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Subject: |
python-matplotlib fails to build on i686-linux |
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Date: |
Fri, 03 Apr 2020 17:20:08 +0200 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) |
Hi Guix,
The package python-matplotlib fails to build during the check phase on
i686-linux. The test failure appears to be deterministic:
--8<---------------cut here---------------start------------->8---
=================================== FAILURES ===================================
_______________________ test_slider_horizontal_vertical ________________________
def test_slider_horizontal_vertical():
fig, ax = plt.subplots()
slider = widgets.Slider(ax=ax, label='', valmin=0, valmax=24,
valinit=12, orientation='horizontal')
slider.set_val(10)
assert slider.val == 10
# check the dimension of the slider patch in axes units
box = slider.poly.get_extents().transformed(ax.transAxes.inverted())
> assert_allclose(box.bounds, [0, 0, 10/24, 1])
E AssertionError:
E Not equal to tolerance rtol=1e-07, atol=0
E
E Mismatch: 25%
E Max absolute difference: 1.11022302e-16
E Max relative difference: 2.66453526e-16
E x: array([ 0.000000e+00, -2.310706e-18, 4.166667e-01, 1.000000e+00])
E y: array([0. , 0. , 0.416667, 1. ])
/gnu/store/8g8yfikj63wf0y3hwvpk00hqj5wpfs7v-python-matplotlib-3.1.2/lib/python3.7/site-packages/matplotlib/tests/test_widgets.py:333:
AssertionError
--8<---------------cut here---------------end--------------->8---
Im currently on commit 151f3d4.
Regards,
Diego
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--- Begin Message ---
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Subject: |
Re: bug#40406: python-matplotlib fails to build on i686-linux |
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Date: |
Sat, 14 Nov 2020 22:14:08 -0500 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) |
Hello Diego,
Diego Nicola Barbato <dnbarbato@posteo.de> writes:
> Hey,
>
> Diego Nicola Barbato <dnbarbato@posteo.de> writes:
>
> [...]
>
>> Apparently there is nothing wrong with the slider. Instead matrix
>> multiplication, which is used under the hood for transformations, seems
>> to sometimes produce incorrect results on i686-linux. I have reported
>> this as a separate bug (https://debbugs.gnu.org/41665).
>
> I got this wrong: This issue isn't caused by the Numpy bug, since
> Matplotlib doesn't use Numpy for transformations. Both bugs are caused
> by the excess precision of the x87 FPU's floating point registers.
>
> I've attached a patch which makes sure that the C and C++ extensions are
> compiled with -ffloat-store. This doesn't get rid of all possible
> rounding errors but it's enough for the slider test to pass.
Thanks for the investigationd and workaround! I've tested it and it
seems to work well. I've pushed a slightly modified version to master
as commit 81643c4cf3e61f5a98b92a72a92c230f5e7ca905.
Thank you!
Closing.
Maxim
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