed() % 900000000); | ||
| myGen->setUsedSeed(seed); | ||
| myGen->readString("Random:setSeed on"); | ||
| myGen->readString("Random:seed " + std::to_string(seed)); | ||
| myGen->setInitialSeed(seed); |
There was a problem hiding this comment.
Indeed, after some recent developments for Pb-Pb HF productions, setUsedSeed is used to store the seed in our custom generator. This seed is later accessed by generator_pythia8_embed_hf.C to select a pT-hard bin.
I wonder if a getter to the used seed could be added to GeneratorPythia8, this will allow us to simplify our custom generators. In this case, I think the seed should be updated when calling GeneratorPythia8::seedGenerator().
At this point, all looks good to me for this PR. I can take care of updating the HF generators later on, if the development I proposed is done.
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simplification of seeding code and harmonization thereof