Quiver barb size not correct on some arches (ppc64, ppc64le...) #7797

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AdamWill opened this Issue Jan 11, 2017 · 10 comments

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@AdamWill
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Continuing to work through test suite failures found when building on the Fedora ppc64 arch (big-endian) but not on little-endian arches. Two failures:

matplotlib.tests.test_quiver.test_barbs.test
matplotlib.tests.test_transforms.test_pre_transform_plotting.test

seem to be caused by differences in the lengths of 'barbs' on 'quivers' - the former is a test specific to such barbs, the latter includes a figure with some barbs as part of a larger test. In both cases, the lengths of the barbs come out subtly differently on ppc64:

barbs_test_image GOT: barbs_test_image
barbs_test_image EXPECTED: barbs_test_image-expected
pre_transform_data GOT: pre_transform_data
pre_transform_data EXPECTED: pre_transform_data-expected

the difference is quite subtle, it helps to A/B the images quickly in an image viewer. AFAICS, in all cases where the lengths are visibly different, the barbs actually produced are slightly shorter than expected.

@AdamWill
Contributor
@AdamWill
Contributor

This may be #4385 ?

@AdamWill AdamWill changed the title from Quiver barb size not correct on ppc64 (big-endian) to Quiver barb size not correct on some arches (ppc64, ppc64le...) Jan 11, 2017
@AdamWill
Contributor

This also affects ppc64le, so it's not a big-endian thing. It may also affect aarch64.

@dopplershift
Contributor

I don't think #4385--that's a different rounding problem, IMO. It looks like some kind of pixel snapping issue to me.

I don't have a clue how to begin to figure out what's going on here without access to a machine...

@AdamWill
Contributor

@puiterwijk ahoy! would you be willing to let an upstream matplotlib person have access to one of our sandbox ppc64 or aarch64 environments to try and look into this kinda thing?

@puiterwijk

@AdamWill You can add their key to your test instance, and let them use that?

@AdamWill
Contributor

I thought you'd already torn it down :) If you don't mind leaving it up a while longer, sure. @dopplershift , can you send me your ssh pubkey?

@dopplershift
Contributor

Sorry, I've been swamped with conference prep. It will probably be no earlier than the 21st/22nd that I might be able to get to this. Not sure if that time frame works for you guys.

@AdamWill
Contributor

I don't think it should be a problem, we should still be able to put up an instance for you at that time, I think.

@puiterwijk

@AdamWill I'll keep your current instance around. Just let me know when I can clear it after they're done with it.

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