Nexus: DMC Step Simulation Files Not Generating after Successful Optimization Run #5845
Description
Describe the bug
I am using the Nexus workflow manager. I am trying to run a DMC calculation after an optimization. The optimization completes successfully with no output errors. However, Nexus will not produce the DMC simulation files after the optimization finishes. The Nexus job will just hang doing nothing, and I have to kill it. No error messages are produced. Using the skip_submit flag has does not change the outcome. There is no indication that memory is insufficient. Has someone seen this issue before?
To Reproduce
Steps to reproduce the behavior:
Nexus script, structure file, and optimization output file attached.
QMCPack version: 4.1.0.
Job submitted on an HPC. For 32 mpi threads, the job runs through the optimization runs in ~15 minutes. Hanging behavior can still will occur if I do a brief produce-files-only job run on the login node.
CPU version only.
Expected behavior
The dmc sim_* files should be generated, and Nexus should recognize when file generation is done.
System:
NDSU CCAST Prime Cluster. Other systems not tested.
Additional context
I have tested the legacy version, doing gcta as a metal or gap material, and not doing gcta, and all of these fail to make the dmc files generate. I have executed this workflow and DMC generates properly for the QMCPack 2025 Solids summer school example and for a custom Si Cubic model job. On an interesting note, when I commented out “twistnum=0” in the optimization, the dmc code will generate after optimization and then fail since multiple twists cannot be passed.
If any other information is needed, please let me know.