Fw: Matplotlib 1.5.1 - Function pcolormesh throws Segmentation Fault / faulthandler traceback info / Error at Agg

Dear colleagues,

Complementing this topic:

. The segmentation fault error relates
to the use of the “Agg” graphical back-end which crashes with
larger plots when using the command pyplot savefig.
Case I switch to the .use(“Cairo”)
package, the processing completes OK although the image is not matching
the color scheme.
This machine, a z13, does not
have an interactive X display, its a cpu in a cloud, a back-end machine
with web access.

My question 1:
Is it possible to recompile the failing
“Agg” framework from its source in “c” and make it
compatible with the hardware. Any hints how to run the make
build and install and add it to the
Matplotlib pyplot services?

My question 2:
Is there an alternate back-end solution
available for .png or .tif, preferably in a Python space, that is accepted
by the matplotlib pyplot tool as
a valid choice and does not require
a display configuration? Worst case, is there a bypass solution available?

Thanks advance for your guidance.




Thanks for the quick feedback.

I’ve installed the “faulthandler”
package, added it to the import and enabled it with faulthandler.enable().

Below the console trace of the test
using the pcolormesh function and the traceback information:

python test3.py

Fatal Python error: Segmentation fault

Current thread 0x000003ffa45f7710 (most recent call first):
File "/usr/lib64/python2.7/site-packages/matplotlib/collections.py", line 1877 in draw
File "/usr/lib64/python2.7/site-packages/matplotlib/artist.py", line 61 in draw_wrapper
File "/usr/lib64/python2.7/site-packages/matplotlib/axes/_base.py", line 2324 in draw
File "/usr/lib64/python2.7/site-packages/matplotlib/artist.py", line 61 in draw_wrapper
File "/usr/lib64/python2.7/site-packages/matplotlib/figure.py", line 1159 in draw
File "/usr/lib64/python2.7/site-packages/matplotlib/artist.py", line 61 in draw_wrapper
File "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 474 in draw
File "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_agg.py", line 527 in print_png
File "/usr/lib64/python2.7/site-packages/matplotlib/backend_bases.py", line 2232 in print_figure
File "/usr/lib64/python2.7/site-packages/matplotlib/figure.py", line 1565 in savefig
File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line 688 in savefig
File "test3.py", line 47 in <module>
Segmentation fault

Hope this information helps to circle the

Claude Falbriard
Certified IT Specialist L2 - Middleware

**Phone:**55-13-99662-5703 | Mobile:55-13-98117-3316E-mail: claudef@…4510…9…

Benjamin Root <ben.v.root@…287…>
Claude Falbriard/Brazil/IBM@…4709…
Matplotlib Users matplotlib-users@lists.sourceforge.net
24/02/2016 17:35
Re: [Matplotlib-users]
Matplotlib 1.5.1 - Function pcolormesh throws Segmentation Fault

Sorry, forgot to post the link: https://pypi.python.org/pypi/faulthandler/
On Wed, Feb 24, 2016 at 3:33 PM, Benjamin Root <ben.v.root@…287…> wrote:
Could you try using faulthandler and post the traceback
please? That’ll help us isolate the problem better.
Ben Root
On Wed, Feb 24, 2016 at 3:04 PM, Claude Falbriard <claudef@…3779…> wrote:
Dear colleagues,
I’ve done a build from source of latest Matplotlib package
and deployed it at our IBM z13 machine (s390x). It uses the current release
During the unit tests I found an issue with a test case from NOAA which
uses a pcolormesh draw function with basemap.
Example 2: Plot data from an NWW3 GRiB2 file - [ here: http://polar.ncep.noaa.gov/waves/examples/usingpython.shtml]
The following line is causing a Segmentation fault error even when
adding an 8GB swap memory to the process:
cs = m.pcolormesh(x,y,data,shading='flat',cmap=plt.cm.jet)

I also tryed to execute other, similar samples that use pcolormesh, but
receiving the same error. Is this a known issue or might it be be related

to the memory environment ? Any hints how to debug this error?
Claude Falbriard
Certified IT Specialist L2 - Middleware

**Phone:**55-13-99662-5703| Mobile:55-13-98117-3316E-mail: claudef@…3779…

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