Setting particleset.time to NaT on init when not provided

Since we don't know on particleset initialisation whether the execute will be forward or backward in time, we can't yet decide whether the time should be time_interval.left or time_interval.right. Hence, setting to "NaT" until we know the sign of dt

Author: erikvansebille

parcels/particleset.py

@@ -110,7 +110,7 @@ def __init__(
         assert lon.size == lat.size and lon.size == depth.size, "lon, lat, depth don't all have the same lenghts"
 
         if time is None or len(time) == 0:
-            time = fieldset.U.time.values[0]  # TODO set this to NaT if no time is given
+            time = np.datetime64("NaT", "ns")  # do not set a time yet (because sign_dt not known)
         elif type(time[0]) in [np.datetime64, np.timedelta64]:
             pass  # already in the right format
         else:
@@ -753,7 +753,16 @@ def execute(
                     raise TypeError("The runtime must be a np.timedelta64 object")
 
         else:
-            start_time = self._data["time_nextloop"].min().values
+            if not np.isnat(self._data["time_nextloop"]).any():
+                if sign_dt > 0:
+                    start_time = self._data["time_nextloop"].min().values
+                else:
+                    start_time = self._data["time_nextloop"].max().values
+            else:
+                if sign_dt > 0:
+                    start_time = self.fieldset.time_interval.left
+                else:
+                    start_time = self.fieldset.time_interval.right
 
             if runtime is None:
                 if endtime is None:
@@ -777,6 +786,11 @@ def execute(
             else:
                 end_time = start_time + runtime * sign_dt
 
+        # Set the time of the particles if it hadn't been set on initialisation
+        if np.isnat(self._data["time"]).any():
+            self._data["time"][:] = start_time
+            self._data["time_nextloop"][:] = start_time
+
         outputdt = output_file.outputdt if output_file else None
 
         # Set up pbar

tests/v4/test_particleset.py

@@ -138,7 +138,7 @@ def test_particleset_dt_type(fieldset, dt, expectation):
 
 def test_pset_starttime_not_multiple_dt(fieldset):
     times = [0, 1, 2]
-    datetimes = [fieldset.U.time[0].values + np.timedelta64(t, "s") for t in times]
+    datetimes = [fieldset.time_interval.left + np.timedelta64(t, "s") for t in times]
     pset = ParticleSet(fieldset, lon=[0] * len(times), lat=[0] * len(times), pclass=Particle, time=datetimes)
 
     def Addlon(particle, fieldset, time):  # pragma: no cover

tests/v4/test_particleset_execute.py

@@ -43,11 +43,11 @@ def test_pset_stop_simulation(fieldset):
     pset = ParticleSet(fieldset, lon=0, lat=0, pclass=Particle)
 
     def Delete(particle, fieldset, time):  # pragma: no cover
-        if time >= fieldset.U.time[0].values + np.timedelta64(4, "s"):
+        if time >= fieldset.time_interval.left + np.timedelta64(4, "s"):
             return StatusCode.StopExecution
 
     pset.execute(Delete, dt=np.timedelta64(1, "s"), runtime=np.timedelta64(21, "s"))
-    assert pset[0].time == fieldset.U.time[0].values + np.timedelta64(4, "s")
+    assert pset[0].time == fieldset.time_interval.left + np.timedelta64(4, "s")
 
 
 @pytest.mark.parametrize("with_delete", [True, False])