Make fillsinks memory-order agnostic (TopoToolbox#125)

This change represents one way that we might make our interface with libtopotoolbox agnostic to the memory order of our underlying numpy arrays. I have added a property dims to GridObject, which reverses the order of the dimensions if the array is in row-major layout. GridObject.shape still returns (rows, columns). If we pass self.dims instead of self.shape to the fillsinks wrapper, we will now get the same, correct, answer if the GridObject.z array is column- or row-major. There is also a test that confirms this behavior.

src/topotoolbox/grid_object.py

@@ -64,6 +64,18 @@ def columns(self):
         """
         return self.z.shape[1]
 
+    @property
+    def dims(self):
+        """The dimensions of the grid in the correct order for libtopotoolbox
+        """
+        if self.z.flags.c_contiguous:
+            return (self.columns, self.rows)
+
+        if self.z.flags.f_contiguous:
+            return (self.rows, self.columns)
+
+        raise TypeError("Grid is not stored as a contiguous row- or column-major array")
+
     def reproject(self,
                   crs: 'CRS',
                   resolution: 'float | None' = None,
@@ -137,7 +149,7 @@ def fillsinks(self,
 
         """
 
-        dem = self.z.astype(np.float32, order='F')
+        dem = self.z.astype(np.float32)
         output = np.zeros_like(dem)
 
         restore_nans = False
@@ -161,9 +173,9 @@ def fillsinks(self,
 
         if hybrid:
             queue = np.zeros_like(dem, dtype=np.int64)
-            _grid.fillsinks_hybrid(output, queue, dem, bc, self.shape)
+            _grid.fillsinks_hybrid(output, queue, dem, bc, self.dims)
         else:
-            _grid.fillsinks(output, dem, bc, self.shape)
+            _grid.fillsinks(output, dem, bc, self.dims)
 
         if restore_nans:
             dem[nans] = np.nan

tests/test_grid_object.py

@@ -3,6 +3,8 @@
 
 import topotoolbox as topo
 
+import opensimplex
+
 
 @pytest.fixture
 def square_dem():
@@ -67,6 +69,40 @@ def test_fillsinks(square_dem, wide_dem, tall_dem):
                 assert sink < 8
 
 
+def test_fillsinks_order():
+    opensimplex.seed(12)
+
+    x = np.arange(0,128)
+    y = np.arange(0,256)
+
+    dem_C = topo.GridObject()
+    dem_C.z = 64 * (opensimplex.noise2array(x,y) + 1)
+
+    assert dem_C.shape[0] == 256
+    assert dem_C.shape[1] == 128
+
+    assert dem_C.z.flags.c_contiguous
+    assert dem_C.dims[0] == 128
+    assert dem_C.dims[1] == 256
+
+    dem_F = topo.GridObject()
+    dem_F.z = np.asfortranarray(dem_C.z)
+
+    assert dem_F.shape[0] == 256
+    assert dem_F.shape[1] == 128
+
+    assert dem_F.z.flags.f_contiguous
+    assert dem_F.dims[0] == 256
+    assert dem_F.dims[1] == 128
+
+    filled_C = dem_C.fillsinks()
+    assert filled_C.z.flags.c_contiguous
+
+    filled_F = dem_F.fillsinks()    
+    assert filled_F.z.flags.f_contiguous
+
+    assert np.array_equal(filled_F.z, filled_C.z)
+
 def test_identifyflats(square_dem, wide_dem, tall_dem):
     # TODO: add more tests
     for dem in [square_dem, wide_dem, tall_dem]: