add logabstanh
#86
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add logabstanh
#86
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devmotion
reviewed
Nov 16, 2024
devmotion
reviewed
Nov 16, 2024
src/basicfuns.jl
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| The implementation ensures `logabstanh(-x) = logabstanh(x)`. | ||
| """ | ||
| function logabstanh(x::Real) | ||
| return log1p(-2/((exp(2abs(x))+1))) |
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As indicated by the special cases close to 0 for Float32 and Float64, maybe a safer default would be
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| return log1p(-2/((exp(2abs(x))+1))) | |
| return log(abs(tanh(x))) |
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I think the version I wrote stays more accurate overall but I'll do a test
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I don't think it's possible to do such an analysis? You can't realistically test any subtype of Real.
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for any AbstractFloat log(tanh(x)) will be inaccurate for large x since tanh(x) will be very close to 1.
Co-authored-by: David Widmann <devmotion@users.noreply.github.com>
Co-authored-by: David Widmann <devmotion@users.noreply.github.com>
Co-authored-by: David Widmann <devmotion@users.noreply.github.com>
Co-authored-by: David Widmann <devmotion@users.noreply.github.com>
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as requested by @c05 on slack. This has 15 ULP for Float64, and 5 ULP for Float32.