grass.pygrass: GridModule: fix no-data rows at tile borders (#2736)

Fixes #2678 by avoiding unnecessary nsew <-> row,col conversions

python/grass/pygrass/modules/grid/grid.py

@@ -23,7 +23,10 @@
 from grass.pygrass.modules import Module
 from grass.pygrass.utils import get_mapset_raster, findmaps
 
-from grass.pygrass.modules.grid.split import split_region_tiles
+from grass.pygrass.modules.grid.split import (
+    split_region_tiles,
+    split_region_in_overlapping_tiles,
+)
 from grass.pygrass.modules.grid.patch import rpatch_map, rpatch_map_r_patch_backend
 
 
@@ -515,7 +518,7 @@ def __init__(
             groups = [g for g in select(self.module.inputs, "group")]
             if groups:
                 copy_groups(groups, self.gisrc_src, self.gisrc_dst, region=self.region)
-        self.bboxes = split_region_tiles(
+        self.bboxes = split_region_in_overlapping_tiles(
             region=region, width=self.width, height=self.height, overlap=overlap
         )
         if mapset_prefix:

python/grass/pygrass/modules/grid/patch.py

@@ -18,23 +18,6 @@
 from grass.pygrass.modules import Module
 
 
-def get_start_end_index(bbox_list):
-    """Convert a Bounding Box to a list of the index of
-    column start, end, row start and end
-
-    :param bbox_list: a list of BBox object to convert
-    :type bbox_list: list of BBox object
-
-    """
-    ss_list = []
-    reg = Region()
-    for bbox in bbox_list:
-        r_start, c_start = coor2pixel((bbox.west, bbox.north), reg)
-        r_end, c_end = coor2pixel((bbox.east, bbox.south), reg)
-        ss_list.append((int(r_start), int(r_end), int(c_start), int(c_end)))
-    return ss_list
-
-
 def rpatch_row(rast, rasts, bboxes):
     """Patch a row of bound boxes.
 
@@ -45,16 +28,15 @@ def rpatch_row(rast, rasts, bboxes):
     :param bboxes: a list of BBox object
     :type bboxes: list of BBox object
     """
-    sei = get_start_end_index(bboxes)
     # instantiate two buffer
     buff = rasts[0][0]
     rbuff = rasts[0][0]
-    r_start, r_end, c_start, c_end = sei[0]
-    for row in range(r_start, r_end):
+    r_start, r_end, c_start, c_end = bboxes[0]
+    for row in range(r_start, r_end + 1):
         for col, ras in enumerate(rasts):
-            r_start, r_end, c_start, c_end = sei[col]
+            r_start, r_end, c_start, c_end = bboxes[col]
             buff = ras.get_row(row, buff)
-            rbuff[c_start:c_end] = buff[c_start:c_end]
+            rbuff[c_start : c_end + 1] = buff[c_start : c_end + 1]
         rast.put_row(rbuff)
 
 

python/grass/pygrass/modules/grid/split.py

@@ -44,8 +44,31 @@ def get_bbox(reg, row, col, width, height, overlap):
     )
 
 
-def split_region_tiles(region=None, width=100, height=100, overlap=0):
-    """Spit a region into a list of Bbox.
+def get_tile_start_end_row_col(reg, row, col, width, height):
+    """Return a tile's starting and ending row and col
+
+    :param reg: a Region object to split
+    :type reg: Region object
+    :param row: the number of tiles in a row
+    :type row: int
+    :param col: the number of tiles in a col
+    :type col: int
+    :param width: the width of tiles
+    :type width: int
+    :param height: the width of tiles
+    :type height: int
+    """
+    start_row = row * height
+    end_row = (row + 1) * height - 1
+    start_col = col * width
+    end_col = (col + 1) * width - 1
+    end_row = reg.rows - 1 if end_row >= reg.rows else end_row
+    end_col = reg.cols - 1 if end_col >= reg.cols else end_col
+    return (start_row, end_row, start_col, end_col)
+
+
+def split_region_in_overlapping_tiles(region=None, width=100, height=100, overlap=0):
+    """Split a region into a list of overlapping tiles defined as (N, S, E, W).
 
     :param region: a Region object to split
     :type region: Region object
@@ -67,10 +90,10 @@ def split_region_tiles(region=None, width=100, height=100, overlap=0):
     1500
     >>> reg.rows
     1350
-    >>> split_region_tiles(region=reg, width=1000, height=700, overlap=0) # doctest: +NORMALIZE_WHITESPACE
+    >>> split_region_in_overlapping_tiles(region=reg, width=1000, height=700, overlap=0) # doctest: +NORMALIZE_WHITESPACE
     [[Bbox(1350.0, 650.0, 1000.0, 0.0), Bbox(1350.0, 650.0, 1500.0, 1000.0)],
      [Bbox(650.0, 0.0, 1000.0, 0.0), Bbox(650.0, 0.0, 1500.0, 1000.0)]]
-    >>> split_region_tiles(region=reg, width=1000, height=700, overlap=10) # doctest: +NORMALIZE_WHITESPACE
+    >>> split_region_in_overlapping_tiles(region=reg, width=1000, height=700, overlap=10) # doctest: +NORMALIZE_WHITESPACE
     [[Bbox(1350.0, 640.0, 1010.0, 0.0), Bbox(1350.0, 640.0, 1500.0, 990.0)],
      [Bbox(660.0, 0.0, 1010.0, 0.0), Bbox(660.0, 0.0, 1500.0, 990.0)]]
     """
@@ -88,6 +111,28 @@ def split_region_tiles(region=None, width=100, height=100, overlap=0):
     return box_list
 
 
+def split_region_tiles(region=None, width=100, height=100):
+    """Split a region into a list of tiles defined as (start_row, end_row, start_col, end_col).
+
+    :param region: a Region object to split
+    :type region: Region object
+    :param width: the width of tiles
+    :type width: int
+    :param height: the width of tiles
+    :type height: int
+    """
+    reg = region if region else Region()
+    ncols = (reg.cols + width - 1) // width
+    nrows = (reg.rows + height - 1) // height
+    box_list = []
+    for row in range(nrows):
+        row_list = []
+        for col in range(ncols):
+            row_list.append(get_tile_start_end_row_col(reg, row, col, width, height))
+        box_list.append(row_list)
+    return box_list
+
+
 def get_overlap_region_tiles(region=None, width=100, height=100, overlap=0):
     """Get the Bbox of the overlapped region.
 

python/grass/pygrass/modules/tests/grass_pygrass_grid_test.py

@@ -253,3 +253,42 @@ def run_grid_module():
 
         info = gs.raster_info("slope")
         assert info["min"] > 0
+
+
+@pytest.mark.parametrize(
+    "processes, backend",
+    [
+        (1, "RasterRow"),
+        (9, "RasterRow"),
+        (9, "r.patch"),
+        (10, "RasterRow"),
+        (10, "r.patch"),
+    ],
+)
+def test_patching_error(tmp_path, processes, backend):
+    """Check auto adjusted tile size based on processes"""
+    location = "test"
+    gs.core._create_location_xy(tmp_path, location)  # pylint: disable=protected-access
+    with gs.setup.init(tmp_path / location):
+        gs.run_command("g.region", s=0, n=10, w=0, e=10, res=0.1)
+        surface = "fractal"
+
+        def run_grid_module():
+            # modules/shortcuts calls get_commands which requires GISBASE.
+            # pylint: disable=import-outside-toplevel
+            from grass.pygrass.modules.grid import GridModule
+
+            grid = GridModule(
+                "r.surf.fractal",
+                overlap=0,
+                processes=processes,
+                output=surface,
+                patch_backend=backend,
+                debug=True,
+            )
+            grid.run()
+
+        run_in_subprocess(run_grid_module)
+
+        info = gs.parse_command("r.univar", flags="g", map=surface)
+        assert int(info["null_cells"]) == 0