Computing time

Compute hour allocation

Each VACC service tier comes with a certain number of compute units (CUs). A CU is equivalent to using one CPU for one hour. When using GPUs, the rate is one CU per minute. Current allocations and CU definitions can be found on the Cost/Payment page.

Compute unit limits per tier as of 31 July 2025 were

Tier	CUs
1	250,000
2	3,000,000
3	> 3,000,000

In many cases, the Tier 1 allocation will be sufficient. You may consider increasing your tier if you will be running programs that use many CPUs and especially if you will be using GPUs extensively.

CU usage is evaluated twice yearly, and if it appears that an adjustment might be needed, the VACC administrator will contact you directly.

Monitoring your usage

We provide a script that will summarize your current CU usage, my_compute_usage. By default, it will report on the usage from one year prior to the date the program runs. An example of its default output is:

$ my_compute_usage 
Getting results from the Slurm job database.
This may take a moment...

CPU, GPU, and CU usage for the Slurm account pi-grundoon
for the period: 2024-07-31 to 2025-07-31

 ---------------------------Usage per User---------------------------------- 
   Account   |  Username  | CPU Hours used | GPU Hours used |    CUs used    
 pi-grundoon |  grundoon  |       90015.82 |           0.48 |         90044.90
 pi-grundoon |   albert   |       89971.59 |           0.00 |         89971.59

 ----------------------Usage total for Account------------------------------ 
   Account   |            | CPU Hours used | GPU Hours used |    CUs used    
 pi-grundoon |            |      179987.40 |           0.48 |        180016.49