WIP: Graph datahandling

This is the draft for a data handling that (optionally) forwards all calls to SerialDatahandling. All calls and data transfers get recorded for the creation of an execution graph.

Needs to be changed after the breaking changes in datahandling.

Needs a tiny change in lbmpy:

Instead of using TimeLoop(...) for time loop creation a custom function is used.

pystencils/datahandling/graph_datahandling.py

@@ -7,13 +7,13 @@
 """
 
 """
-
 from enum import Enum
 
 import numpy as np
 
 import pystencils.datahandling
 import pystencils.kernel_wrapper
+import pystencils.timeloop
 from pystencils.field import FieldType
 
 
@@ -181,7 +181,7 @@ class GraphDataHandling(pystencils.datahandling.SerialDataHandling):
 
     def synchronization_function(self, names, stencil=None, target=None, **_):
         for name in names:
-            gpu = target == 'cpu'
+            gpu = target == 'gpu'
             self.call_queue.append(Communication(self._fields[name], stencil, gpu))
         super().synchronization_function(names, stencil=None, target=None, **_)