Automatically get cores_per_node on single node

compass/machines/default.cfg

@@ -1,4 +1,3 @@
-
 # The parallel section describes options related to running tests in parallel
 [parallel]
 
@@ -7,6 +6,3 @@ system = single_node
 
 # whether to use mpirun or srun to run the model
 parallel_executable = mpirun
-
-# cores per node on the machine
-cores_per_node = 4

compass/parallel.py

@@ -30,8 +30,10 @@ def get_available_cores_and_nodes(config):
         args = ['squeue', '--noheader', '-j', job_id, '-o', '%D']
         nodes = _get_subprocess_int(args)
     elif parallel_system == 'single_node':
-        cores_per_node = config.getint('parallel', 'cores_per_node')
-        cores = min(multiprocessing.cpu_count(), cores_per_node)
+        cores = multiprocessing.cpu_count()
+        if config.has_option('parallel', 'cores_per_node'):
+            cores_per_node = config.getint('parallel', 'cores_per_node')
+            cores = min(cores, cores_per_node)
         nodes = 1
     else:
         raise ValueError('Unexpected parallel system: {}'.format(
@@ -90,6 +92,10 @@ def set_cores_per_node(config):
         if old_cpus_per_node != cpus_per_node:
             warnings.warn(f'Slurm found {cpus_per_node} cpus per node but '
                           f'config from mache was {old_cpus_per_node}')
+    elif parallel_system == 'single_node':
+        if not config.has_option('parallel', 'cores_per_node'):
+            cores = multiprocessing.cpu_count()
+            config.set('parallel', 'cores_per_node', f'{cores}')
 
 
 def _get_subprocess_int(args):

docs/users_guide/machines/index.rst

@@ -171,13 +171,10 @@ in your user config file:
     system = single_node
 
     # whether to use mpirun or srun to run the model
-    parallel_executable = mpirun
+    parallel_executable = mpirun -host localhost
 
-    # cores per node on the machine
-    cores_per_node = 4
-
-    # the number of multiprocessing or dask threads to use
-    threads = 4
+    # cores per node on the machine, detected automatically by default
+    # cores_per_node = 4
 
 The paths for the MPAS core "databases" can be any emtpy path to begin with.
 If the path doesn't exist, ``compass`` will create it.

docs/users_guide/quick_start.rst

@@ -301,20 +301,17 @@ in the repository.
     # whether to use mpirun or srun to run the model
     parallel_executable = mpirun -host localhost
 
-    # cores per node on the machine
-    cores_per_node = 4
-
-    # the number of multiprocessing or dask threads to use
-    threads = 4
+    # cores per node on the machine, detected automatically by default
+    # cores_per_node = 4
 
 The two ``*_database_root`` directories can point to locations where you would
 like to download data for MALI and MPAS-Ocean.  This data is downloaded only
 once and cached for the next time you call ``compass setup`` or
 ``compass suite`` (see below).
 
-The ``cores_per_node`` and ``threads`` config options should be the number of
-CPUs on your computer.  You can set this to a smaller number if you want
-``compass``.
+The ``cores_per_node`` config option will default to the number of CPUs on your
+computer.  You can set this to a smaller number if you want ``compass`` to
+use fewer cores.
 
 In order to run regression testing that compares the output of the current run
 with that from a previous compass run, use ``-b <previous_workdir>`` to specify

example_configs/landice.cfg

@@ -22,11 +22,8 @@ system = single_node
 # whether to use mpirun or srun to run the model
 parallel_executable = mpirun -host localhost
 
-# cores per node on the machine
-cores_per_node = 4
-
-# the number of multiprocessing or dask threads to use
-threads = 4
+# cores per node on the machine, detected automatically by default
+# cores_per_node = 4
 
 
 # Options related to downloading files

example_configs/ocean.cfg

@@ -23,11 +23,8 @@ system = single_node
 # whether to use mpirun or srun to run the model
 parallel_executable = mpirun -host localhost
 
-# cores per node on the machine
-cores_per_node = 4
-
-# the number of multiprocessing or dask threads to use
-threads = 4
+# cores per node on the machine, detected automatically by default
+# cores_per_node = 4
 
 
 # Options related to downloading files