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.

As an example, consider a job running on two nodes of the default partition on Genius, where TRESBillingWeights=CPU=4.62963 applies:

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

If this job finishes in 2.5 hours (i.e., walltime is 150 minutes), the user will be charged:

floor(4.62963 * (2 * 36)) * 150 = 49 950 credits

You can also get such estimates from the sam-quote tool by providing it with your job submission command:

$ sam-quote sbatch --account=lp_myproject --clusters=genius --nodes=2 \
                   --ntasks-per-node=36 --time=2:30:00 myjobscript.slurm
49950

Note that sam-quote assumes a worst-case scenario in which the job does not stop before reaching its time limit.

Charge rates#

The table below shows the charge rates for each CPU and GPU type on Genius and wICE. These values correspond to the number of Slurm credits needed to allocate one core or GPU during one minute.

Cluster

Resource

Type

TRESBillingWeights

Genius

Skylake

CPU core

4.62963

Skylake (bigmem)

CPU core

5.55556

Skylake (superdome)

CPU core

18.7500

Cascadelake

CPU core

4.62963

P100

GPU

41.6667

V100

GPU

59.5833

wICE

Icelake

CPU core

2.54630

Icelake (bigmem)

CPU core

4.39815

Icelake (hugemem)

CPU core

4.39815

Sapphire Rapids

CPU core

3.47222

Zen4 Genoa

CPU core

3.47222

A100

GPU

141.667

H100

GPU

569.444