Increase Delaunator orient function robustness #479
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## main #479 +/- ##
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Coverage 90.85% 90.85%
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Files 91 91
Lines 6406 6406
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Hits 5820 5820
Misses 586 586 Continue to review full report in Codecov by Sentry.
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…ween release and debug mode.
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I found a corner case where in debug mode where the Delaunator orient function return a different result depending on whether it is in debug or release mode. This causes issues in the release mode, which is basically wrong. The issue comes down to that
(qy - py) * (rx - qx) - (qx - px) * (ry - qy)is exactly zero in debug mode (so(qy - py) * (rx - qx) - (qx - px) * (ry - qy) < 0.0is false) and the release mode is slightly less accurate and results in -3.48086e-21, which then returns true.The solution I have gone for here is to check if the value is smaller that -epsilon. I guess it is not a perfect solution, but it seems to solve the problem.
For reference, these are the values of
(qy - py) * (rx - qx) - (qx - px) * (ry - qy)and the results for debug mode left and release mode right.(0.80218-0.793353) * (-1.78205 - -1.7908) - (-1.7908 - -1.79954) * (0.811008 - 0.80218) = 0 | (0.80218-0.793353) * (-1.78205 - -1.7908) - (-1.7908 - -1.79954) * (0.811008 - 0.80218) = -3.48086e-21Playing with some of the flag could potentially help, but I just want it to be more robust, which this pull request achieves.