Reduced size of PME grid, since it was being made unnecessarily large for the requested accuracy.

openmmapi/src/NonbondedForceImpl.cpp

@@ -150,9 +150,9 @@ void NonbondedForceImpl::calcPMEParameters(const System& system, const Nonbonded
     system.getDefaultPeriodicBoxVectors(boxVectors[0], boxVectors[1], boxVectors[2]);
     double tol = force.getEwaldErrorTolerance();
     alpha = (1.0/force.getCutoffDistance())*std::sqrt(-log(2.0*tol));
-    xsize = (int) ceil(alpha*boxVectors[0][0]/pow(0.5*tol, 0.2));
-    ysize = (int) ceil(alpha*boxVectors[1][1]/pow(0.5*tol, 0.2));
-    zsize = (int) ceil(alpha*boxVectors[2][2]/pow(0.5*tol, 0.2));
+    xsize = (int) ceil(2*alpha*boxVectors[0][0]/(3*pow(tol, 0.2)));
+    ysize = (int) ceil(2*alpha*boxVectors[1][1]/(3*pow(tol, 0.2)));
+    zsize = (int) ceil(2*alpha*boxVectors[2][2]/(3*pow(tol, 0.2)));
     xsize = max(xsize, 5);
     ysize = max(ysize, 5);
     zsize = max(zsize, 5);

platforms/cuda/tests/TestCudaEwald.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008-2009 Stanford University and the Authors.      *
+ * Portions copyright (c) 2008-2010 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -245,7 +245,7 @@ void testErrorTolerance(NonbondedForce::NonbondedMethod method) {
                     diff += delta.dot(delta);
                 }
                 diff = sqrt(diff)/norm;
-                ASSERT(diff < 5*tol);
+                ASSERT(diff < 2*tol);
             }
         }
     }

platforms/opencl/tests/TestOpenCLEwald.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008-2009 Stanford University and the Authors.      *
+ * Portions copyright (c) 2008-2010 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -244,7 +244,7 @@ void testErrorTolerance(NonbondedForce::NonbondedMethod method) {
                     diff += delta.dot(delta);
                 }
                 diff = sqrt(diff)/norm;
-                ASSERT(diff < 5*tol);
+                ASSERT(diff < 2*tol);
             }
         }
     }

platforms/reference/tests/TestReferenceEwald.cpp

@@ -6,7 +6,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2008-2009 Stanford University and the Authors.      *
+ * Portions copyright (c) 2008-2010 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -348,7 +348,7 @@ void testErrorTolerance(NonbondedForce::NonbondedMethod method) {
                     diff += delta.dot(delta);
                 }
                 diff = sqrt(diff)/norm;
-                ASSERT(diff < 5*tol);
+                ASSERT(diff < 2*tol);
             }
         }
     }