Incorrect machine constant checks for Legendre recursion relations #106
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michael-petersen
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I've tested this; no issues on my end. Let's go ahead and merge!
michael-petersen
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Feb 7, 2025
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Summary
Previous version of the code used the minimum floating number not the minimum
epsilonsuch that1+epsilon != 1, which it should have used.Fix
Use additive machine constants from C++
limitsto set epsilon in Legendre functions on CPU and GPU. The assumption here is that both are use IEEE 754 standard for FP arithmetic. On the GPU side, the constant is set to float or double based on the value ofcuREALincudaUtil.cuH.Details
The gaff was discovered in positional quiet starts that happened to have
|cos(\theta)| = 1. This resulted ininffor Legendre function derivatives owing to divide by zero rather than cancellation. This has been rechecked with the fix enabled on the same previously failing ICs.