Merge pull request #2290 from peastman/atan2

Support atan2() in custom expressions

platforms/opencl/src/OpenCLExpressionUtilities.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) 2009-2018 Stanford University and the Authors.      *
+ * Portions copyright (c) 2009-2019 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -464,6 +464,9 @@ void OpenCLExpressionUtilities::processExpression(stringstream& out, const Expre
         case Operation::ATAN:
             out << "atan(" << getTempName(node.getChildren()[0], temps) << ")";
             break;
+        case Operation::ATAN2:
+            out << "atan2(" << getTempName(node.getChildren()[0], temps) << ", " << getTempName(node.getChildren()[1], temps) << ")";
+            break;
         case Operation::SINH:
             out << "sinh(" << getTempName(node.getChildren()[0], temps) << ")";
             break;

tests/TestCustomExternalForce.h

@@ -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) 2008-2015 Stanford University and the Authors.      *
+ * Portions copyright (c) 2008-2019 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -216,6 +216,21 @@ void testIllegalVariable() {
     ASSERT(threwException);
 }
 
+void testAtan2() {
+    System system;
+    system.addParticle(1.0);
+    CustomExternalForce* force = new CustomExternalForce("atan2(x, y)");
+    force->addParticle(0);
+    system.addForce(force);
+    VerletIntegrator integrator(0.01);
+    Context context(system, integrator, platform);
+    vector<Vec3> positions(1);
+    positions[0] = Vec3(1.5, -2.1, 1.2);
+    context.setPositions(positions);
+    State state = context.getState(State::Energy);
+    ASSERT_EQUAL_TOL(atan2(positions[0][0], positions[0][1]), state.getPotentialEnergy(), 1e-5);
+}
+
 void runPlatformTests();
 
 int main(int argc, char* argv[]) {
@@ -226,6 +241,7 @@ int main(int argc, char* argv[]) {
         testPeriodic();
         testZeroPeriodicDistance();
         testIllegalVariable();
+        testAtan2();
         runPlatformTests();
     }
     catch(const exception& e) {

tests/TestParser.cpp

@@ -265,6 +265,7 @@ int main() {
         verifyEvaluation("ceil(x)", -2.1, 3.0, -2.0);
         verifyEvaluation("select(x, 1.0, y)", 0.3, 2.0, 1.0);
         verifyEvaluation("select(x, 1.0, y)", 0.0, 2.0, 2.0);
+        verifyEvaluation("atan2(x, y)", 3.0, 1.5, std::atan(2.0));
         verifyInvalidExpression("1..2");
         verifyInvalidExpression("1*(2+3");
         verifyInvalidExpression("5++4");
@@ -285,6 +286,7 @@ int main() {
         verifyDerivative("asin(x)", "1/sqrt(1-x^2)");
         verifyDerivative("acos(x)", "-1/sqrt(1-x^2)");
         verifyDerivative("atan(x)", "1/(1+x^2)");
+        verifyDerivative("atan2(2*x,y)", "2*y/(4*x^2+y^2)");
         verifyDerivative("sinh(x)", "cosh(x)");
         verifyDerivative("cosh(x)", "sinh(x)");
         verifyDerivative("tanh(x)", "1/(cosh(x)^2)");