Continuing to implement new CUDA platform: NonbondedForce

platforms/cuda2/tests/TestCudaEwald.cpp

+/* -------------------------------------------------------------------------- *
+ *                                   OpenMM                                   *
+ * -------------------------------------------------------------------------- *
+ * This is part of the OpenMM molecular simulation toolkit originating from   *
+ * Simbios, the NIH National Center for Physics-Based Simulation of           *
+ * Biological Structures at Stanford, funded under the NIH Roadmap for        *
+ * Medical Research, grant U54 GM072970. See https://simtk.org.               *
+ *                                                                            *
+ * Portions copyright (c) 2008-2012 Stanford University and the Authors.      *
+ * Authors: Peter Eastman                                                     *
+ * Contributors:                                                              *
+ *                                                                            *
+ * Permission is hereby granted, free of charge, to any person obtaining a    *
+ * copy of this software and associated documentation files (the "Software"), *
+ * to deal in the Software without restriction, including without limitation  *
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
+ * and/or sell copies of the Software, and to permit persons to whom the      *
+ * Software is furnished to do so, subject to the following conditions:       *
+ *                                                                            *
+ * The above copyright notice and this permission notice shall be included in *
+ * all copies or substantial portions of the Software.                        *
+ *                                                                            *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
+ * THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,    *
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR      *
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE  *
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.                                     *
+ * -------------------------------------------------------------------------- */
+
+/**
+ * This tests the Ewald summation method CUDA implementation of NonbondedForce.
+ */
+
+#include "openmm/internal/AssertionUtilities.h"
+#include "openmm/Context.h"
+#include "CudaPlatform.h"
+#include "ReferencePlatform.h"
+#include "openmm/NonbondedForce.h"
+#include "openmm/System.h"
+#include "openmm/LangevinIntegrator.h"
+#include "openmm/VerletIntegrator.h"
+#include "openmm/internal/ContextImpl.h"
+#include "../src/SimTKUtilities/SimTKOpenMMRealType.h"
+#include "sfmt/SFMT.h"
+#include <iostream>
+#include <vector>
+
+using namespace OpenMM;
+using namespace std;
+
+const double TOL = 1e-5;
+
+void testEwaldPME(bool includeExceptions) {
+
+//      Use amorphous NaCl system for the tests
+
+    const int numParticles 	= 894;
+    const double cutoff 	= 1.2;
+    const double boxSize 	= 3.00646;
+    double tol 				= 1e-5;
+
+    CudaPlatform cu;
+    ReferencePlatform reference;
+    System system;
+    NonbondedForce* nonbonded = new NonbondedForce();
+    nonbonded->setNonbondedMethod(NonbondedForce::Ewald);
+    nonbonded->setCutoffDistance(cutoff);
+    nonbonded->setEwaldErrorTolerance(tol);
+
+    for (int i = 0; i < numParticles/2; i++)
+        system.addParticle(22.99);
+    for (int i = 0; i < numParticles/2; i++)
+        system.addParticle(35.45);
+    for (int i = 0; i < numParticles/2; i++)
+        nonbonded->addParticle(1.0, 1.0,0.0);
+    for (int i = 0; i < numParticles/2; i++)
+        nonbonded->addParticle(-1.0, 1.0,0.0);
+    system.setDefaultPeriodicBoxVectors(Vec3(boxSize, 0, 0), Vec3(0, boxSize, 0), Vec3(0, 0, boxSize));
+    system.addForce(nonbonded);
+
+    vector<Vec3> positions(numParticles);
+    #include "nacl_amorph.dat"
+    if (includeExceptions) {
+        // Add some exclusions.
+
+        for (int i = 0; i < numParticles-1; i++) {
+            Vec3 delta = positions[i]-positions[i+1];
+            if (sqrt(delta.dot(delta)) < 0.5*cutoff)
+                nonbonded->addException(i, i+1, i%2 == 0 ? 0.0 : 0.5, 1.0, 0.0);
+        }
+    }
+
+//    (1)  Check whether the Reference and CUDA platforms agree when using Ewald Method
+
+    VerletIntegrator integrator1(0.01);
+    VerletIntegrator integrator2(0.01);
+    Context cuContext(system, integrator1, cu);
+    Context referenceContext(system, integrator2, reference);
+    cuContext.setPositions(positions);
+    referenceContext.setPositions(positions);
+    State cuState = cuContext.getState(State::Forces | State::Energy);
+    State referenceState = referenceContext.getState(State::Forces | State::Energy);
+    tol = 1e-2;
+    for (int i = 0; i < numParticles; i++) {
+        ASSERT_EQUAL_VEC(referenceState.getForces()[i], cuState.getForces()[i], tol);
+    }
+    tol = 1e-5;
+    ASSERT_EQUAL_TOL(referenceState.getPotentialEnergy(), cuState.getPotentialEnergy(), tol);
+
+//    (2) Check whether Ewald method in CUDA is self-consistent
+
+    double norm = 0.0;
+    for (int i = 0; i < numParticles; ++i) {
+        Vec3 f = cuState.getForces()[i];
+        norm += f[0]*f[0] + f[1]*f[1] + f[2]*f[2];
+    }
+
+    norm = std::sqrt(norm);
+    const double delta = 5e-3;
+    double step = delta/norm;
+    for (int i = 0; i < numParticles; ++i) {
+        Vec3 p = positions[i];
+        Vec3 f = cuState.getForces()[i];
+        positions[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
+    }
+    VerletIntegrator integrator3(0.01);
+    Context cuContext2(system, integrator3, cu);
+    cuContext2.setPositions(positions);
+
+    tol = 1e-2;
+    State cuState2 = cuContext2.getState(State::Energy);
+    ASSERT_EQUAL_TOL(norm, (cuState2.getPotentialEnergy()-cuState.getPotentialEnergy())/delta, tol)
+
+//    (3)  Check whether the Reference and CUDA platforms agree when using PME
+
+    nonbonded->setNonbondedMethod(NonbondedForce::PME);
+    cuContext.reinitialize();
+    referenceContext.reinitialize();
+    cuContext.setPositions(positions);
+    referenceContext.setPositions(positions);
+    cuState = cuContext.getState(State::Forces | State::Energy);
+    referenceState = referenceContext.getState(State::Forces | State::Energy);
+    tol = 1e-2;
+    for (int i = 0; i < numParticles; i++) {
+        ASSERT_EQUAL_VEC(referenceState.getForces()[i], cuState.getForces()[i], tol);
+    }
+    tol = 1e-5;
+    ASSERT_EQUAL_TOL(referenceState.getPotentialEnergy(), cuState.getPotentialEnergy(), tol);
+
+//    (4) Check whether PME method in CUDA is self-consistent
+
+    norm = 0.0;
+    for (int i = 0; i < numParticles; ++i) {
+        Vec3 f = cuState.getForces()[i];
+        norm += f[0]*f[0] + f[1]*f[1] + f[2]*f[2];
+    }
+
+    norm = std::sqrt(norm);
+    step = delta/norm;
+    for (int i = 0; i < numParticles; ++i) {
+        Vec3 p = positions[i];
+        Vec3 f = cuState.getForces()[i];
+        positions[i] = Vec3(p[0]-f[0]*step, p[1]-f[1]*step, p[2]-f[2]*step);
+    }
+    VerletIntegrator integrator4(0.01);
+    Context cuContext3(system, integrator4, cu);
+    cuContext3.setPositions(positions);
+
+    tol = 1e-2;
+    State cuState3 = cuContext3.getState(State::Energy);
+    ASSERT_EQUAL_TOL(norm, (cuState3.getPotentialEnergy()-cuState.getPotentialEnergy())/delta, tol)
+}
+
+void testEwald2Ions() {
+    CudaPlatform platform;
+    System system;
+    system.addParticle(1.0);
+    system.addParticle(1.0);
+    VerletIntegrator integrator(0.01);
+    NonbondedForce* nonbonded = new NonbondedForce();
+    nonbonded->addParticle(1.0, 1, 0);
+    nonbonded->addParticle(-1.0, 1, 0);
+    nonbonded->setNonbondedMethod(NonbondedForce::Ewald);
+    const double cutoff = 2.0;
+    nonbonded->setCutoffDistance(cutoff);
+    nonbonded->setEwaldErrorTolerance(TOL);
+    system.setDefaultPeriodicBoxVectors(Vec3(6, 0, 0), Vec3(0, 6, 0), Vec3(0, 0, 6));
+    system.addForce(nonbonded);
+    Context context(system, integrator, platform);
+    vector<Vec3> positions(2);
+    positions[0] = Vec3(3.048000,2.764000,3.156000);
+    positions[1] = Vec3(2.809000,2.888000,2.571000);
+    context.setPositions(positions);
+    State state = context.getState(State::Forces | State::Energy);
+    const vector<Vec3>& forces = state.getForces();
+
+    ASSERT_EQUAL_VEC(Vec3(-123.711,  64.1877, -302.716), forces[0], 10*TOL);
+    ASSERT_EQUAL_VEC(Vec3( 123.711, -64.1877,  302.716), forces[1], 10*TOL);
+    ASSERT_EQUAL_TOL(-217.276, state.getPotentialEnergy(), 0.01/*10*TOL*/);
+}
+
+void testErrorTolerance(NonbondedForce::NonbondedMethod method) {
+    // Create a cloud of random point charges.
+
+    const int numParticles = 51;
+    const double boxWidth = 5.0;
+    System system;
+    system.setDefaultPeriodicBoxVectors(Vec3(boxWidth, 0, 0), Vec3(0, boxWidth, 0), Vec3(0, 0, boxWidth));
+    NonbondedForce* force = new NonbondedForce();
+    system.addForce(force);
+    vector<Vec3> positions(numParticles);
+    OpenMM_SFMT::SFMT sfmt;
+    init_gen_rand(0, sfmt);
+
+    for (int i = 0; i < numParticles; i++) {
+        system.addParticle(1.0);
+        force->addParticle(-1.0+i*2.0/(numParticles-1), 1.0, 0.0);
+        positions[i] = Vec3(boxWidth*genrand_real2(sfmt), boxWidth*genrand_real2(sfmt), boxWidth*genrand_real2(sfmt));
+    }
+    force->setNonbondedMethod(method);
+    CudaPlatform platform;
+
+    // For various values of the cutoff and error tolerance, see if the actual error is reasonable.
+
+    for (double cutoff = 1.0; cutoff < boxWidth/2; cutoff *= 1.2) {
+        force->setCutoffDistance(cutoff);
+        vector<Vec3> refForces;
+        double norm = 0.0;
+        for (double tol = 5e-5; tol < 1e-3; tol *= 2.0) {
+            force->setEwaldErrorTolerance(tol);
+            VerletIntegrator integrator(0.01);
+            Context context(system, integrator, platform);
+            context.setPositions(positions);
+            State state = context.getState(State::Forces);
+            if (refForces.size() == 0) {
+                refForces = state.getForces();
+                for (int i = 0; i < numParticles; i++)
+                    norm += refForces[i].dot(refForces[i]);
+                norm = sqrt(norm);
+            }
+            else {
+                double diff = 0.0;
+                for (int i = 0; i < numParticles; i++) {
+                    Vec3 delta = refForces[i]-state.getForces()[i];
+                    diff += delta.dot(delta);
+                }
+                diff = sqrt(diff)/norm;
+                ASSERT(diff < 2*tol);
+            }
+        }
+    }
+}
+
+int main() {
+    try {
+     testEwaldPME(false);
+     testEwaldPME(true);
+//     testEwald2Ions();
+     testErrorTolerance(NonbondedForce::Ewald);
+     testErrorTolerance(NonbondedForce::PME);
+    }
+    catch(const exception& e) {
+        cout << "exception: " << e.what() << endl;
+        return 1;
+    }
+    cout << "Done" << endl;
+    return 0;
+}