Add structured grid spherical spatialhash query tests

Tests for both points inside the domain and explicitly outside the domain
to confirm correct behavior for out of bounds PIC checks

Author: fluidnumericsJoe

tests/test_spatialhash.py

@@ -20,6 +20,40 @@ def test_invalid_positions():
     assert np.all(i == -3)
 
 
+def test_spherical_regional_bounds():
+    """Hash-grid bounds for spherical meshes are the Cartesian bounding box of the
+    (regional) grid, not the whole unit cube, so quantization resolution is not
+    wasted on parts of the sphere the grid does not cover.
+    """
+    ds = datasets["2d_left_rotated"]
+    grid = FieldSet.from_sgrid_conventions(ds, mesh="spherical").data_g.grid
+    spatialhash = grid.get_spatial_hash()
+
+    extents = np.array(
+        [
+            spatialhash._xmax - spatialhash._xmin,
+            spatialhash._ymax - spatialhash._ymin,
+            spatialhash._zmax - spatialhash._zmin,
+        ]
+    )
+    assert np.all(extents > 0.0)
+    assert np.all(extents < 2.0)  # strictly tighter than the unit cube
+
+    # Queries at cell centers must still resolve to the correct cell
+    lon, lat = grid.lon, grid.lat
+    clon = 0.25 * (lon[:-1, :-1] + lon[:-1, 1:] + lon[1:, :-1] + lon[1:, 1:])
+    clat = 0.25 * (lat[:-1, :-1] + lat[:-1, 1:] + lat[1:, :-1] + lat[1:, 1:])
+    jj, ii = np.meshgrid(np.arange(clat.shape[0]), np.arange(clat.shape[1]), indexing="ij")
+    j, i, _ = spatialhash.query(clat.ravel(), clon.ravel())
+    assert np.array_equal(j, jj.ravel())
+    assert np.array_equal(i, ii.ravel())
+
+    # Points far outside the regional domain must not match any cell
+    j, i, _ = spatialhash.query([-60.0, 80.0], [120.0, -150.0])
+    assert np.all(j == -3)
+    assert np.all(i == -3)
+
+
 def test_mixed_positions():
     ds = datasets["2d_left_rotated"]
     grid = FieldSet.from_sgrid_conventions(ds, mesh="flat").data_g.grid