Optimized processing of expressions with tabulated functions

platforms/reference/include/ReferenceTabulatedFunction.h

@@ -9,7 +9,7 @@
  * Biological Structures at Stanford, funded under the NIH Roadmap for        *
  * Medical Research, grant U54 GM072970. See https://simtk.org.               *
  *                                                                            *
- * Portions copyright (c) 2014-2016 Stanford University and the Authors.      *
+ * Portions copyright (c) 2014-2019 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -35,6 +35,7 @@
 #include "openmm/TabulatedFunction.h"
 #include "openmm/internal/windowsExport.h"
 #include "lepton/CustomFunction.h"
+#include <memory>
 #include <vector>
 
 namespace OpenMM {
@@ -146,6 +147,22 @@ private:
     std::vector<double> values;
 };
 
+/**
+ * This is a lightweight wrapper around an immutable CustomFunction.  It makes
+ * cloning very inexpensive since nothing needs to be copied except a single
+ * pointer.
+ */
+class OPENMM_EXPORT SharedFunctionWrapper : public Lepton::CustomFunction {
+public:
+    SharedFunctionWrapper(std::shared_ptr<const CustomFunction> pointer);
+    int getNumArguments() const;
+    double evaluate(const double* arguments) const;
+    double evaluateDerivative(const double* arguments, const int* derivOrder) const;
+    CustomFunction* clone() const;
+private:
+    std::shared_ptr<const CustomFunction> pointer;
+};
+
 } // namespace OpenMM
 
 #endif /*OPENMM_REFERENCETABULATEDFUNCTION_H_*/

platforms/reference/src/ReferenceTabulatedFunction.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) 2014-2016 Stanford University and the Authors.      *
+ * Portions copyright (c) 2014-2019 Stanford University and the Authors.      *
  * Authors: Peter Eastman                                                     *
  * Contributors:                                                              *
  *                                                                            *
@@ -56,19 +56,22 @@ using namespace std;
 using Lepton::CustomFunction;
 
 extern "C" OPENMM_EXPORT CustomFunction* createReferenceTabulatedFunction(const TabulatedFunction& function) {
+    CustomFunction* fn;
     if (dynamic_cast<const Continuous1DFunction*>(&function) != NULL)
-        return new ReferenceContinuous1DFunction(dynamic_cast<const Continuous1DFunction&>(function));
-    if (dynamic_cast<const Continuous2DFunction*>(&function) != NULL)
-        return new ReferenceContinuous2DFunction(dynamic_cast<const Continuous2DFunction&>(function));
-    if (dynamic_cast<const Continuous3DFunction*>(&function) != NULL)
-        return new ReferenceContinuous3DFunction(dynamic_cast<const Continuous3DFunction&>(function));
-    if (dynamic_cast<const Discrete1DFunction*>(&function) != NULL)
-        return new ReferenceDiscrete1DFunction(dynamic_cast<const Discrete1DFunction&>(function));
-    if (dynamic_cast<const Discrete2DFunction*>(&function) != NULL)
-        return new ReferenceDiscrete2DFunction(dynamic_cast<const Discrete2DFunction&>(function));
-    if (dynamic_cast<const Discrete3DFunction*>(&function) != NULL)
-        return new ReferenceDiscrete3DFunction(dynamic_cast<const Discrete3DFunction&>(function));
+        fn = new ReferenceContinuous1DFunction(dynamic_cast<const Continuous1DFunction&>(function));
+    else if (dynamic_cast<const Continuous2DFunction*>(&function) != NULL)
+        fn = new ReferenceContinuous2DFunction(dynamic_cast<const Continuous2DFunction&>(function));
+    else if (dynamic_cast<const Continuous3DFunction*>(&function) != NULL)
+        fn = new ReferenceContinuous3DFunction(dynamic_cast<const Continuous3DFunction&>(function));
+    else if (dynamic_cast<const Discrete1DFunction*>(&function) != NULL)
+        fn = new ReferenceDiscrete1DFunction(dynamic_cast<const Discrete1DFunction&>(function));
+    else if (dynamic_cast<const Discrete2DFunction*>(&function) != NULL)
+        fn = new ReferenceDiscrete2DFunction(dynamic_cast<const Discrete2DFunction&>(function));
+    else if (dynamic_cast<const Discrete3DFunction*>(&function) != NULL)
+        fn = new ReferenceDiscrete3DFunction(dynamic_cast<const Discrete3DFunction&>(function));
+    else
         throw OpenMMException("createReferenceTabulatedFunction: Unknown function type");
+    return new SharedFunctionWrapper(shared_ptr<const CustomFunction>(fn));
 }
 
 ReferenceContinuous1DFunction::ReferenceContinuous1DFunction(const Continuous1DFunction& function) : function(function) {
@@ -298,3 +301,22 @@ double ReferenceDiscrete3DFunction::evaluateDerivative(const double* arguments,
 CustomFunction* ReferenceDiscrete3DFunction::clone() const {
     return new ReferenceDiscrete3DFunction(function);
 }
+
+SharedFunctionWrapper::SharedFunctionWrapper(shared_ptr<const CustomFunction> pointer) : pointer(pointer) {
+}
+
+int SharedFunctionWrapper::getNumArguments() const {
+    return pointer->getNumArguments();
+}
+
+double SharedFunctionWrapper::evaluate(const double* arguments) const {
+    return pointer->evaluate(arguments);
+}
+
+double SharedFunctionWrapper::evaluateDerivative(const double* arguments, const int* derivOrder) const {
+    return pointer->evaluateDerivative(arguments, derivOrder);
+}
+
+CustomFunction* SharedFunctionWrapper::clone() const {
+    return new SharedFunctionWrapper(pointer);
+}