Walltime is not queue wait.
Walltime is the longest your job may run once it starts. If it runs longer, PBS stops it. Queue wait is the separate delay before it starts, and nothing on this page can predict it.
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Measure a small representative run
Time how long startup takes and how long each record (frame, sample, file) takes to process.
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Add headroom
Runs vary. 25% extra is a common starting point; use more if your measurements were noisy.
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Check it fits the queue’s limit
If it doesn’t, split the work into smaller jobs or use a checkpoint your program actually supports.
Estimate your request.
Estimate a walltime request
Uses startup + records × processing time + finalization, then applies headroom. It cannot predict queue wait or account for non-linear scaling.
Example: 60 minutes of work + 25% headroom → 01:15:00. Queue wait is unknown.
Put it in your job script.
Use the HH:MM:SS value in a #PBS line, for
example:
#PBS -l walltime=01:15:00Check queue limits before submitting. On 28 September 2026 the QCR route allowed up to 48 hours, but limits change. See choosing resources and the queue and walltime reference.