Trivial changes to AMOEBA plugin.

o Variable renaming in multipole electrostatics code, to avoid confusion.
o CUDA test case only runs finite difference test for the double precision test.

plugins/amoeba/platforms/cuda/src/kernels/multipoleElectrostatics.cu

@@ -336,7 +336,7 @@ __device__ void computeOneInteraction(AtomData& atom1, AtomData& atom2, bool has
     iEIY -= eCoef*(qiUinpI.y*qiUindJ.x + qiUindI.y*qiUinpJ.x);
     iEJY -= eCoef*(qiUinpJ.y*qiUindI.x + qiUindJ.y*qiUinpI.x);
     fIZ += dCoef*(qiUinpI.x*qiUindJ.x + qiUindI.x*qiUinpJ.x);
-    fIZ += dCoef*(qiUinpJ.x*qiUindI.x + qiUindJ.x*qiUinpI.x);
+    fJZ += dCoef*(qiUinpJ.x*qiUindI.x + qiUindJ.x*qiUinpI.x);
     // Uind-Uind terms (m=1)
     eCoef = 2*rInvVec[3]*thole_d1;
     dCoef = -3*rInvVec[4]*dthole_d1;
@@ -345,7 +345,7 @@ __device__ void computeOneInteraction(AtomData& atom1, AtomData& atom2, bool has
     iEIY += eCoef*(qiUinpI.x*qiUindJ.y + qiUindI.x*qiUinpJ.y);
     iEJY += eCoef*(qiUinpJ.x*qiUindI.y + qiUindJ.x*qiUinpI.y);
     fIZ += dCoef*(qiUinpI.y*qiUindJ.y + qiUindI.y*qiUinpJ.y + qiUinpI.z*qiUindJ.z + qiUindI.z*qiUinpJ.z);
-    fIZ += dCoef*(qiUinpJ.y*qiUindI.y + qiUindJ.y*qiUinpI.y + qiUinpJ.z*qiUindI.z + qiUindJ.z*qiUinpI.z);
+    fJZ += dCoef*(qiUinpJ.y*qiUindI.y + qiUindJ.y*qiUinpI.y + qiUinpJ.z*qiUindI.z + qiUindJ.z*qiUinpI.z);
 #endif
 
     // The quasi-internal frame forces and torques.  Note that the induced torque intermediates are

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

@@ -284,8 +284,10 @@ vector<Vec3> setupWaterDimer(System& system,  AmoebaMultipoleForce* amoebaMultip
 
 static void check_finite_differences(vector<Vec3> analytic_forces, Context &context, vector<Vec3> positions)
 {
-    // Take a small step in the direction of the energy gradient and see whether the potential energy changes by the expected amount.
+    // This is a bad test in single precision, due to roundoff errors; skip it in this case.
+    if(Platform::getPlatformByName("CUDA").getPropertyValue(context, "Precision") != "double") return;
 
+    // Take a small step in the direction of the energy gradient and see whether the potential energy changes by the expected amount.
     double norm = 0.0;
     for (int i = 0; i < (int) analytic_forces.size(); ++i)
         norm += analytic_forces[i].dot(analytic_forces[i]);

plugins/amoeba/platforms/reference/src/SimTKReference/AmoebaReferenceMultipoleForce.cpp

@@ -1509,7 +1509,7 @@ RealOpenMM AmoebaReferenceMultipoleForce::calculateElectrostaticPairIxn(const Mu
         iEIY -= eCoef*(qiUinpI[1]*qiUindJ[0] + qiUindI[1]*qiUinpJ[0]);
         iEJY -= eCoef*(qiUinpJ[1]*qiUindI[0] + qiUindJ[1]*qiUinpI[0]);
         fIZ += dCoef*(qiUinpI[0]*qiUindJ[0] + qiUindI[0]*qiUinpJ[0]);
-        fIZ += dCoef*(qiUinpJ[0]*qiUindI[0] + qiUindJ[0]*qiUinpI[0]);
+        fJZ += dCoef*(qiUinpJ[0]*qiUindI[0] + qiUindJ[0]*qiUinpI[0]);
         // Uind-Uind terms (m=1)
         eCoef = 2.0*rInvVec[3]*uScale*thole_d1;
         dCoef = -3.0*rInvVec[4]*uScale*dthole_d1;
@@ -1518,7 +1518,7 @@ RealOpenMM AmoebaReferenceMultipoleForce::calculateElectrostaticPairIxn(const Mu
         iEIY += eCoef*(qiUinpI[0]*qiUindJ[1] + qiUindI[0]*qiUinpJ[1]);
         iEJY += eCoef*(qiUinpJ[0]*qiUindI[1] + qiUindJ[0]*qiUinpI[1]);
         fIZ += dCoef*(qiUinpI[1]*qiUindJ[1] + qiUindI[1]*qiUinpJ[1] + qiUinpI[2]*qiUindJ[2] + qiUindI[2]*qiUinpJ[2]);
-        fIZ += dCoef*(qiUinpJ[1]*qiUindI[1] + qiUindJ[1]*qiUinpI[1] + qiUinpJ[2]*qiUindI[2] + qiUindJ[2]*qiUinpI[2]);
+        fJZ += dCoef*(qiUinpJ[1]*qiUindI[1] + qiUindJ[1]*qiUinpI[1] + qiUinpJ[2]*qiUindI[2] + qiUindJ[2]*qiUinpI[2]);
     }
 
     // The quasi-internal frame forces and torques.  Note that the induced torque intermediates are
@@ -6802,7 +6802,7 @@ RealOpenMM AmoebaReferencePmeMultipoleForce::calculatePmeDirectElectrostaticPair
         iEIY -= eCoef*(qiUinpI[1]*qiUindJ[0] + qiUindI[1]*qiUinpJ[0]);
         iEJY -= eCoef*(qiUinpJ[1]*qiUindI[0] + qiUindJ[1]*qiUinpI[0]);
         fIZ += dCoef*(qiUinpI[0]*qiUindJ[0] + qiUindI[0]*qiUinpJ[0]);
-        fIZ += dCoef*(qiUinpJ[0]*qiUindI[0] + qiUindJ[0]*qiUinpI[0]);
+        fJZ += dCoef*(qiUinpJ[0]*qiUindI[0] + qiUindJ[0]*qiUinpI[0]);
         // Uind-Uind terms (m=1)
         eCoef = 2.0*rInvVec[3]*(uScale*thole_d1 + bVec[3] - twoThirds*alphaRVec[3]*X);
         dCoef = -3.0*rInvVec[4]*(uScale*dthole_d1 + bVec[3]);
@@ -6811,7 +6811,7 @@ RealOpenMM AmoebaReferencePmeMultipoleForce::calculatePmeDirectElectrostaticPair
         iEIY += eCoef*(qiUinpI[0]*qiUindJ[1] + qiUindI[0]*qiUinpJ[1]);
         iEJY += eCoef*(qiUinpJ[0]*qiUindI[1] + qiUindJ[0]*qiUinpI[1]);
         fIZ += dCoef*(qiUinpI[1]*qiUindJ[1] + qiUindI[1]*qiUinpJ[1] + qiUinpI[2]*qiUindJ[2] + qiUindI[2]*qiUinpJ[2]);
-        fIZ += dCoef*(qiUinpJ[1]*qiUindI[1] + qiUindJ[1]*qiUinpI[1] + qiUinpJ[2]*qiUindI[2] + qiUindJ[2]*qiUinpI[2]);
+        fJZ += dCoef*(qiUinpJ[1]*qiUindI[1] + qiUindJ[1]*qiUinpI[1] + qiUinpJ[2]*qiUindI[2] + qiUindJ[2]*qiUinpI[2]);
     }
 
     // The quasi-internal frame forces and torques.  Note that the induced torque intermediates are