Remove default and kludgey way to half-support backwards compatibility.

Update the Python application layer to use both force constants when building
the AmoebaStretchBendForce.

plugins/amoeba/openmmapi/include/openmm/AmoebaStretchBendForce.h

@@ -76,7 +76,7 @@ public:
      * @return the index of the stretch-bend that was added
      */
     int addStretchBend(int particle1, int particle2, int particle3, double lengthAB,  double lengthCB, double angle,
-                       double k1, double k2=-1.0);
+                       double k1, double k2);
 
     /**
      * Get the force field parameters for a stretch-bend term.
@@ -108,7 +108,7 @@ public:
      * @param k2            the force constant of the product of bond bc and angle a-b-c (optional, default is the same as k1)
      */
     void setStretchBendParameters(int index, int particle1, int particle2, int particle3, 
-                                  double lengthAB,  double lengthCB, double angle, double k1, double k2=-1.0 );
+                                  double lengthAB,  double lengthCB, double angle, double k1, double k2);
     /**
      * Update the per-stretch-bend term parameters in a Context to match those stored in this Force object.  This method provides
      * an efficient method to update certain parameters in an existing Context without needing to reinitialize it.

plugins/amoeba/openmmapi/src/AmoebaStretchBendForce.cpp

@@ -41,7 +41,6 @@ AmoebaStretchBendForce::AmoebaStretchBendForce() {
 
 int AmoebaStretchBendForce::addStretchBend(int particle1, int particle2, int particle3,
                                            double lengthAB,  double lengthCB, double angle, double k1, double k2) {
-    if (k2 == -1.0) k2 = k1;
     stretchBends.push_back(StretchBendInfo(particle1, particle2, particle3, lengthAB,  lengthCB, angle, k1, k2));
     return stretchBends.size()-1;
 }
@@ -67,10 +66,7 @@ void AmoebaStretchBendForce::setStretchBendParameters(int index, int particle1,
     stretchBends[index].lengthCB   = lengthCB;
     stretchBends[index].angle      = angle;
     stretchBends[index].k1         = k1;
-    if (k2 == -1.0)
-        stretchBends[index].k2     = k1;
-    else
-        stretchBends[index].k2     = k2;
+    stretchBends[index].k2         = k2;
 }
 
 ForceImpl* AmoebaStretchBendForce::createImpl() const {

plugins/amoeba/platforms/cuda/tests/TestCudaAmoebaStretchBendForce.cpp

@@ -276,7 +276,7 @@ void testOneStretchBend( FILE* log ) {
     //double kStretchBend     = 0.750491578E-01;
     double kStretchBend     = 1.0;
 
-    amoebaStretchBendForce->addStretchBend(0, 1, 2, abLength, cbLength, angleStretchBend, kStretchBend );
+    amoebaStretchBendForce->addStretchBend(0, 1, 2, abLength, cbLength, angleStretchBend, kStretchBend, kStretchBend );
 
     system.addForce(amoebaStretchBendForce);
     Context context(system, integrator, Platform::getPlatformByName( "CUDA"));
@@ -292,7 +292,7 @@ void testOneStretchBend( FILE* log ) {
     
     // Try changing the stretch-bend parameters and make sure it's still correct.
     
-    amoebaStretchBendForce->setStretchBendParameters(0, 0, 1, 2, 1.1*abLength, 1.2*cbLength, 1.3*angleStretchBend, 1.4*kStretchBend);
+    amoebaStretchBendForce->setStretchBendParameters(0, 0, 1, 2, 1.1*abLength, 1.2*cbLength, 1.3*angleStretchBend, 1.4*kStretchBend, 1.4*kStretchBend);
     bool exceptionThrown = false;
     try {
         // This should throw an exception.

plugins/amoeba/platforms/reference/tests/TestReferenceAmoebaStretchBendForce.cpp

@@ -275,7 +275,7 @@ void testOneStretchBend( FILE* log ) {
     //double kStretchBend     = 0.750491578E-01;
     double kStretchBend     = 1.0;
 
-    amoebaStretchBendForce->addStretchBend(0, 1, 2, abLength, cbLength, angleStretchBend, kStretchBend );
+    amoebaStretchBendForce->addStretchBend(0, 1, 2, abLength, cbLength, angleStretchBend, kStretchBend, kStretchBend );
 
     system.addForce(amoebaStretchBendForce);
     ASSERT(!amoebaStretchBendForce->usesPeriodicBoundaryConditions());
@@ -293,7 +293,7 @@ void testOneStretchBend( FILE* log ) {
     
     // Try changing the stretch-bend parameters and make sure it's still correct.
     
-    amoebaStretchBendForce->setStretchBendParameters(0, 0, 1, 2, 1.1*abLength, 1.2*cbLength, 1.3*angleStretchBend, 1.4*kStretchBend);
+    amoebaStretchBendForce->setStretchBendParameters(0, 0, 1, 2, 1.1*abLength, 1.2*cbLength, 1.3*angleStretchBend, 1.4*kStretchBend, 1.4*kStretchBend);
     bool exceptionThrown = false;
     try {
         // This should throw an exception.

wrappers/python/simtk/openmm/app/forcefield.py

@@ -3086,7 +3086,7 @@ class AmoebaStretchBendGenerator:
                        raise ValueError(outputString)
 
                     else:
-                        force.addStretchBend(angle[0], angle[1], angle[2], bondAB, bondCB, angleDict['idealAngle']/radian, self.k1[i])
+                        force.addStretchBend(angle[0], angle[1], angle[2], bondAB, bondCB, angleDict['idealAngle']/radian, self.k1[i], self.k2[i])
 
                     break