Credits to use KU Leuven infrastructure#

KU Leuven uses a credit system to do accounting on the Tier-2 HPC systems it hosts.

How do I request credits on the KU Leuven Tier-2 systems#

KU Leuven users#

You can request two types of job credits: introduction credits and project credits.

Introduction credits

This is a limited amount of free credits for test and development purposes.

Project credits

These are job credits used for actual research and production runs.

You will find the relevant information to apply for both types of credits, including pricing, in the Service Catalog (login required).

UHasselt users#

If you would like credits for a new project, please fill out the credit request form.

Warning

Please read and follow the instructions in that form carefully!

If you require additional credits for an existing project, please contact your VSC coordinator Geert Jan Bex.

Other users#

Please contact your VSC coordinator/contact or your local support staff.

Job cost calculation#

On Tier-2 clusters, we use Slurm for accounting purposes (on top of resource and job management). See Slurm accounting page for additional information. In Slurm terminology, the cost of a job depends on the trackable resources (TRES) it consumes. Two distinct TRES are the number of CPU cores and GPU devices. Different types of CPU and GPU nodes are given different weights (TRESBillingWeights) which you can retrieve as follows for e.g. wICE:

scontrol show partitions --clusters=wice

As an example, for a GPU node, the weights are configured as:

TRESBillingWeights=CPU=2.546296296,GRES/gpu:a100-sxm4-80gb=141.6666667,GRES/shard:a100-sxm4-80gb=141.6666667

CPU-only jobs

The following formula applies:

CPU TRESBillingWeights * num_cores * walltime

Where

  • CPU TRESBillingWeights is the applied weight for CPU resources (see above)

  • num_cores is the effective number of cores used for the job

  • walltime is the number of minutes that the job ran

GPU jobs

The following formula applies:

(CPU TRESBillingWeights * num_cores + GPU TRESBillingWeights * num_gpus) * walltime

Where

  • CPU TRESBillingWeights is the applied weight for CPU resources (see above)

  • GPU TRESBillingWeights is the applied weight for GPU resources (see above)

  • num_cores is the effective number of cores used for the job

  • num_gpus is the number of GPUs requested for the job

  • walltime is the number of minutes that the job ran

Note

Effective number of cores is not necessarily equal to what the user requests. E.g. if a job requests a single core/task, but the full memory of a node on wICE, then one node is blocked for such a job. Consequently, the effective number of cores will be 72, instead of 1.

Note

The Tier-2 cluster has several types of compute nodes. Hence, different TRESBillingWeights apply to different resources on different partitions of Genius and wICE. The difference in cost between different machines/processors reflects the performance difference between those types of nodes. For additional information, you may refer to the HPC Service Catalog (login required).

The difference in cost between different machines/processors reflects the price-performance difference between those types of nodes. The total cost of a job will be comparable on any compute node, but the walltime will be different, depending on the performance of the nodes.

In the examples below, you run your jobs on a skylake node, for which we charge 10 000 Slurm credits per hour.

An example of a job running on multiple nodes and cores is given below:

$ sbatch --account=lp_astrophysics_014 --clusters=genius --nodes=2 \
         --ntasks-per-node=36 simulation_3415.slurm

For Genius thin nodes we have TRESBillingWeights=CPU=4.62963. If this job finishes in 2.5 hours (i.e., walltime is 150 minutes), the user will be charged:

4.62963 * (2 * 36) * 150 = 50 000 credits

Charge rates#

The charge rate for the various node types of Genius and wICE are listed in the table below. The reported cost is the number of Slurm credits needed per core/GPU per minute.

Cluster

node type

TRESBillingWeights

Genius

skylake

4.62963

cascadelake

4.62963

skylake bigmem

5.55556

Nvidia P100 GPU

41.6667

Nvidia V100 GPU

59.5833

Superdome

18.7500

wICE

icelake

2.54630

icelake bigmem

4.39815

Nvidia A100 GPU

141.667

How do I get credits to use the Tier-1 infrastructure#

Access to the Tier-1 is project-based, if you have a starting grant or an approved project, or you pay for your compute time, you should have received information on your job credits. If not, please refer to the official VSC website, or contact your VSC support team.