Add stop_after_walltime and stop_on_interrupt (NanoComp#860)

* Add stop_after_walltime and stop_on_interrupt

* Fix doc typo [ci skip]

* Let until take a list of stopping conditions

* Fix docs for run

doc/docs/Python_User_Interface.md

@@ -1530,11 +1530,11 @@ A common point of confusion is described in [The Run Function Is Not A Loop](The
 
 **`run(step_functions..., until=condition/time)`**
 —
-Run the simulation until a certain time or condition, calling the given step functions (if any) at each timestep. The keyword argument `until` is *either* a number, in which case it is an additional time (in Meep units) to run for, *or* it is a function (of no arguments) which returns `True` when the simulation should stop.
+Run the simulation until a certain time or condition, calling the given step functions (if any) at each timestep. The keyword argument `until` is *either* a number, in which case it is an additional time (in Meep units) to run for, *or* it is a function (of no arguments) which returns `True` when the simulation should stop. `until` can also be a list of stopping conditions which may include a number and additional functions.
 
 **`run(step_functions..., until_after_sources=condition/time)`**
 —
-Run the simulation until all sources have turned off, calling the given step functions (if any) at each timestep. The keyword argument `until_after_sources` is either a number, in which case it is an *additional* time (in Meep units) to run for after the sources are off, *or* it is a function (of no arguments). In the latter case, the simulation runs until the sources are off *and* `condition` returns `True`.
+Run the simulation until all sources have turned off, calling the given step functions (if any) at each timestep. The keyword argument `until_after_sources` is either a number, in which case it is an *additional* time (in Meep units) to run for after the sources are off, *or* it is a function (of no arguments). In the latter case, the simulation runs until the sources are off *and* `condition` returns `True`. Like `until` above, `until_after_sources` can take a list of stopping conditions.
 
 In particular, a useful value for `until_after_sources` or `until` is often `stop_when_field_decayed`, which is demonstrated in [Tutorial/Basics](Python_Tutorials/Basics.md#transmittance-spectrum-of-a-waveguide-bend):
 
@@ -1544,6 +1544,14 @@ Return a `condition` function, suitable for passing to `until`/`until_after_sour
 
 Note that, if you make `decay_by` very small, you may need to increase the `cutoff` property of your source(s), to decrease the amplitude of the small high-frequency components that are excited when the source turns off. High frequencies near the [Nyquist frequency](https://en.wikipedia.org/wiki/Nyquist_frequency) of the grid have slow group velocities and are absorbed poorly by [PML](Perfectly_Matched_Layer.md).
 
+**`stop_after_walltime(t)`**
+—
+Return a `condition` function, suitable for passing to `until`. Stops the simulation after `t` seconds of wall time have passed.
+
+**`stop_on_interrupt()`**
+—
+Return a `condition` function, suitable for passing to `until`. Instead of terminating when receiving a SIGINT or SIGTERM signal from the system, the simulation will abort time stepping and continue executing any code that follows the `run` function (e.g., outputting fields).
+
 Finally, another run function, useful for computing ω(**k**) band diagrams, is:
 
 **`run_k_points(T, k_points)`**

python/meep.i

@@ -1489,6 +1489,8 @@ PyObject *_get_array_slice_dimensions(meep::fields *f, const meep::volume &where
         scale_flux_fields,
         scale_force_fields,
         scale_near2far_fields,
+        stop_after_walltime,
+        stop_on_interrupt,
         stop_when_fields_decayed,
         synchronized_magnetic,
         to_appended,

python/simulation.py

@@ -5,6 +5,7 @@
 import numbers
 import os
 import re
+import signal
 import subprocess
 import sys
 import warnings
@@ -1232,19 +1233,25 @@ def _run_until(self, cond, step_funcs):
         if self.fields is None:
             self.init_sim()
 
-        if isinstance(cond, numbers.Number):
-            stop_time = cond
-            t0 = self.round_time()
+        if not isinstance(cond, list):
+            cond = [cond]
 
-            def stop_cond(sim):
-                return sim.round_time() >= t0 + stop_time
+        for i in range(len(cond)):
+            if isinstance(cond[i], numbers.Number):
+                stop_time = cond[i]
+                t0 = self.round_time()
 
-            cond = stop_cond
+                def stop_cond(sim):
+                    return sim.round_time() >= t0 + stop_time
 
-            step_funcs = list(step_funcs)
-            step_funcs.append(display_progress(t0, t0 + stop_time, self.progress_interval))
+                cond[i] = stop_cond
 
-        while not cond(self):
+                step_funcs = list(step_funcs)
+                step_funcs.append(display_progress(t0, t0 + stop_time, self.progress_interval))
+            else:
+                assert callable(cond[i]), "Stopping condition {} is not an integer or a function".format(cond[i])
+
+        while not any([x(self) for x in cond]):
             for func in step_funcs:
                 _eval_step_func(self, func, 'step')
             self.fields.step()
@@ -1266,16 +1273,20 @@ def _run_sources_until(self, cond, step_funcs):
         if self.fields is None:
             self.init_sim()
 
-        ts = self.fields.last_source_time()
+        if not isinstance(cond, list):
+            cond = [cond]
 
-        if isinstance(cond, numbers.Number):
-            new_cond = (ts - self.round_time()) + cond
-        else:
-            def f(sim):
-                return cond(sim) and sim.round_time() >= ts
-            new_cond = f
+        ts = self.fields.last_source_time()
+        new_conds = []
+        for i in range(len(cond)):
+            if isinstance(cond[i], numbers.Number):
+                new_conds.append((ts - self.round_time()) + cond[i])
+            else:
+                def f(sim):
+                    return cond[i](sim) and sim.round_time() >= ts
+                new_conds.append(f)
 
-        self._run_until(new_cond, step_funcs)
+        self._run_until(new_conds, step_funcs)
 
     def _run_sources(self, step_funcs):
         self._run_sources_until(self, 0, step_funcs)
@@ -2433,6 +2444,31 @@ def _stop(sim):
     return _stop
 
 
+def stop_after_walltime(t):
+    start = mp.wall_time()
+    def _stop_after_walltime(sim):
+        if mp.wall_time() - start > t:
+            return True
+        return False
+    return _stop_after_walltime
+
+
+def stop_on_interrupt():
+    shutting_down = [False]
+
+    def _signal_handler(sig, frame):
+        print("WARNING: System requested termination. Time stepping aborted.")
+        shutting_down[0] = True
+
+    signal.signal(signal.SIGINT, _signal_handler)
+    signal.signal(signal.SIGTERM, _signal_handler)
+
+    def _stop(sim):
+        return shutting_down[0]
+
+    return _stop
+
+
 def synchronized_magnetic(*step_funcs):
     def _sync(sim, todo):
         sim.fields.synchronize_magnetic_fields()

python/tests/simulation.py

@@ -626,5 +626,6 @@ def mat_func(p):
         _check(mp.Medium(), False)
         _check(mat_func, False)
 
+
 if __name__ == '__main__':
     unittest.main()