On Phoenix, the default number of CPUs assigned to jobs requesting an Nvidia Tensor Core A100 GPU has recently changed. Now, jobs requesting one or more A100 GPUs will be assigned 8 cores per GPU by default, rather than 32 cores per GPU. You may still request up to 32 cores per GPU if you wish by using the --ntasks-per-node flag in your SBATCH script or salloc command to specify the number of CPUs per node your job requires. Any request with a CPU:GPU ratio of at most 32 will be honored.
12 of our Phoenix A100 nodes host 2 GPUs and 64 CPUs (AMD Epyc 7513), supporting a CPU:GPU ratio up to 32, and can be allocated through both the inferno (default priority) and embers (free backfill) QOSs. We have recently added 1 more A100 node with 8 GPUs and 64 CPUs (AMD Epyc 7543), requiring this change to the default ratio. This new node is available only to jobs using the embers QOS due to the funding for its purchase.
Please visit our documentation to learn more about GPU requests and QOS or about compute resources on Phoenix and contact us with any questions about this change.