Neither nprocs, -np, or PYMAPDL_NPROC override SLURM env variable core count - PySyC workflow #4160
Description
🤓 Before submitting the issue
- I have visited the Troubleshooting section.
- I have searched among the existing issues.
- I am using a Python virtual environment.
- I am using the latest version of PyMAPDL and its dependencies (fully updated virtual environment). You can update them using
pip install --upgrade --upgrade-strategy eager ansys-mapdl-corein your activated virtual environment.
🔍 Description of the bug
I am following this method of submission via submission script:
https://mapdl.docs.pyansys.com/version/stable/user_guide/hpc/pymapdl.html
So SLURM reserves 32 cores on 1 node. 32 cores are then given to Fluent and to MAPDL.
I want to reduce the MAPDL cores to 16. For this I try both 1 or 2 as follows:
- My python script launches MAPDL using:
mechanical = pymapdl.launch_mapdl(nproc = 16)
- I put PYMAPDL_NPROCS=16 in my submission script and in python script either:
a. mechanical = pymapdl.launch_mapdl()
b. not issue this at all and wait for pysyc to launch mapdl (which it does)
In all cases MAPDL launches on 32 cores.
🕵️ Steps To Reproduce
import ansys.fluent.core as pyfluent
import ansys.mapdl.core as pymapdl
import ansys.systemcoupling.core as pysystemcoupling
Fluent_folder = "Fluent_1"
Fluent_case = "Fluent-overset-laminar.cas.h5"
Fluent_cores = 32
Fluent_ui_mode = "no_gui" # -gu
Mechanical_folder = "Mechanical_2"
Mechanical_jobname = "Mechanical"
Mechanical_input = "Mechanical.dat"
Mechanical_scp = "Mechanical_2/Mechanical.scp"
Mechanical_cores = 16
mechanical = pymapdl.launch_mapdl()
#mechanical = pymapdl.launch_mapdl(nproc = Mechanical_cores,override = True)
fluent = pyfluent.launch_fluent(case_file_name = Fluent_case, processor_count = Fluent_cores, ui_mode = Fluent_ui_mode, cwd = Fluent_folder, graphics_driver = "null")
syc = pysystemcoupling.launch(start_output=True)
solid = syc.setup.add_participant(input_file = Mechanical_scp)
fluid = syc.setup.add_participant(participant_session = fluent)
fsi_interface = syc.setup.add_interface(
side_one_participant=solid,side_one_regions=['FSIN_1'],
side_two_participant=fluid,side_two_regions=['fsi'])
force_transfer_name = syc.setup.add_data_transfer(
interface=fsi_interface,
target_side="One",
target_variable="FORC",
source_variable="force",
)
displacement_transfer_name = syc.setup.add_data_transfer(
interface=fsi_interface,
target_side="Two",
source_variable="INCD",
target_variable="displacement",
)
syc.setup.solution_control.time_step_size = 1e-3
syc.setup.solution_control.end_time = 1e-3
syc.setup.solution_control.maximum_iterations = 1
syc.solution.solve()
syc.solution.shutdown()
syc.exit()
💻 Which Operating System are you using?
Linux
🐍 Which Python version are you using?
3.10
💾 Which MAPDL version are you using?
25R1
📝 PyMAPDL Report
PyAnsys Software and Environment Report
Date: Thu Aug 07 12:41:15 2025 CEST
OS : Linux (Rocky Linux 8.10)
CPU(s) : 32
Machine : x86_64
Architecture : 64bit
RAM : 187.5 GiB
Environment : Python
File system : xfs
GPU Vendor : Mesa
GPU Renderer : llvmpipe (LLVM 17.0.2, 256 bits)
GPU Version : 4.5 (Core Profile) Mesa 23.1.4
Python 3.10.12 (main, Mar 26 2024, 02:17:48) [GCC 8.2.0]
ansys.mapdl.core : 0.70.2
numpy : 1.26.4
platformdirs : 4.3.7
scipy : 1.15.2
grpc : 1.71.0
ansys.api.mapdl.v0 : Version unknown
ansys.mapdl.reader : 0.54.2
google.protobuf : 4.25.6
ansys-math-core : 0.2.2
matplotlib : 3.10.1
pyvista : 0.45.0
pyiges : 0.3.1
tqdm : 4.67.1
ansys-tools-visualization_interface : 0.9.1
pandas : 2.2.3
ansys_sphinx_theme : Module not found
ansys.acp.core : Module not found
ansys.dpf.composites : Module not found
ansys.dpf.core : Module not found
ansys.dpf.post : Module not found
ansys.fluent.core : 0.30.2
ansys.fluent.visualization : Module not found
ansys.fluent.parametric : Module not found
ansys.geometry.core : Module not found
ansys.hps.client : Module not found
ansys.math.core : 0.2.2
ansys.mechanical.core : Module not found
ansys.meshing.prime : Module not found
ansys.modelcenter.workflow : Module not found
ansys.motorcad.core : Module not found
ansys.openapi.common : Module not found
ansys.optislang.core : Module not found
ansys.platform.instancemanagement : 1.1.2
ansys.pyensight.core : Module not found
ansys.rocky.core : Module not found
ansys.seascape : Module not found
ansys.simai.core : Module not found
ansys.systemcoupling.core : 0.9.0
ansys.turbogrid.core : Module not found
ansys.tools.report : 0.8.2
ansys.tools.versioning : 0.6.0
pyaedt : Module not found
pyedb : Module not found
pygranta : Module not found
pytwin : Module not found
appdirs : 1.4.4
pexpect : 4.9.0
Ansys Environment Report
Ansys Installation
No Ansys installations provided
Ansys Environment Variables
PYMAPDL_NPROC 16
PYMAPDL_MAPDL_EXEC /home/pshutche/ansys_inc/v251/ansys/bin/ansys251
ANSYSLI_SERVERS 2325@ottvmlicense1:2325@ottlicense6
FLUENT_MAX_IDLE_TIMEOUT 1440
ANSYSLMD_LICENSE_FILE 1055@ottvmlicense1:1055@ottlicense6
FLUENT_WEBSERVER_TOKEN pshutche
AWP_ROOT251 /home/pshutche/ansys_inc/v251
📝 Logger output file
Show the logger output file.
# PASTE HERE THE CONTENT OF THE LOGGER OUTPUT FILE.