Throwing an error when dt has too high precision

Author: erikvansebille

docs/examples/example_globcurrent.py

@@ -260,3 +260,22 @@ def test_globcurrent_pset_fromfile(mode, dt, pid_offset, tmpdir):
 
     for var in ['lon', 'lat', 'depth', 'time', 'id']:
         assert np.allclose([getattr(p, var) for p in pset], [getattr(p, var) for p in pset_new])
+
+
+@pytest.mark.parametrize('mode', ['scipy', 'jit'])
+def test_error_outputdt_not_multiple_dt(mode, tmpdir):
+    # Test that outputdt is a multiple of dt
+    fieldset = set_globcurrent_fieldset()
+
+    filepath = tmpdir.join("pfile_error_outputdt_not_multiple_dt.zarr")
+
+    dt = 81.2584344538292  # number for which output writing fails
+
+    pset = ParticleSet(fieldset, pclass=ptype[mode], lon=[0], lat=[0])
+    ofile = pset.ParticleFile(name=filepath, outputdt=delta(days=1))
+
+    def DoNothing(particle, fieldset, time):
+        pass
+
+    with pytest.raises(ValueError):
+        pset.execute(DoNothing, runtime=delta(days=10), dt=dt, output_file=ofile)

parcels/particleset.py

@@ -878,8 +878,10 @@ def execute(self, pyfunc=AdvectionRK4, pyfunc_inter=None, endtime=None, runtime=
             runtime = runtime.total_seconds()
         if isinstance(dt, delta):
             dt = dt.total_seconds()
-        if dt > 0 and dt <= 1e-6:
+        if abs(dt) <= 1e-6:
             raise ValueError('Time step dt is too small')
+        if dt*1e6 % 1 != 0:
+            raise ValueError('Output interval should not have finer precision than 1e-6 s')
         outputdt = output_file.outputdt if output_file else np.infty
         if isinstance(outputdt, delta):
             outputdt = outputdt.total_seconds()