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Servers

There are servers at DIKU that are accessed through various esoteric mechanisms. You might need to talk to various people to get access, but once you have access, this is how you connect and use them.

The DIKU cluster

Also known as Hendrix or the IMAGE cluster. See here for access and other useful information.

Tips and tricks

  • Remember that this is a shared system with many users. Don't do clearly antisocial things. For example, don't leave an interactive job idle for a long period of time on an in-demand node while you go for lunch.

  • To run a command on an arbitrary node with an arbitrary GPU:

    srun --gres=gpu:1 --pty nvidia-smi

  • To get a an interactive session on an arbitrary node:

    srun --pty bash

  • To get an interactive session on a node with an arbitrary GPU:

    srun --gres=gpu:1 --pty bash

  • To get an interactive session on a node with a specific GPU:

    srun -p gpu --gres=gpu:titanx:1 --pty bash

    See this table for available GPUs. (Note that the table may not contain correct names - try lowercase versions of the indicated names.)

  • To start an interactive session on a specific node:

    srun -p gpu -w hendrixgpu03fl --pty bash

    Note that you will also need to add an appropriate --gres to access the GPU(s) if you need them.

  • To see all available resources and which nodes have them:

    sinfo -o "%60N  %5c  %10m  %20G "

  • You can add --exclusive to srun to get an entire node to yourself, but you may be waiting a long time. Otherwise you will only have exclusive access to the resources you asked for (e.g. you may get the GPU to yourself, but someone else may be hammering the CPU cores).

  • You may want to add --time=00:20:00 to srun, which will allow your command to run before jobs that demand infinite execution time...

Compiling Haskell

  • Use module load gmp to make the GMP library available. GHC usually expects this to be available. Some SML compilers do, too.

  • Use ghcup to install GHC and cabal. You may need to use the following command to obtain a working GHC:

    $ ghcup install ghc --set -p x86_64-fedora27-linux

  • Compilation with cabal is likely to make progress and then fail with errors such as:

    /home/.../dist-newstyle/tmp/package-registration--811774
removeDirectoryRecursive:removeContentsRecursive:removeDirectory: unsatisfied
constraints (Directory not empty)

    As far as I can determine, this is due to the network filesystem not following POSIX semantics. However, this error is nondeterministic and cabal will make a bit of progress every time, so just keep retrying until it is done.

Adding modules

The system has a standard HPC module system. Use it with e.g. module load cuda. The set of available modules is maintained by KU IT, and you can request more modules by opening a ticket at https://serviceportal.ku.dk under Forsknings-IT -> Forskningsapplikationer og Service -> Rådgivning og support. They seem pretty responsive.

Futhark servers

The DIKU cluster has three so-called "Futhark servers" that are not properly hooked into the Slurm queue system. They have the following hostnames:

  • hendrixfut01fl
  • hendrixfut02fl
  • hendrixfut03fl

You access them by SSH'ing into the Hendrix gateway server and then SSH'ing into one of the hosts listed above, provided you have permission (see below). From there, you can run normal Unix commands. The module system is available, but Slurm is not.

Granting permission

To access the Futhark servers, you must be added to the SRV-hendrixfut-users group on identity.ku.dk.