Fix seed logic to ensure reproducibility#3192
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can you add tests to ensure the original bug is now discovered (and the fixed with this PR)? |
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Summary
This PR fixes a bug in
Model.__init__whereself._seedwas incorrectly set toNoneeven when a validrng(integer) was provided. This ensures that theScenarioinstance is initialized with the correct seed and thatreset_randomizer()works as intended.Bug / Issue
Closes #3190
Implementation
I refactored the initialization logic in
mesa/model.pyto use atry-except-elsepattern, strictly separating seed generation from validation.rng=None): Explicitly generates and stores an integer seed. This ensures post-hoc reproducibility (users can checkmodel.scenario.rngto debug a random run that wasn't explicitly seeded).rng=42): Theelseblock now correctly capturesseed = rngwhenrandom.Random(rng)succeeds.rng=Generator): Theexceptblock handles Numpy generators by extracting a valid integer seed.