Fix force group 31

wrappers/python/src/swig_doxygen/swig_lib/python/extend.i

+%inline %{
+    typedef int bitmask32t;
+%}
+
+%typemap(in) bitmask32t %{
+    $1 = 0;
+#if PY_VERSION_HEX >= 0x03000000
+    if (PyLong_Check($input)) {
+        unsigned long u = PyLong_AsUnsignedLongMask($input);
+#else
+    if (PyInt_Check($input)) {
+        unsigned long u = PyInt_AsUnsignedLongMask($input);
+#endif
+        // 64-bit Windows has 32-bit longs, but other platforms have
+        // 64-bit longs
+        $1 = u & 0xffffffff;
+    } else {
+        PyErr_SetString(PyExc_ValueError, "in method $symname, argument $argnum could not be converted to type $type");
+        SWIG_fail;
+    }
+%}
+
+
+
 %extend OpenMM::Context {
   PyObject *_getStateAsLists(int getPositions,
                             int getVelocities,
@@ -5,7 +29,7 @@
                             int getEnergy,
                             int getParameters,
                             int enforcePeriodic,
-                            int groups) {
+                            bitmask32t groups) {
     State state;
     PyThreadState* _savePythonThreadState = PyEval_SaveThread();
     int types = 0;
@@ -36,15 +60,9 @@
                  enforcePeriodicBox=False,
                  groups=-1):
         """
-        getState(self,
-                 getPositions = False,
-                 getVelocities = False,
-                 getForces = False,
-                 getEnergy = False,
-                 getParameters = False,
-                 enforcePeriodicBox = False,
-                 groups = -1)
-              -> State
+        getState(self, getPositions=False, getVelocities=False, getForces=False,
+                 getEnergy=False, getParameters=False, enforcePeriodicBox=False,
+                 groups=-1) -> State
 
         Get a State object recording the current state information stored in this context.
 

wrappers/python/tests/TestForceGroups.py

@@ -20,7 +20,7 @@ class TestForceGroups(unittest.TestCase):
         self.context = context
 
     def test1(self):
-        n = 31  # Should be 32, but github issue #1198
+        n = 32
         for (i,j) in itertools.combinations(range(n), 2):
             groups = 1<<i | 1<<j
             e_0 = self.context.getState(getEnergy=True, groups=groups).getPotentialEnergy()._value
@@ -34,6 +34,12 @@ class TestForceGroups(unittest.TestCase):
             # groups must be an int or set
             self.context.getState(getEnergy=True, groups=(1, 2))
 
+    def test3(self):
+        e_0 = self.context.getState(getEnergy=True, groups=-1).getPotentialEnergy()._value
+        e_ref = sum(range(32))
+        self.assertEqual(e_0, e_ref)
+
+
 if __name__ == '__main__':
     unittest.main()