added a test for dump and load (#224)

* added test_checkpoint and adapted poiseuille.py flow to new architecture

* pep8 cosmetics

tests/test_checkpoint.py

@@ -0,0 +1,53 @@
+from copy import deepcopy
+from tests.common import *
+
+
+def test_checkpoint(tmpdir):
+    context = Context()
+    flow = PoiseuilleFlow2D(context=context,
+                            resolution=[512, 512],
+                            reynolds_number=1,
+                            mach_number=0.02,
+                            initialize_with_zeros=False)
+    f0 = deepcopy(flow.f)
+    filename = tmpdir / 'PoiseuilleFlow2D'
+    flow.dump(filename)
+    simulation = Simulation(flow,
+                            BGKCollision(flow.units.relaxation_parameter_lu),
+                            [])
+    simulation(10)
+    flow.load(filename)
+    assert torch.eq(f0, flow.f).all()
+
+    """
+    This could be a way to test a dump-load workflow which stores all flow
+    attributes. I did not get it to work, yet.
+    context = Context('cuda')
+    flow = PoiseuilleFlow2D(context=context,
+                            resolution=16,
+                            reynolds_number=1,
+                            mach_number=0.02,
+                            initialize_with_zeros=False)
+    f0 = deepcopy(flow.f)
+    filename = './PoiseuilleFlow2D'
+    flow.dump(filename)
+
+    simulation = Simulation(flow,
+                            BGKCollision(flow.units.relaxation_parameter_lu),
+                            [])
+    simulation(10)
+
+    context2 = Context('cpu')
+    flow2 = PoiseuilleFlow2D(context=context2,
+                             resolution=32,
+                             reynolds_number=10,
+                             mach_number=0.01,
+                             initialize_with_zeros=True)
+    flow2.load(filename)
+
+    assert flow2.resolution == flow.resolution
+    assert flow2.units.reynolds_number == flow.units.reynolds_number
+    assert flow2.units.mach_number == flow.units.mach_number
+    assert flow2.initialize_with_zeros == flow.initialize_with_zeros
+    assert torch.eq(f0, flow2.f).all()
+    """