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Resource Requirements Config Group

Resource configuration in Resource Requirements config groups defines the CPU and memory requirements for a workload. These values enable the Altair SLC Hub server to calculate how many workloads can run concurrently across the available resources.

Defining Resource Requirements config groups can help to prevent workloads from running out of system resources. The configured values are used to estimate the resources a worker node requires to execute a workload. These values are checked at execution time and used to determine the worker node on which the workload will run.

Altair SLC Hub runs each workload on a single worker node. This may affect the number of workloads that can be run compared to the maximum theoretical limit based on total resource available in the Altair SLC Hub cluster.

Each workload is calculated in terms of memory and CPU requirement. The number of concurrent workloads is limited by either CPU requirement or memory requirement — whichever is exhausted first.

For example, an Altair SLC Hub installation is configured with two worker nodes:

  • Node1 has 32 GiB of memory and a 16 core CPU running at 2.5 GHz (2500 MHz).
  • Node2 has 256 GiB of memory and a 32 core CPU running at 2.5 GHz (2500 MHz).

Processing resource availability is calculated as number of cores multiplied by CPU speed:

  • Node1 has 40GHz processing resources (16* 2500 MHz) and 32 GiB memory.
  • Node2 has 80GHz processing resources (32* 2500 MHz) and 256 GiB memory.

If all workloads use the default resource requirements values, the maximum number of workloads that can be run concurrently in the cluster is 509, calculated as:

  • Node1 can concurrently execute 109 workloads, limited by Memory resource availability:
    • CPU: 40000 MHz ÷ 200 MHz = 200 workloads (maximum)
    • Memory 32 GiB ÷ 300 MB = 109 workloads (maximum).
  • Node2 can concurrently execute 400 workloads, limited by CPU resource availability:
    • CPU: 96000 MHz ÷ 200 MHz = 400 workloads (maximum)
    • Memory 256 GiB ÷ 300 MB = 873 workloads (maximum).

Note

Resource Requirements config group values are used for scheduling workloads and budgeting resources. They do not enforce hard resource limits during execution. This means that a workload can use more CPU or memory than the values specified in its Resource Requirements config group.

To help align runtime behaviour with the budgeted resources, define corresponding Altair SLC system options in the Altair SLC config group as part of the execution profile. For example, you can specify MEMSIZE to align Altair SLC memory usage with the configured memory requirement.

See Altair SLC Config Groups for more information.

Resources available for each worker node in the cluster is displayed in the Properties page for the worker node. You can access this page through the Cluster Nodes section of Hub Administration section of the portal.

Resource requirements and Altair SLC config groups are defined on the Execution Profiles page in the Hub Administration section of the portal.

Only one Resource Requirements config group can be active for an execution profile. The Budget CPU and Budget Memory values present on the Resources tab define the values of the Resource Requirements config group.

Resource Requirements config groups from previous installations have changed

In Altair SLC Hub version 2025.1 and earlier, it was possible to configure more than one Resource Requirement config group for an execution profile. When upgrading to a later version, these will be squashed into one Resource Requirement config group that represents the values that would have been applied previously in the legacy version.

Where multiple Altair SLC config groups are enabled in an execution profile, they are applied in the order they are listed. If more than one enabled config group affects the same system option, the final effective value depends on the order of the config groups and the merge type used for that option.

Once the workload has started execution, the total calculated resources available on the worker node are reduced by the configured amounts for the Resource Requirement config group.

Resource requirements default values

If no Resource Requirements config group has been specified in an execution profile, default values for CPU and memory are applied to a workload. The default values are:

  • 200 MHz CPU.
  • 300 MB memory.

These values provide a starting point that enables a reasonable number of workloads to run simultaneously on a worker node, while allowing enough system resources for a typical workload.

If required, values lower than the defaults can be specified for a Resource Requirements config group. The minimum values that can be specified for resource requirements are 1 MHz CPU and 10 MB memory. We do not, however, recommend setting values below the default values.