[feat] Add ability to specify number of nodes for slurm scheduler

docs/regression_test_api.rst

@@ -335,6 +335,7 @@ Mapping of Test Attributes to Job Scheduler Backends
    Test attribute               Slurm option                  Torque option                                                                              PBS option
    ============================ ============================= ========================================================================================== ==================
    :attr:`num_tasks`            :obj:`--ntasks`:sup:`1`       :obj:`-l nodes={num_tasks//num_tasks_per_node}:ppn={num_tasks_per_node*num_cpus_per_task}` :obj:`-l select={num_tasks//num_tasks_per_node}:mpiprocs={num_tasks_per_node}:ncpus={num_tasks_per_node*num_cpus_per_task}`
+   :attr:`num_nodes`            :obj:`--nodes`                n/a                                                                                        n/a
    :attr:`num_tasks_per_node`   :obj:`--ntasks-per-node`      see :attr:`num_tasks`                                                                      see :attr:`num_tasks`
    :attr:`num_tasks_per_core`   :obj:`--ntasks-per-core`      n/a                                                                                        n/a
    :attr:`num_tasks_per_socket` :obj:`--ntasks-per-socket`    n/a                                                                                        n/a

reframe/core/launchers/mpi.py

@@ -134,6 +134,9 @@ def command(self, job):
 
         if job.num_tasks:
             ret += ['--ntasks=%s' % str(job.num_tasks)]
+
+        if job.num_nodes:
+            ret += ['--nodes=%s' % str(job.num_nodes)]
 
         if job.num_tasks_per_node:
             ret += ['--ntasks-per-node=%s' % str(job.num_tasks_per_node)]

reframe/core/pipeline.py

@@ -527,8 +527,9 @@ def pipeline_hooks(cls):
     #: :attr:`num_tasks` to ``0`` is equivalent to setting it to
     #: :attr:`-num_tasks_per_node
     #: <reframe.core.pipeline.RegressionTest.num_tasks_per_node>`.
+    #: If set to :attr:`None` it will be omitted from any job scripts created and when combined with :attr:`num_nodes` this will allow a more flexible number of tasks to be run.
     #:
-    #: :type: integral
+    #: :type: integral or :class:`None`
     #: :default: ``1``
     #:
     #: .. note::
@@ -541,7 +542,16 @@ def pipeline_hooks(cls):
     #:
     #: .. |--flex-alloc-nodes| replace:: :attr:`--flex-alloc-nodes`
     #: .. _--flex-alloc-nodes: manpage.html#cmdoption-flex-alloc-nodes
-    num_tasks = variable(int, value=1, loggable=True)
+    num_tasks = variable(int,type(None), value=1, loggable=True)
+
+
+    #: Number of nodes for this job.
+    #:
+    #: :type: integral or :class:`None`
+    #: :default: ``None``
+    #:
+    #:
+    num_nodes = variable(int, type(None), value=None,loggable=True)
 
     #: Number of tasks per node required by this test.
     #:
@@ -1872,6 +1882,7 @@ def _get_cp_env():
                 )
 
         self.job.num_tasks = self.num_tasks
+        self.job.num_nodes = self.num_nodes
         self.job.num_tasks_per_node = self.num_tasks_per_node
         self.job.num_tasks_per_core = self.num_tasks_per_core
         self.job.num_tasks_per_socket = self.num_tasks_per_socket

reframe/core/schedulers/__init__.py

@@ -138,7 +138,17 @@ class Job(jsonext.JSONSerializable, metaclass=JobMeta):
     #:    based on the test information.
     #:
     #: .. versionadded:: 3.11.0
-    num_tasks = variable(int, value=1)
+    num_tasks = variable(int, type(None), value=1)
+
+
+
+    #: Number of nodes for this job.
+    #:
+    #: :type: integral or :class:`None`
+    #: :default: ``None``
+    #:
+    #:
+    num_nodes = variable(int, type(None), value=None)
 
     #: Number of tasks per node for this job.
     #:
@@ -461,7 +471,7 @@ def submit_time(self):
 
     def prepare(self, commands, environs=None, prepare_cmds=None, **gen_opts):
         environs = environs or []
-        if self.num_tasks <= 0:
+        if self.num_tasks!=None and self.num_tasks <= 0:
             getlogger().debug(f'[F] Flexible node allocation requested')
             num_tasks_per_node = self.num_tasks_per_node or 1
             min_num_tasks = (-self.num_tasks if self.num_tasks else

reframe/core/schedulers/slurm.py

@@ -169,6 +169,7 @@ def emit_preamble(self, job):
             self._format_option(job.num_tasks_per_socket,
                                 '--ntasks-per-socket={0}'),
             self._format_option(job.num_cpus_per_task, '--cpus-per-task={0}'),
+            self._format_option(job.num_nodes, '--nodes={0}')
         ]
 
         # Determine if job refers to a Slurm job array, by looking into the
@@ -199,7 +200,7 @@ def emit_preamble(self, job):
                 self._format_option(job.exclusive_access, '--exclusive')
             )
 
-        if self._use_nodes_opt:
+        if self._use_nodes_opt and job.num_nodes==None:
             num_nodes = job.num_tasks // job.num_tasks_per_node
             preamble.append(self._format_option(num_nodes, '--nodes={0}'))