001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.nabla.forward.arithmetic;
018    
019    import org.apache.commons.nabla.DifferentiationException;
020    import org.apache.commons.nabla.forward.analysis.InstructionsTransformer;
021    import org.apache.commons.nabla.forward.analysis.MethodDifferentiator;
022    import org.objectweb.asm.Opcodes;
023    import org.objectweb.asm.Type;
024    import org.objectweb.asm.tree.AbstractInsnNode;
025    import org.objectweb.asm.tree.InsnList;
026    import org.objectweb.asm.tree.InsnNode;
027    import org.objectweb.asm.tree.MethodInsnNode;
028    
029    /** Differentiation transformer for DSUB instructions.
030     * @version $Id$
031     */
032    public class DSubTransformer implements InstructionsTransformer {
033    
034        /** Name of the {@link org.apache.commons.math3.analysis.differentiation.DerivativeStructure} method corresponding to the subtraction. */
035        private static final String SUBTRACT_METHOD = "subtract";
036    
037        /** Name of the {@link org.apache.commons.math3.analysis.differentiation.DerivativeStructure} method corresponding to the negation. */
038        private static final String NEGATE_METHOD = "negate";
039    
040        /** Indicator for top stack element conversion. */
041        private final boolean stack0Converted;
042    
043        /** Indicator for next to top stack element conversion. */
044        private final boolean stack1Converted;
045    
046        /** Simple constructor.
047         * @param stack0Converted if true, the top level stack element has already been converted
048         * @param stack1Converted if true, the next to top level stack element has already been converted
049         */
050        public DSubTransformer(final boolean stack0Converted, final boolean stack1Converted) {
051            this.stack0Converted = stack0Converted;
052            this.stack1Converted = stack1Converted;
053        }
054    
055        /** {@inheritDoc} */
056        public InsnList getReplacement(final AbstractInsnNode insn,
057                                       final MethodDifferentiator methodDifferentiator)
058            throws DifferentiationException {
059    
060            final InsnList list = new InsnList();
061    
062            if (stack1Converted) {
063                if (stack0Converted) {
064                    list.add(new MethodInsnNode(Opcodes.INVOKEVIRTUAL, DS_TYPE.getInternalName(),
065                                                SUBTRACT_METHOD,
066                                                Type.getMethodDescriptor(DS_TYPE, DS_TYPE)));
067                } else {
068                    list.add(new MethodInsnNode(Opcodes.INVOKEVIRTUAL, DS_TYPE.getInternalName(),
069                                                SUBTRACT_METHOD,
070                                                Type.getMethodDescriptor(DS_TYPE, Type.DOUBLE_TYPE)));
071                }
072            } else {
073                list.add(new InsnNode(Opcodes.DUP_X2));
074                list.add(new InsnNode(Opcodes.POP));
075                list.add(new MethodInsnNode(Opcodes.INVOKEVIRTUAL, DS_TYPE.getInternalName(),
076                                            SUBTRACT_METHOD,
077                                            Type.getMethodDescriptor(DS_TYPE, Type.DOUBLE_TYPE)));
078                list.add(new MethodInsnNode(Opcodes.INVOKEVIRTUAL, DS_TYPE.getInternalName(),
079                                            NEGATE_METHOD,
080                                            Type.getMethodDescriptor(DS_TYPE)));
081            }
082    
083            return list;
084    
085        }
086    
087    }