Posted in 2018

How do I log into the same login or pp node I used before

mistral.dkrz.de or mistralpp maps to a whole group of nodes to distribute the load. They all share the same file system so most of the time you do not have to care which node you are on. However, there are reasons why you may want to connect to a specific node. You first have to find out on which node you are. This may be indicated in your prompt or you can also use hostname for this purpose.

 In this case you are on login node 3. Connect to this node with

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Python Matplotlib fails with “QXcbConnection: Could not connect to display”

Matplotlib is useful for interactive 2D plotting and also for batch production of plots inside a job. The default behavior is to do interactive plotting which requires the package to open a window on your display. For this purpose you have to log into mistral with X11 forwarding enabled.

 If you run matplotlib in a jobscript where you just want to create files of your plots, you have to tell matplotlib to use a non-interactive backend. See matplotlib’s documentation how to do that and which backends are available. Here is how to select the Agg backend (raster graphics png) inside your script. Add to the top of your imports

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How can I avoid core files if my program crashes

Core files can be very helpful when debugging a problem but they also take a long time to get written for large parallel programs. This will limit the core size to zero, i.e. no core files are written:

Note that due to a bug in our current installation of the slurm scheduler, the option

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