Not so much about the source, but in the sbatch documentation [1], I think the --begin and --nodes parameters might interact. And yes, this is semi-educated speculation on my part.

From the nodes= section, “The job will be allocated as many nodes as possible within the range specified and without delaying the initiation of the job.” So without specifying a begin time, the scheduler will look for the first available time it can schedule the minimum number of nodes requested. If it can find more nodes, up to the maximum requested, then you’d get a higher number of nodes at that time.

[1] https://slurm.schedmd.com/sbatch.html

From: Declan Valters via slurm-users <slurm-users@lists.schedmd.com>
Date: Tuesday, October 8, 2024 at 10:36 AM
To: slurm-users@lists.schedmd.com <slurm-users@lists.schedmd.com>
Subject: [slurm-users] How does --nodes=min[-max] determine number of nodes to allocate?

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Hi,

I am trying to understand how Slurm determines the actual number of nodes to allocate to a job specified with –nodes=min[-max]

I’ve been trying to follow the source code through on Github – could anyone point me in the right area(s)/source files/functions to look at to understand the program logic behind this.

Many thanks in advance,

Declan

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