[R] bizarre color space conversion problem

[Peter Langfelder]

Sarah, if you haven't done so already, please do us (OpenBLAS users) a
big favor and report the bug, either to Fedora or directly to OpenBLAS
maintainers.

Peter

On Thu, Jul 18, 2019 at 11:46 AM Sarah Goslee <sarah.goslee using gmail.com> wrote:
>
> Wow. You are entirely correct. I would not have been able to pinpoint
> the problem, or how to test it. Thank you.
>
> I am unhappy you are right, since these are the fast workstations I
> use for all of my heavy-duty analysis, and it's not even *possible* to
> rerun everything.
>
> Oh dear.
>
> Here, with the options you suggested, it produces the expected results:
>
> # env OPENBLAS_CORETYPE=Haswell R --vanilla
>
> > white <- c(x = 0.953205712549377, 1, y = 1.08538438164692)
> > red10.rgb <- structure(c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0), .Dim = c(10L, 3L), .Dimnames = list( NULL, c("r", "g", "b")))
> > convertColor(red10.rgb, from = "sRGB", to = "Lab")
>              L        a        b
>  [1,] 53.48418 80.01027 67.38407
>  [2,] 53.48418 80.01027 67.38407
>  [3,] 53.48418 80.01027 67.38407
>  [4,] 53.48418 80.01027 67.38407
>  [5,] 53.48418 80.01027 67.38407
>  [6,] 53.48418 80.01027 67.38407
>  [7,] 53.48418 80.01027 67.38407
>  [8,] 53.48418 80.01027 67.38407
>  [9,] 53.48418 80.01027 67.38407
> [10,] 53.48418 80.01027 67.38407
>
>
> > red10.rgb %*% as.list(environment(grDevices::colorspaces$sRGB$toXYZ))$M
>            [,1]      [,2]      [,3]
>  [1,] 0.4168213 0.2149235 0.0195385
>  [2,] 0.4168213 0.2149235 0.0195385
>  [3,] 0.4168213 0.2149235 0.0195385
>  [4,] 0.4168213 0.2149235 0.0195385
>  [5,] 0.4168213 0.2149235 0.0195385
>  [6,] 0.4168213 0.2149235 0.0195385
>  [7,] 0.4168213 0.2149235 0.0195385
>  [8,] 0.4168213 0.2149235 0.0195385
>  [9,] 0.4168213 0.2149235 0.0195385
> [10,] 0.4168213 0.2149235 0.0195385
>
> On Thu, Jul 18, 2019 at 1:59 PM Ivan Krylov <krylov.r00t using gmail.com> wrote:
> >
> > On Thu, 18 Jul 2019 13:30:09 -0400
> > Sarah Goslee <sarah.goslee using gmail.com> wrote:
> >
> > > I'm not even remotely a hardware expert: if the difference is due to
> > > changes in the instruction set, I assume that has potential
> > > consequences for other things, and I just happened to spot it in this
> > > particular case because it's visualization-based? (Yikes.)
> >
> > Yes, this might be bad. I have heard about OpenBLAS (specifically, the
> > matrix product routine) misbehaving on certain AVX-512 capable
> > processors, so much that they had to disable some optimizations in
> > 0.3.6 [*], which you already have installed. Still, would `env
> > OPENBLAS_CORETYPE=Haswell R --vanilla` give a better result?
> >
> > > As it says in my first email (but way at the bottom), I'd already
> > > gotten as far as locating the problem in this line from
> > > grDevices::convertColor()
> > >
> > >     xyz <- from$toXYZ(color, from.ref.white)
> >
> > Thanks for confirming this! It felt that I had to make sure, since the
> > behaviour we observe is so confusing.
> >
> > > > (red.xyz <- grDevices::colorspaces$sRGB$toXYZ(red.rgb,
> > > > white.point))[1,]
> > > [1] 0.7733981 0.9280769 0.1383974
> > > > # [1] 0.4168213 0.2149235 0.0195385
> >
> > One last check: would
> >
> > red.rgb %*% as.list(environment(grDevices::colorspaces$sRGB$toXYZ))$M
> >
> > still produce different results on your computers?
> >
> > > blas.x86_64                                 3.8.0-12.fc30
> > > openblas.x86_64                             0.3.6-2.fc30
> >
> > I do not know enough about Fedora's "alternatives" system, but it does
> > look like R is using OpenBLAS.
> >
> > > A: working
> > > Model name:          Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz
> >
> > > B: not working
> > > Model name:          Intel(R) Core(TM) i9-7900X CPU @ 3.30GHz
> >
> > Again, this points in the direction of OpenBLAS not doing AVX-512 math
> > properly. Let's hope that OPENBLAS_CORETYPE=Haswell solves it.
> >
> > --
> > Best regards,
> > Ivan
> >
> > [*]
> > https://github.com/xianyi/OpenBLAS/issues/1955
> > https://github.com/xianyi/OpenBLAS/issues/2029
> > https://github.com/xianyi/OpenBLAS/issues/2168
> > https://github.com/xianyi/OpenBLAS/issues/2182
>
>
>
> --
> Sarah Goslee (she/her)
> http://www.numberwright.com
>
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