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[TESTING] Test correct setting and updating of particles.ei #3014

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[TESTING] Test correct setting and updating of particles.ei #3014

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8d3c90d
Adding test for checkoing pset.ei updating on xgrid
erikvansebille Oct 26, 2026
be7dc0e
Adding test for checking ei updating for ugrid
erikvansebille Oct 26, 2026
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9 changes: 2 additions & 7 deletions src/parcels/_core/particleset.py
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Original file line number Diff line number Diff line change
Expand Up @@ -264,13 +264,8 @@ def populate_indices(self):
"""Pre-populate guesses of particle ei (element id) indices"""
for i, grid in enumerate(self.fieldset.gridset):
grid_positions = grid.search(self.z, self.y, self.x)
self._data["ei"][:, i] = grid.ravel_index(
{
"X": grid_positions["X"]["index"],
"Y": grid_positions["Y"]["index"],
"Z": grid_positions["Z"]["index"],
}
)
axes = ("Z", "FACE") if isinstance(grid, UxGrid) else ("X", "Y", "Z")
self._data["ei"][:, i] = grid.ravel_index({axis: grid_positions[axis]["index"] for axis in axes})

@classmethod
def from_particlefile(cls, fieldset, pclass, filename, restart=True, restarttime=None, **kwargs):
Expand Down
39 changes: 39 additions & 0 deletions tests/test_advection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
Variable,
convert,
)
from parcels._core.field import _get_positions
from parcels._core.utils.time import timedelta_to_float
from parcels._core.warnings import FieldEvalWarning
from parcels._datasets.structured.generated import (
Expand All @@ -28,6 +29,7 @@
stommel_gyre_dataset,
)
from parcels._datasets.structured.generic import datasets_sgrid
from parcels._datasets.unstructured.generated import simple_small_delaunay
from parcels.kernels import (
RK2,
RK4,
Expand Down Expand Up @@ -153,6 +155,43 @@ def test_horizontal_advection_in_3D_flow(mesh_str, npart=10):
np.testing.assert_allclose(pset.x, expected_lon, atol=1.0e-1)


@pytest.mark.parametrize("npart", [1, 5])
def test_ei_update_during_xgrid_advection(npart):
ds = simple_UV_dataset(mesh_str="flat")
ds["U"].data[:] = 100.0
ds["V"].data[:] = -20.0
fieldset = FieldSet.from_sgrid_conventions(ds)

pset = ParticleSet(fieldset, x=np.linspace(0, 3e5, npart), y=np.zeros(npart))
pset.populate_indices()
ei_before = pset.ei.copy()

pset.execute(AdvectionRK4, runtime=np.timedelta64(1, "h"), dt=np.timedelta64(15, "m"))

_, grid_positions = _get_positions(fieldset.U, pset.t, pset.z, pset.y, pset.x, pset, pset.ei[:, 0])
ei_after = fieldset.U.grid.unravel_index(pset.ei[:, 0])
assert np.all(pset.ei != ei_before)
np.testing.assert_allclose(grid_positions["X"]["index"], ei_after["X"])
np.testing.assert_allclose(grid_positions["Y"]["index"], ei_after["Y"])


@pytest.mark.parametrize("npart", [1, 5])
def test_ei_update_during_ugrid_advection(npart):
ds = simple_small_delaunay()
fieldset = FieldSet.from_ugrid_conventions(ds)

pset = ParticleSet(fieldset, x=np.linspace(0.1, 0.8, npart), y=0.6 * np.ones(npart))
pset.populate_indices()
ei_before = pset.ei.copy()

pset.execute(AdvectionRK4, runtime=np.timedelta64(10, "h"), dt=np.timedelta64(15, "m"))

_, grid_positions = _get_positions(fieldset.U, pset.t, pset.z, pset.y, pset.x, pset, pset.ei[:, 0])
ei_after = fieldset.U.grid.unravel_index(pset.ei[:, 0])
assert np.all(pset.ei != ei_before)
np.testing.assert_allclose(grid_positions["FACE"]["index"], ei_after["FACE"])


@pytest.mark.parametrize("direction", ["up", "down"])
@pytest.mark.parametrize("resubmerge_particle", [True, False])
def test_advection_3D_outofbounds(direction, resubmerge_particle):
Expand Down
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