Compute the triangular variance from the side widths - #57
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The textbook form squared the raw bounds, so bounds large next to their spread cancelled to 0 or a negative variance. The mean is now measured from the lower bound so it cannot overflow near double.MaxValue. Fixes #49 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01VPis8BNX5ETFM2XytgJCz7
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01VPis8BNX5ETFM2XytgJCz7
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This was referenced Sep 28, 2026
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Fixes #49
What changed
TriangularDistributionProvider.Varianceused(a² + b² + c² − ab − ac − bc) / 18on the raw bounds. When the bounds are large compared with their spread, those squares cancel away every significant digit.Triangular(1e9, 1e9+1, 1e9+2).Variancecame out as0. At1e12it came out negative, which madeStandardDeviationreturn NaN.Variancenow uses the widths the provider already stores:(lw² + uw² + lw·uw) / 18. The two forms are algebraically identical, but this one depends only on the triangle's shape and not on where it sits.Meanis nowMinimum + (lowerWidth + width) / 3, so bounds neardouble.MaxValueno longer overflow the sum.Tests
Triangular_Moments_Do_Not_Depend_On_Where_The_Triangle_Sits. It covers the three repro cases from the issue, the standard deviation at1e12, and a mean neardouble.MaxValue.1e9case: expected 0.1667, got 0). With the fix it passes.Essentials.Testssuite passes: 917/917.🤖 Generated with Claude Code
https://claude.ai/code/session_01VPis8BNX5ETFM2XytgJCz7
Generated by Claude Code