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Fixing error for RK45 on spherical grids #2827

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Merged
erikvansebille merged 2 commits into from
Aug 17, 2026
Merged

Fixing error for RK45 on spherical grids #2827

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7c3baa0
Fixing error for RK45 on spherical grids
erikvansebille Aug 14, 2026
730591b
Merge branch 'main' into fix_rk45_tol
erikvansebille Aug 17, 2026
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4 changes: 1 addition & 3 deletions src/parcels/_core/kernel.py
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Original file line number Diff line number Diff line change
Expand Up @@ -142,9 +142,7 @@ def check_fieldsets_in_kernels(self, kernel): # TODO v4: this can go into anoth
)
self.fieldset.add_context("RK45_tol", 10)
if self.fieldset.U.grid._mesh.is_spherical():
self.fieldset.RK45_tol /= (
self.fieldset.U.grid.deg2m
) # TODO does not account for zonal variation in meter -> degree conversion

@erikvansebille erikvansebille Aug 14, 2026

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I don't think this TODO is relevant anymore - we didn't do this in v3 either and it would require a major refactoring

self.fieldset.context["RK45_tol"] = self.fieldset.RK45_tol / self.fieldset.U.grid.deg2m
if not hasattr(self.fieldset, "RK45_min_dt"):
warnings.warn(
"Setting RK45 minimum timestep to 1 s. Use fieldset.add_context('RK45_min_dt', [timestep]) to change.",
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7 changes: 4 additions & 3 deletions tests/test_advection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -395,11 +395,12 @@ def UpdateP(particles, fieldset): # pragma: no cover
(AdvectionRK45, 1e-3),
],
)
@pytest.mark.parametrize("mesh", ["flat", "spherical"])
@pytest.mark.parametrize("grid_type", ["A", "C"])
def test_peninsula_fieldset(kernel, rtol, grid_type):
def test_peninsula_fieldset(kernel, rtol, grid_type, mesh):
npart = 2
ds = peninsula_dataset(grid_type=grid_type)
fieldset = FieldSet.from_sgrid_conventions(ds, mesh="flat")
fieldset = FieldSet.from_sgrid_conventions(ds, mesh=mesh)

dt = np.timedelta64(30, "m")
runtime = np.timedelta64(23, "h")
Expand All @@ -412,7 +413,7 @@ def test_peninsula_fieldset(kernel, rtol, grid_type):

if kernel == AdvectionRK45:
fieldset.add_context("RK45_tol", rtol)
fieldset.add_context("RK45_min_dt", 1)
fieldset.add_context("RK45_min_dt", 10)

@erikvansebille erikvansebille Aug 14, 2026

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For a (slight) speedup of the tests

fieldset.add_context("RK45_max_dt", 24 * 60 * 60)

def UpdateP(particles, fieldset): # pragma: no cover
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