pybamm-team#976 added extrapolation warnings

pybamm/solvers/base_solver.py

@@ -8,6 +8,7 @@
 import numpy as np
 import sys
 import itertools
+import warnings
 
 
 class BaseSolver(object):
@@ -30,6 +31,8 @@ class BaseSolver(object):
         specified by 'root_method' (e.g. "lm", "hybr", ...)
     root_tol : float, optional
         The tolerance for the initial-condition solver (default is 1e-6).
+    extrap_tol : float, optional
+        The tolerance to assert whether extrapolation occurs or not. Default is 0.
     """
 
     def __init__(
@@ -39,13 +42,15 @@ def __init__(
         atol=1e-6,
         root_method=None,
         root_tol=1e-6,
+        extrap_tol=0,
         max_steps="deprecated",
     ):
         self._method = method
         self._rtol = rtol
         self._atol = atol
         self.root_tol = root_tol
         self.root_method = root_method
+        self.extrap_tol = extrap_tol
         if max_steps != "deprecated":
             raise ValueError(
                 "max_steps has been deprecated, and should be set using the "
@@ -706,6 +711,16 @@ def solve(
         solution.timescale_eval = model.timescale_eval
         solution.length_scales_eval = model.length_scales_eval
 
+        # Check if extrapolation occurred
+        extrapolation = self.check_extrapolation(solution, model.events)
+        if extrapolation:
+            warnings.warn(
+                "While solving {} extrapolation occurred for {}".format(
+                    model.name, extrapolation
+                ),
+                pybamm.SolverWarning,
+            )
+
         # Identify the event that caused termination
         termination = self.get_termination_reason(solution, model.events)
 
@@ -861,6 +876,16 @@ def step(
         solution.timescale_eval = temp_timescale_eval
         solution.length_scales_eval = temp_length_scales_eval
 
+        # Check if extrapolation occurred
+        extrapolation = self.check_extrapolation(solution, model.events)
+        if extrapolation:
+            warnings.warn(
+                "While solving {} extrapolation occurred for {}".format(
+                    model.name, extrapolation
+                ),
+                pybamm.SolverWarning,
+            )
+
         # Identify the event that caused termination
         termination = self.get_termination_reason(solution, model.events)
 
@@ -930,6 +955,48 @@ def get_termination_reason(self, solution, events):
 
             return "the termination event '{}' occurred".format(termination_event)
 
+    def check_extrapolation(self, solution, events):
+        """
+        Check if extrapolation occurred for any of the interpolants. Note that with the
+        current approach (evaluating all the events at the solution times) some
+        extrapolations might not be found if they only occurred for a small period of
+        time.
+
+        Parameters
+        ----------
+        solution : :class:`pybamm.Solution`
+            The solution object
+        events : dict
+            Dictionary of events
+        """
+        extrap_events = {}
+
+        for event in events:
+            if event.event_type == pybamm.EventType.INTERPOLANT_EXTRAPOLATION:
+                extrap_events[event.name] = False
+
+        try:
+            y_full = solution.y.full()
+        except AttributeError:
+            y_full = solution.y
+
+        for event in events:
+            if event.event_type == pybamm.EventType.INTERPOLANT_EXTRAPOLATION:
+                if (
+                    event.expression.evaluate(
+                        solution.t,
+                        y_full,
+                        inputs={k: v for k, v in solution.inputs.items()},
+                    )
+                    < self.extrap_tol
+                ).any():
+                    extrap_events[event.name] = True
+
+        # Add the event dictionaryto the solution object
+        solution.extrap_events = extrap_events
+
+        return [k for k, v in extrap_events.items() if v]
+
     def _set_up_ext_and_inputs(self, model, external_variables, inputs):
         "Set up external variables and input parameters"
         inputs = inputs or {}