specialized complex^real methods #24497
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stevengj
commented
Nov 7, 2017
| exp10(z::Complex) = exp10(float(z)) | ||
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| # _cpow helper function to avoid method ambiguity with ^(::Complex,::Real) | ||
| function _cpow(z::Complex{T}, p::Union{T,Complex{T}})::Complex{T} where T<:AbstractFloat | ||
| if p == 2 #square |
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Note that this p==2 special-case code dates all the way back to @jiahao in #2891, who I guess added it as a performance optimization?
The need for performance optimization for z^2 is probably mainly for literal powers, though, so maybe we should nowadays move this to a literal_pow method? For Complex64 and Complex128, z^2 is already inlined as z*z, but maybe you can save an operation or two by specializing it further.
ararslan
approved these changes
Nov 7, 2017
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This adds specialized methods for
complex^real, which would previously have first promoted tocomplex^complex. Fixes #14342.The performance improvement seems to be very small in typical cases (e.g. 6-8% for
Complex{Float64}^Float64), but it fixes a longstanding bug in the sign of the zero imaginary part for(2.0+0im)^-2.1and similar.