Thanks for separating this from PP-506
We’d like to see nfliter applied at the chunk level in the select statement. We certainly have jobs that require 2+ different types of nodes in a single job, so a job-wide nfilter would not suffice.
Chunk-level nfilter leads to the next complications (opportunities?), something I’ve pondered a bit as we’ve considered how to move toward an nfilter-like request mechanism. Here are a couple use cases I’m considering. I’ll use the resources_available resource “model” in my examples, at present model can be one of [san, ivy, has, bro] (representing Sandy Bridge, Ivy Bridge, Haswell, and Broadwell).
uc1) Multi-chunk job that chooses different MPI rank distributions per chunk based on memory, an example request might look like:
qsub -l select=1:mpiprocs=1:model=has:nfilter="node['resources_available'][‘mem’]>=512gb"+100:mpiprocs=12:nfilter="node['resources_available'][‘ncpus’]>=12 and node['resources_available'][‘gigs_per_core’]>=2gb"
uc2) Multi-chunk job that chooses different MPI rank distributions per chunk. The user doesn’t care which model is chosen, but they do want the same model to be chosen across all chunks. An example request might look like:
qsub -l select=1:mpiprocs=2:nfilter="node['resources_available'][‘model’]=pbs.same and bigmem=true"+100:mpiprocs=16:nfilter="node['resources_available'][‘model']=pbs.same and node['resources_available'][‘ncpus’]>=16"
In the above I’ve introduced a magic value pbs.same to accomplish the intent of the use case. I image another magic value pbs.any could satisfy a different use case where the user doesn’t care which model is provided by PBS. These values are illustrative, I’m not pushing for their use as presented here. The general notion is expressing an inter-chunk relationship. This is similar to the description of “like nodes” in the design of PP-506, but as I understand PP-506 a job-set would need to enumerate all requests that can satisfy the particular inter-chunk relationship rather than here where we constrain the matches a filter can come up with.
-Greg