add continue feature for depletion

openmc/deplete/abc.py

@@ -515,6 +515,18 @@ class Integrator(ABC):
         :attr:`solver`.
 
         .. versionadded:: 0.12
+    continue_timesteps : bool, optional
+        Whether or not to treat the current solve as a continuation of a
+        previous simulation. Defaults to `False`. If `True`, the timesteps
+        provided to the `Integrator` must match exactly those that exist
+        in the `prev_results` passed to the `Operator`. The `power`,
+        `power_density`, or `source_rates` must match as well. It
+        is the user's responsibility to make sure that the continue
+        solve uses the same method of specifying `power`, `power_density`,
+        or `source_rates`.
+
+        .. versionadded:: 0.15.1
+
     Attributes
     ----------
     operator : openmc.deplete.abc.TransportOperator
@@ -556,7 +568,8 @@ def __init__(
             power_density: Optional[Union[float, Sequence[float]]] = None,
             source_rates: Optional[Sequence[float]] = None,
             timestep_units: str = 's',
-            solver: str = "cram48"
+            solver: str = "cram48",
+            continue_timesteps: bool = False,
         ):
         # Check number of stages previously used
         if operator.prev_res is not None:
@@ -629,6 +642,24 @@ def __init__(
             else:
                 raise ValueError(f"Invalid timestep unit '{unit}'")
 
+            # validate existing depletion steps are consistent with those passed to operator
+            if continue_timesteps:
+                completed_timesteps = operator.prev_res.get_times()
+                completed_source_rates = operator.prev_res.get_source_rates()
+                num_previous_steps_run = len(completed_timesteps)
+                if (
+                    np.array_equal(completed_timesteps, timesteps[:num_previous_steps_run]) and
+                    np.array_equal(completed_source_rates, source_rates[:num_previous_steps_run])
+                ):
+                    seconds = seconds[num_previous_steps_run:]
+                    source_rates = source_rates[num_previous_steps_run:]
+                else:
+                    raise ValueError(
+                        "You are attempting to continue a run in which the previous results "
+                        "do not have the same initial steps as those provided to the "
+                        "Integrator. Please make sure you are using the correct timesteps, "
+                        "powers or power densities, and previous results file."
+                    )
         self.timesteps = np.asarray(seconds)
         self.source_rates = np.asarray(source_rates)
 
@@ -919,6 +950,17 @@ class SIIntegrator(Integrator):
         :attr:`solver`.
 
         .. versionadded:: 0.12
+    continue_timesteps : bool, optional
+        Whether or not to treat the current solve as a continuation of a
+        previous simulation. Defaults to `False`. If `True`, the timesteps
+        provided to the `Integrator` must match exactly those that exist
+        in the `prev_results` passed to the `Opereator`. The `power`,
+        `power_density`, or `source_rates` must match as well. It
+        is the user's responsibility to make sure that the continue
+        solve uses the same method of specifying `power`, `power_density`,
+        or `source_rates`.
+
+        .. versionadded:: 0.15.1
 
     Attributes
     ----------
@@ -960,13 +1002,14 @@ def __init__(
             source_rates: Optional[Sequence[float]] = None,
             timestep_units: str = 's',
             n_steps: int = 10,
-            solver: str = "cram48"
+            solver: str = "cram48",
+            continue_timesteps: bool = False,
         ):
         check_type("n_steps", n_steps, Integral)
         check_greater_than("n_steps", n_steps, 0)
         super().__init__(
             operator, timesteps, power, power_density, source_rates,
-            timestep_units=timestep_units, solver=solver)
+            timestep_units=timestep_units, solver=solver, continue_timesteps=continue_timesteps)
         self.n_steps = n_steps
 
     def _get_bos_data_from_operator(self, step_index, step_power, n_bos):

openmc/deplete/results.py

@@ -17,6 +17,10 @@
 
 __all__ = ["Results", "ResultsList"]
 
+_SECONDS_PER_MINUTE = 60
+_SECONDS_PER_HOUR = 60*60
+_SECONDS_PER_DAY = 24*60*60
+_SECONDS_PER_JULIAN_YEAR = 365.25*24*60*60
 
 def _get_time_as(seconds: float, units: str) -> float:
     """Converts the time in seconds to time in different units
@@ -31,13 +35,13 @@ def _get_time_as(seconds: float, units: str) -> float:
 
     """
     if units == "a":
-        return seconds / (60 * 60 * 24 * 365.25)  # 365.25 due to the leap year
+        return seconds / _SECONDS_PER_JULIAN_YEAR
     if units == "d":
-        return seconds / (60 * 60 * 24)
+        return seconds / _SECONDS_PER_DAY
     elif units == "h":
-        return seconds / (60 * 60)
+        return seconds / _SECONDS_PER_HOUR
     elif units == "min":
-        return seconds / 60
+        return seconds / _SECONDS_PER_MINUTE
     else:
         return seconds
 
@@ -71,7 +75,6 @@ def __init__(self, filename='depletion_results.h5'):
                     data.append(StepResult.from_hdf5(fh, i))
         super().__init__(data)
 
-
     @classmethod
     def from_hdf5(cls, filename: PathLike):
         """Load in depletion results from a previous file
@@ -460,6 +463,25 @@ def get_times(self, time_units: str = "d") -> np.ndarray:
 
         return _get_time_as(times, time_units)
 
+    def get_source_rates(self) -> np.ndarray:
+        """
+        .. versionadded:: 0.15.1
+
+        Returns
+        -------
+        numpy.ndarray
+            1-D vector of source rates at each point in the depletion simulation
+            with the units originally defined by the user.
+
+        """
+        source_rates = np.fromiter(
+            (r.source_rate for r in self),
+            dtype=self[0].source_rate.dtype,
+            count=len(self)-1,
+        ) # Results duplicates the final source rate at the final simulation time
+
+        return source_rates
+
     def get_step_where(
         self, time, time_units: str = "d", atol: float = 1e-6, rtol: float = 1e-3
     ) -> int:

tests/unit_tests/test_deplete_continue.py

@@ -0,0 +1,90 @@
+"""Unit tests for openmc.deplete continue run capability.
+
+These tests run in two steps: first a normal run and then a continue run based on the prev_results
+"""
+
+import pytest
+
+import openmc.deplete
+
+from tests import dummy_operator
+
+# test that the continue timesteps works when the second integrate call contains all previous timesteps
+@pytest.mark.parametrize("scheme", dummy_operator.SCHEMES)
+def test_continue(run_in_tmpdir, scheme):
+    """Test to ensure that a properly defined continue run works"""
+
+    # set up the problem
+
+    bundle = dummy_operator.SCHEMES[scheme]
+
+    operator = dummy_operator.DummyOperator()
+
+    # take first step
+    bundle.solver(operator, [0.75], 1.0).integrate()
+
+    # restart
+    prev_res = openmc.deplete.Results(
+        operator.output_dir / "depletion_results.h5")
+    operator = dummy_operator.DummyOperator(prev_res)
+
+    # if continue run happens, test passes
+    bundle.solver(operator, [0.75, 0.75], [1.0, 1.0], continue_timesteps=True).integrate()
+
+@pytest.mark.parametrize("scheme", dummy_operator.SCHEMES)
+def test_mismatched_initial_times(run_in_tmpdir, scheme):
+    """Test to ensure that a continue run with different initial steps is properly caught"""
+
+    # set up the problem
+
+    bundle = dummy_operator.SCHEMES[scheme]
+
+    operator = dummy_operator.DummyOperator()
+
+    # take first step
+    bundle.solver(operator, [0.75, 0.75], [1.0, 1.0]).integrate()
+
+    # restart
+    prev_res = openmc.deplete.Results(
+        operator.output_dir / "depletion_results.h5")
+    operator = dummy_operator.DummyOperator(prev_res)
+
+    with pytest.raises(
+        ValueError,
+        match = "You are attempting to continue a run in which the previous "
+                "results do not have the same initial steps as those provided "
+                "to the Integrator. Please make sure you are using the correct "
+                "timesteps, powers or power densities, and previous results file.",
+    ):
+        bundle.solver(
+            operator, [0.75, 0.5, 0.75], [1.0, 1.0, 1.0], continue_timesteps=True
+        ).integrate()
+
+@pytest.mark.parametrize("scheme", dummy_operator.SCHEMES)
+def test_mismatched_initial_source_rates(run_in_tmpdir, scheme):
+    """Test to ensure that a continue run with different initial steps is properly caught"""
+
+    # set up the problem
+
+    bundle = dummy_operator.SCHEMES[scheme]
+
+    operator = dummy_operator.DummyOperator()
+
+    # take first step
+    bundle.solver(operator, [0.75, 0.75], [1.0, 1.0]).integrate()
+
+    # restart
+    prev_res = openmc.deplete.Results(
+        operator.output_dir / "depletion_results.h5")
+    operator = dummy_operator.DummyOperator(prev_res)
+
+    with pytest.raises(
+        ValueError,
+        match = "You are attempting to continue a run in which the previous "
+                "results do not have the same initial steps as those provided "
+                "to the Integrator. Please make sure you are using the correct "
+                "timesteps, powers or power densities, and previous results file.",
+    ):
+        bundle.solver(
+            operator, [0.75, 0.75, 0.75], [1.0, 2.0, 1.0], continue_timesteps=True
+        ).integrate()