Use Julia 1.6's new reinterpretarray machinery

[timholy]

When available, this switches to using Julia 1.6's new reinterpret(reshape, T, A) for our colorview/channelview functionality. As documented in #142, this essentially puts to rest the performance problems we've had since Julia 1.0 with ReinterpretArray.

The tests will still not quite pass on nightly due to show failures, but I plan to fix that in a separate PR.

Closes #142

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@d9dccd9). Click here to learn what that means.
The diff coverage is 71.42%.

@@            Coverage Diff            @@
##             master     #145   +/-   ##
=========================================
  Coverage          ?   74.41%           
=========================================
  Files             ?       10           
  Lines             ?      516           
  Branches          ?        0           
=========================================
  Hits              ?      384           
  Misses            ?      132           
  Partials          ?        0           

Impacted Files	Coverage Δ
src/ImageCore.jl	70.37% <ø> (ø)
src/colorchannels.jl	43.57% <45.45%> (ø)
src/convert_reinterpret.jl	85.36% <80.64%> (ø)

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[timholy]

So, it seems that our benchmarks don't run anymore as part of CI. Intended? I see #123.

I should also acknowledge that because I've tightened the "bounds" on what we consider acceptable, include("benchmarks.jl") is pretty noisy on 1.5:

julia> include("benchmarks.jl")
[ Info: Benchmark tests are warnings for now
┌ Warning: colorview2: failed on mysum_elt_boundscheck with eltype Float32, time ratio 8.859957776213934, tol 5
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138
┌ Warning: colorview2: failed on mysum_elt_inbounds with eltype Float32, time ratio 8.861587413823582, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138
┌ Warning: channelview1: failed on mysum_index_inbounds_simd with eltype Float32, time ratio 27.78320479862896, tol 20
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:119
┌ Warning: colorview2: failed on mysum_index_inbounds_simd with eltype Float32, time ratio 6.7447698744769875, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138
┌ Warning: colorview1: failed on myfill1! with eltype Float32, time ratio 11.369456762188495, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:132
┌ Warning: colorview2: failed on myfill1! with eltype Float32, time ratio 18.31693755262115, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138
┌ Warning: channelview1: failed on myfill2! with eltype Float32, time ratio 29.777311566200062, tol 20
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:119
┌ Warning: colorview1: failed on myfill2! with eltype Float32, time ratio 13.63551190747891, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:132
┌ Warning: colorview2: failed on myfill2! with eltype Float32, time ratio 12.960752632917918, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138
┌ Warning: colorview2: failed on mysum_elt_boundscheck with eltype Float64, time ratio 7.129490249743414, tol 5
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138
┌ Warning: colorview2: failed on mysum_elt_inbounds with eltype Float64, time ratio 7.149125814192664, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138
┌ Warning: colorview1: failed on myfill1! with eltype Float64, time ratio 7.043604325936975, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:132
┌ Warning: colorview2: failed on myfill1! with eltype Float64, time ratio 9.796395232297128, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138
┌ Warning: colorview1: failed on myfill2! with eltype Float64, time ratio 6.146765267631468, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:132
┌ Warning: colorview2: failed on myfill2! with eltype Float64, time ratio 9.315949234411704, tol 3
└ @ Main ~/.julia/dev/ImageCore/test/benchmarks.jl:138

but on 1.6 I get

julia> include("benchmarks.jl")
[ Info: Benchmark tests are warnings for now

julia>

[johnnychen94]

I'm a little unsure what to benchmark so #123 is probably abandoned. The noise you mentioned is also concerning that I failed to restart that...

FYI, https://github.com/JuliaImages/ImageContrastAdjustment.jl has a well-running benchmark CI that you can use to get some idea.

[timholy]

For now, though, should we still be running the benchmarks? I'm guessing that in

ImageCore.jl/test/runtests.jl

Lines 32 to 37 in d9dccd9

	# run these last
	isCI = haskey(ENV, "CI") || get(ENV, "JULIA_PKGEVAL", false)
	if Base.JLOptions().can_inline == 1 && !isCI
	@info "running benchmarks"
	include("benchmarks.jl") # these fail if inlining is off
	end

"CI" isn't set by GitHub Actions?

EDIT: oh wait, we specifically don't run them on CI. Can you remind me why?
EDIT2: nvm, see #12 and specifically 623052b. I don't know why, maybe Travis was too noisy? Should we try again with GitHub Actions?

[johnnychen94]

One drawback of setting up benchmarkCI is that we hand almost everything to PkgBenchmark and so we can't do

t_baseline = @belapsed f_baseline(...)
t = @belapsed f(...)
ratio = t/t_baseline

we might need two benchmark CIs for the very different two benchmark tasks:

• master branch vs PR branch (using BenchmarkCI)
• baseline indexing vs reinterpret indexing (set up our own version from test/benchmark.jl)

[timholy]

Gotcha. Seems complicated enough that we should just accept the status quo here and deal with it separately.

I'll leave this open for a bit for review, in case there are any concerns.