Supports building mapping files with multiple MPI tasks

For now, this only works on systems with mpirun (not srun, etc.)

pyremap/remapper.py

@@ -97,8 +97,8 @@ def __init__(self, sourceDescriptor, destinationDescriptor,
 
         # }}}
 
-    def build_mapping_file(self, method='bilinear',
-                           additionalArgs=None, logger=None):  # {{{
+    def build_mapping_file(self, method='bilinear', additionalArgs=None,
+                           logger=None, mpiTasks=1):  # {{{
         '''
         Given a source file defining either an MPAS mesh or a lat-lon grid and
         a destination file or set of arrays defining a lat-lon grid, constructs
@@ -117,6 +117,10 @@ def build_mapping_file(self, method='bilinear',
         logger : ``logging.Logger``, optional
             A logger to which ncclimo output should be redirected
 
+        mpiTasks : int, optional
+            The number of MPI tasks (a number > 1 implies that
+            ESMF_RegridWeightGen will be called with ``mpirun``)
+
         Raises
         ------
         OSError
@@ -141,7 +145,9 @@ def build_mapping_file(self, method='bilinear',
             # a valid weight file already exists, so nothing to do
             return
 
-        if find_executable('ESMF_RegridWeightGen') is None:
+        rwgPath = find_executable('ESMF_RegridWeightGen')
+
+        if rwgPath is None:
             raise OSError('ESMF_RegridWeightGen not found. Make sure esmf '
                           'package is installed via\n'
                           'latest nco: \n'
@@ -153,14 +159,17 @@ def build_mapping_file(self, method='bilinear',
         self.sourceDescriptor.to_scrip(_get_temp_path())
         self.destinationDescriptor.to_scrip(_get_temp_path())
 
-        args = ['ESMF_RegridWeightGen',
+        args = [rwgPath,
                 '--source', self.sourceDescriptor.scripFileName,
                 '--destination', self.destinationDescriptor.scripFileName,
                 '--weight', self.mappingFileName,
                 '--method', method,
                 '--netcdf4',
                 '--no_log']
 
+        if mpiTasks > 1:
+            args = ['mpirun', '-np', '{}'.format(mpiTasks)] + args
+
         if self.sourceDescriptor.regional:
             args.append('--src_regional')