feat: adding 'pymapdl_nproc' to non-slurm runs (#3487)

* feat: adding 'pymapdl_proc' to non-slurm run. Adding tests too.

* chore: adding changelog file 3487.miscellaneous.md [dependabot-skip]

---------

Co-authored-by: pyansys-ci-bot <[email protected]>

doc/changelog.d/3487.miscellaneous.md

@@ -0,0 +1 @@
+feat: adding 'pymapdl_nproc' to non-slurm runs

src/ansys/mapdl/core/launcher.py

@@ -2330,20 +2330,24 @@ def get_cpus(args: Dict[str, Any]):
 
     # Bypassing number of processors checks because VDI/VNC might have
     # different number of processors than the cluster compute nodes.
+    # Also the CPUs are set in `get_slurm_options`
     if args["ON_SLURM"]:
         return
 
     # Setting number of processors
     machine_cores = psutil.cpu_count(logical=False)
 
+    # Some machines only have 1 core
+    min_cpus = machine_cores if machine_cores < 2 else 2
+
     if not args["nproc"]:
-        # Some machines only have 1 core
-        args["nproc"] = machine_cores if machine_cores < 2 else 2
-    else:
-        if machine_cores < int(args["nproc"]):
-            raise NotEnoughResources(
-                f"The machine has {machine_cores} cores. PyMAPDL is asking for {args['nproc']} cores."
-            )
+        # Check the env var `PYMAPDL_NPROC`
+        args["nproc"] = int(os.environ.get("PYMAPDL_NPROC", min_cpus))
+
+    if machine_cores < int(args["nproc"]):
+        raise NotEnoughResources(
+            f"The machine has {machine_cores} cores. PyMAPDL is asking for {args['nproc']} cores."
+        )
 
 
 def remove_err_files(run_location, jobname):

tests/test_launcher.py

@@ -44,6 +44,7 @@
     force_smp_in_student,
     generate_mapdl_launch_command,
     generate_start_parameters,
+    get_cpus,
     get_exec_file,
     get_run_location,
     get_slurm_options,
@@ -1112,3 +1113,35 @@ def test_launch_grpc(tmpdir):
     assert isinstance(kwags["stdin"], type(subprocess.DEVNULL))
     assert isinstance(kwags["stdout"], type(subprocess.PIPE))
     assert isinstance(kwags["stderr"], type(subprocess.PIPE))
+
+
+@patch("psutil.cpu_count", lambda *args, **kwags: 5)
+@pytest.mark.parametrize("arg", [None, 3, 10])
+@pytest.mark.parametrize("env", [None, 3, 10])
+def test_get_cpus(monkeypatch, arg, env):
+    if env:
+        monkeypatch.setenv("PYMAPDL_NPROC", env)
+
+    context = NullContext()
+    cores_machine = psutil.cpu_count(logical=False)  # it is patched
+
+    if (arg and arg > cores_machine) or (arg is None and env and env > cores_machine):
+        context = pytest.raises(NotEnoughResources)
+
+    args = {"nproc": arg, "ON_SLURM": False}
+    with context:
+        get_cpus(args)
+
+    if arg:
+        assert args["nproc"] == arg
+    elif env:
+        assert args["nproc"] == env
+    else:
+        assert args["nproc"] == 2
+
+
+@patch("psutil.cpu_count", lambda *args, **kwags: 1)
+def test_get_cpus_min():
+    args = {"nproc": None, "ON_SLURM": False}
+    get_cpus(args)
+    assert args["nproc"] == 1