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.algorithmic.forward.functions;
018    
019    import org.apache.commons.nabla.algorithmic.forward.analysis.MethodDifferentiator;
020    import org.apache.commons.nabla.core.DifferentiationException;
021    import org.objectweb.asm.Opcodes;
022    import org.objectweb.asm.tree.InsnList;
023    import org.objectweb.asm.tree.InsnNode;
024    import org.objectweb.asm.tree.MethodInsnNode;
025    import org.objectweb.asm.tree.VarInsnNode;
026    
027    /** Differentiation transformer for the atan2 function invocation instructions.
028     */
029    public class Atan2Transformer2 implements MathInvocationTransformer {
030    
031        /** {@inheritDoc} */
032        public InsnList getReplacementList(final String owner, final MethodDifferentiator methodDifferentiator)
033            throws DifferentiationException {
034    
035            final int tmp1 = methodDifferentiator.getTmp(1);
036            final int tmp2 = methodDifferentiator.getTmp(2);
037            final int tmp3 = methodDifferentiator.getTmp(3);
038    
039            // generate differential code
040            // ... y, x0, x1  --> ...  atan2(y, x0), -x1*y/(x0^2+y^2)
041            final InsnList list = new InsnList();
042            list.add(new VarInsnNode(Opcodes.DSTORE, tmp3)); // => y, x0
043            list.add(new VarInsnNode(Opcodes.DSTORE, tmp2)); // => y
044            list.add(new VarInsnNode(Opcodes.DSTORE, tmp1)); // =>
045            list.add(new VarInsnNode(Opcodes.DLOAD,  tmp1)); // => y
046            list.add(new VarInsnNode(Opcodes.DLOAD,  tmp2)); // => y, x0
047            list.add(new MethodInsnNode(Opcodes.INVOKESTATIC, owner, "atan2", DD_RETURN_D_DESCRIPTOR)); // => atan2(y,x0)
048            list.add(new VarInsnNode(Opcodes.DLOAD,  tmp3)); // => atan2(y,x0), x1
049            list.add(new VarInsnNode(Opcodes.DLOAD,  tmp1)); // => atan2(y,x0), x1, y
050            list.add(new InsnNode(Opcodes.DMUL));            // => atan2(y,x0), x1*y
051            list.add(new InsnNode(Opcodes.DNEG));            // => atan2(y,x0), -x1*y
052            list.add(new VarInsnNode(Opcodes.DLOAD,  tmp2)); // => atan2(y,x0), -x1*y, x0
053            list.add(new InsnNode(Opcodes.DUP2));            // => atan2(y,x0), -x1*y, x0, x0
054            list.add(new InsnNode(Opcodes.DMUL));            // => atan2(y,x0), -x1*y, x0^2
055            list.add(new VarInsnNode(Opcodes.DLOAD,  tmp1)); // => atan2(y,x0), -x1*y, x0^2, y
056            list.add(new InsnNode(Opcodes.DUP2));            // => atan2(y,x0), -x1*y, x0^2, y, y
057            list.add(new InsnNode(Opcodes.DMUL));            // => atan2(y,x0), -x1*y, x0^2, y^2
058            list.add(new InsnNode(Opcodes.DADD));            // => atan2(y,x0), -x1*y, x0^2+y^2
059            list.add(new InsnNode(Opcodes.DDIV));            // => atan2(y,x0), -x1*y/(x0^2+y^2)
060            return list;
061    
062        }
063    
064    }