Normalize run weights before stochastic event distribution#164
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maureeungaro merged 1 commit intoJun 13, 2026
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distributeEvents drew randomNumber from U[0,1] and compared it to a running sum of the raw file weights. The weights are relative and not required to sum to 1, so for a file like "11 1 / 12 7 / 13 2" (cumulative bins 1/8/10) every draw is <= 1 and the first run always wins — runs 12 and 13 get zero events, with no warning. The code only worked when the weights happened to sum to 1. Compute the total weight once and scale each draw by it (and guard a non-positive total). Scaling the draw rather than mutating runWeights keeps the logged weight table showing the user's original values. Verified: a 1/7/2 weights file over 1000 events now distributes 97/697/206 (~10/70/20%); before, all 1000 went to the first run (Geant4 11.4.1 dev container). Fixes gemc#103 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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distributeEventsdrewrandomNumberfromU[0,1]and compared it to a running sum of the raw file weights. The weights are relative and not required to sum to 1, so for a file like11 1 / 12 7 / 13 2(cumulative bins 1/8/10) every draw is<= 1and the first run always wins — runs 12 and 13 get zero events, with no warning. The inner comment even stated the unenforced assumption.Compute the total weight once and scale each draw by it (and guard a non-positive total). Scaling the draw rather than mutating
runWeightskeeps the logged weight table showing the user's original values.Validation: a
1/7/2weights file over 1000 events now distributes 97/697/206 (~10/70/20%) in the Geant4 11.4.1 dev container; before, all 1000 went to the first run.Fixes #103