fix: invert the probability of acceptance in fading tabu#2358
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No need for Fred to review; Chris knows what this is about. |
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Pull request overview
This PR aims to prevent deterministic fading-tabu accept/reject decisions from unnecessarily consuming RNG state during local search tabu acceptance.
Changes:
- Introduce a helper method that only calls
nextDouble()when0.0 < acceptChance < 1.0. - Refactor fading-tabu acceptance logic to delegate RNG usage to the helper.
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The logic is wrong, taking it back to draft. |
Christopher-Chianelli
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Jun 11, 2026
triceo
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…d else-if Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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| private FadingTabuDecision decideFadingTabuAcceptance(LocalSearchMoveScope<Solution_> moveScope, int fadingTabuStepCount) { | ||
| // Invert the chance; the longer the element is in the tabu list, the higher the chance should be. | ||
| var numerator = workingFadingTabuSize - fadingTabuStepCount; | ||
| if (numerator <= 0) { // The inverted chance would be >= 1. | ||
| return FadingTabuDecision.CERTAIN; |
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The closer the item is to becoming non-tabu, the higher should its acceptance probability be. (This has been a long-standing bug which went unnoticed.)
Also made sure that, when the chance is 0 or 1, that the RNG is not called. RNG is expensive, and it affects randomness in other places of the solver that use the same RNG.