Bug fix to selection of Ewald parameters

platforms/cuda/src/CudaKernels.cpp

@@ -310,9 +310,15 @@ void CudaCalcNonbondedForceKernel::initialize(const System& system, const Nonbon
             double my = boxVectors[1][1]/force.getCutoffDistance();
             double mz = boxVectors[2][2]/force.getCutoffDistance();
             double pi = 3.1415926535897932385;
-            int kmaxx = std::ceil(-(mx/pi)*std::log(ewaldErrorTol));;
-            int kmaxy = std::ceil(-(my/pi)*std::log(ewaldErrorTol));;
-            int kmaxz = std::ceil(-(mz/pi)*std::log(ewaldErrorTol));;
+            int kmaxx = std::ceil(-(mx/pi)*std::log(ewaldErrorTol));
+            int kmaxy = std::ceil(-(my/pi)*std::log(ewaldErrorTol));
+            int kmaxz = std::ceil(-(mz/pi)*std::log(ewaldErrorTol));
+            if (kmaxx%2 == 0)
+                kmaxx++;
+            if (kmaxy%2 == 0)
+                kmaxy++;
+            if (kmaxz%2 == 0)
+                kmaxz++;
             gpuSetEwaldParameters(gpu, alpha, kmaxx, kmaxy, kmaxz);
             method = EWALD;
         }

platforms/reference/src/ReferenceKernels.cpp

@@ -402,6 +402,12 @@ void ReferenceCalcNonbondedForceKernel::initialize(const System& system, const N
         kmax[0] = std::ceil(-(mx/pi)*std::log(ewaldErrorTol));
         kmax[1] = std::ceil(-(my/pi)*std::log(ewaldErrorTol));
         kmax[2] = std::ceil(-(mz/pi)*std::log(ewaldErrorTol));
+        if (kmax[0]%2 == 0)
+            kmax[0]++;
+        if (kmax[1]%2 == 0)
+            kmax[1]++;
+        if (kmax[2]%2 == 0)
+            kmax[2]++;
     }
 }