reduce allocations in dims_howmany

[jishnub]

This reduces some unnecessary allocations in dims_howmany. This may be reduced further by using StaticArrays, but that's a separate discussion as it'll increase the load time.

On master

julia> X = rand(100, 100);

julia> @btime FFTW.dims_howmany($X, $X, $(collect(size(X))), 1)
  689.000 ns (21 allocations: 1.59 KiB)
([100; 1; 1;;], [100; 100; 100;;])

This PR
Updated after e15a9b8

julia> @btime FFTW.dims_howmany($X, $X, size($X), 1);
  73.707 ns (2 allocations: 160 bytes)

[codecov]

Codecov Report

Patch coverage: 96.00% and project coverage change: +1.59 🎉

Comparison is base (82a99dc) 69.09% compared to head (270c27a) 70.68%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #269      +/-   ##
==========================================
+ Coverage   69.09%   70.68%   +1.59%     
==========================================
  Files           5        5              
  Lines         495      522      +27     
==========================================
+ Hits          342      369      +27     
  Misses        153      153              

Impacted Files	Coverage Δ
src/fft.jl	68.75% <96.00%> (+2.16%)	⬆️

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[stevengj]

Thanks, this is ancient code that needed a fresh look.

There's nothing StaticArrays can do that couldn't be done with tuples, perhaps with slightly more code, and I'd prefer to avoid the StaticArrays dependency.

[jishnub]

Thanks! I've updated it now, and all the unnecessary allocations are now avoided if region is an Int or a Tuple

[jishnub]

This should be ready now

[jishnub]

Gentle bump

[jishnub]

#266 should ideally have been v1.7.0 instead of v1.6.1 as it is mildly breaking, so I'm bumping the version in this PR instead.

[jishnub]

Gentle bump @stevengj

[stevengj]

LGTM