Fix Student's T kernel formula sign error in tdist() - #593
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The tdist() function had a double-negative that caused strength to increase with distance instead of decrease: return max / pow(base, -(nu + 1.0) / 2.0); // wrong: dividing by negative exp Fixed to: return max * pow(base, -(nu + 1.0) / 2.0); // correct: multiply by negative exp This bug caused the Student's T spatial kernel to produce physically nonsensical results where interaction strength exceeded fmax at non-zero distances.
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Ack! Good catch. Inded: |
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This will also make it significantly faster, since multiplication is much faster than division. Maybe this is why you saw such a large speedup for Student's T in your benchmarking, @andrewkern! Your SIMD code was doing multiplication but the original code was (incorrectly) doing division? :-O |
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Fixes double-negative in exponent causing strength to increase with distance:
Closes #591
Also should resolve CI test failures in #592