Fix/issue 708 (#710)

* add test that will fail until we have a fix

* check to see if real time analysis is none before check if it has been set

* see if this fixes issues on osx

* lets see if upstream has fixed the issue

* I will just fix this in another PR

openmmtools/multistate/multistatesampler.py

@@ -592,9 +592,11 @@ def create(self, thermodynamic_states: list, sampler_states, storage,
 
         # Make sure online analysis interval is a multiples of the reporter's checkpoint interval
         # this avoids having redundant iteration information in the real time yaml files
-        if self.online_analysis_interval % self._reporter.checkpoint_interval != 0:
-            raise ValueError(f"Online analysis interval: {self.online_analysis_interval}, must be a "
-                             f"multiple of the checkpoint interval: {self._reporter.checkpoint_interval}")
+        # only check if self.online_analysis_interval is set
+        if self.online_analysis_interval:
+            if self.online_analysis_interval % self._reporter.checkpoint_interval != 0:
+                raise ValueError(f"Online analysis interval: {self.online_analysis_interval}, must be a "
+                                 f"multiple of the checkpoint interval: {self._reporter.checkpoint_interval}")
 
         # Make sure sampler_states is an iterable of SamplerStates.
         if isinstance(sampler_states, states.SamplerState):

openmmtools/tests/test_sampling.py

@@ -16,10 +16,12 @@
 import contextlib
 import copy
 import inspect
+import math
 import os
 import pickle
 import shutil
 import sys
+import tempfile
 from io import StringIO
 
 import numpy as np
@@ -35,8 +37,7 @@
 import mpiplus
 
 import openmmtools as mmtools
-from openmmtools import cache
-from openmmtools import testsystems
+from openmmtools import cache, testsystems, states, mcmc
 from openmmtools.multistate import MultiStateReporter
 from openmmtools.multistate import MultiStateSampler, MultiStateSamplerAnalyzer
 from openmmtools.multistate import ReplicaExchangeSampler, ReplicaExchangeAnalyzer
@@ -1595,7 +1596,24 @@ def test_real_time_analysis_yaml(self):
             assert len(yaml_contents) == expected_yaml_entries, \
                 "Expected yaml entries do not match the actual number entries in the file."
 
-
+def test_real_time_analysis_can_be_none():
+    """Test if real time analysis can be done"""
+    testsystem = testsystems.AlanineDipeptideImplicit()
+    n_replicas = 3
+    T_min = 298.0 * unit.kelvin  # Minimum temperature.
+    T_max = 600.0 * unit.kelvin  # Maximum temperature.
+    temperatures = [T_min + (T_max - T_min) * (math.exp(float(i) / float(n_replicas-1)) - 1.0) / (math.e - 1.0)
+                    for i in range(n_replicas)]
+    temperatures = [T_min + (T_max - T_min) * (math.exp(float(i) / float(n_replicas-1)) - 1.0) / (math.e - 1.0)
+                    for i in range(n_replicas)]
+    thermodynamic_states = [states.ThermodynamicState(system=testsystem.system, temperature=T)
+                            for T in temperatures]
+    move = mcmc.GHMCMove(timestep=2.0*unit.femtoseconds, n_steps=50)
+    simulation = MultiStateSampler(mcmc_moves=move, number_of_iterations=2, online_analysis_interval=None)
+    storage_path = tempfile.NamedTemporaryFile(delete=False).name + '.nc'
+    reporter = MultiStateReporter(storage_path, checkpoint_interval=1)
+    simulation.create(thermodynamic_states=thermodynamic_states,
+                      sampler_states=states.SamplerState(testsystem.positions), storage=reporter)
 #############
 
 class TestExtraSamplersMultiStateSampler(TestMultiStateSampler):