compiler: Privilege default par-tile with rcompile

Author: FabioLuporini

devito/core/gpu.py

@@ -126,16 +126,25 @@ def _rcompile_wrapper(cls, **kwargs0):
 
         def wrapper(expressions, mode='default', options=None, **kwargs1):
             kwargs = {**kwargs0, **kwargs1}
+            options = options or {}
 
             if mode == 'host':
-                options = options or {}
                 target = {
                     'platform': 'cpu64',
                     'language': 'C' if options0['par-disabled'] else 'openmp',
                     'compiler': 'custom'
                 }
             else:
-                options = {**options0, **(options or {})}
+                # Always use the default `par-tile` for recursive compilation
+                # unless the caller explicitly overrides it so that if the user
+                # supplies a multi par-tile there is no need to worry about the
+                # small kernels typically generated by recursive compilation
+                par_tile = options.get('par-tile')
+                if not par_tile:
+                    par_tile = options0['par-tile']
+                    par_tile = ParTile(par_tile.default, default=par_tile.default)
+                options = {**options0, **options, 'par-tile': par_tile}
+
                 target = None
 
             return rcompile(expressions, kwargs, options, target=target)