getState() can specify which force groups to use

openmmapi/include/openmm/Context.h

@@ -123,8 +123,10 @@ public:
      * @param enforcePeriodicBox if false, the position of each particle will be whatever position
      * is stored in the Context, regardless of periodic boundary conditions.  If true, particle
      * positions will be translated so the center of every molecule lies in the same periodic box.
+     * @param groups a set of bit flags for which force groups to include when computing forces
+     * and energies.  Group i will be included if (groups&(1<<i)) != 0.  The default value includes all groups.
      */
-    State getState(int types, bool enforcePeriodicBox=false) const;
+    State getState(int types, bool enforcePeriodicBox=false, int groups=0xFFFFFFFF) const;
     /**
      * Set the current time of the simulation (in picoseconds).
      */

openmmapi/src/Context.cpp

@@ -78,7 +78,7 @@ Platform& Context::getPlatform() {
     return impl->getPlatform();
 }
 
-State Context::getState(int types, bool enforcePeriodicBox) const {
+State Context::getState(int types, bool enforcePeriodicBox, int groups) const {
     State state(impl->getTime(), impl->getSystem().getNumParticles(), types);
     Vec3 periodicBoxSize[3];
     impl->getPeriodicBoxVectors(periodicBoxSize[0], periodicBoxSize[1], periodicBoxSize[2]);
@@ -86,7 +86,7 @@ State Context::getState(int types, bool enforcePeriodicBox) const {
     bool includeForces = types&State::Forces;
     bool includeEnergy = types&State::Energy;
     if (includeForces || includeEnergy) {
-        double energy = impl->calcForcesAndEnergy(includeForces, includeEnergy);
+        double energy = impl->calcForcesAndEnergy(includeForces, includeEnergy, groups);
         if (includeEnergy)
             state.setEnergy(impl->calcKineticEnergy(), energy);
         if (includeForces)

platforms/opencl/tests/TestOpenCLCustomIntegrator.cpp

@@ -568,6 +568,19 @@ void testForceGroups() {
     ASSERT_EQUAL_VEC(Vec3(138.935456*0.2*0.2/4.0, 0, 0), f2[1], 1e-5);
     ASSERT_EQUAL_VEC(f1[0]+f2[0], f[0], 1e-5);
     ASSERT_EQUAL_VEC(f1[1]+f2[1], f[1], 1e-5);
+    
+    // Make sure they also match the values returned by the Context.
+    
+    vector<Vec3> c, c1, c2;
+    c = context.getState(State::Forces, false).getForces();
+    c1 = context.getState(State::Forces, false, 2).getForces();
+    c2 = context.getState(State::Forces, false, 4).getForces();
+    ASSERT_EQUAL_VEC(f[0], c[0], 1e-5);
+    ASSERT_EQUAL_VEC(f[1], c[1], 1e-5);
+    ASSERT_EQUAL_VEC(f1[0], c1[0], 1e-5);
+    ASSERT_EQUAL_VEC(f1[1], c1[1], 1e-5);
+    ASSERT_EQUAL_VEC(f2[0], c2[0], 1e-5);
+    ASSERT_EQUAL_VEC(f2[1], c2[1], 1e-5);
 }
 
 /**

platforms/reference/tests/TestReferenceCustomIntegrator.cpp

@@ -553,6 +553,19 @@ void testForceGroups() {
     ASSERT_EQUAL_VEC(Vec3(138.935456*0.2*0.2/4.0, 0, 0), f2[1], 1e-5);
     ASSERT_EQUAL_VEC(f1[0]+f2[0], f[0], 1e-5);
     ASSERT_EQUAL_VEC(f1[1]+f2[1], f[1], 1e-5);
+    
+    // Make sure they also match the values returned by the Context.
+    
+    vector<Vec3> c, c1, c2;
+    c = context.getState(State::Forces, false).getForces();
+    c1 = context.getState(State::Forces, false, 2).getForces();
+    c2 = context.getState(State::Forces, false, 4).getForces();
+    ASSERT_EQUAL_VEC(f[0], c[0], 1e-5);
+    ASSERT_EQUAL_VEC(f[1], c[1], 1e-5);
+    ASSERT_EQUAL_VEC(f1[0], c1[0], 1e-5);
+    ASSERT_EQUAL_VEC(f1[1], c1[1], 1e-5);
+    ASSERT_EQUAL_VEC(f2[0], c2[0], 1e-5);
+    ASSERT_EQUAL_VEC(f2[1], c2[1], 1e-5);
 }
 
 /**