CommonRegion.java

/*
 * Copyright 2015 S. Webber
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.oakgp.evolve.crossover;

import static org.oakgp.node.NodeType.areFunctions;
import static org.oakgp.node.NodeType.areTerminals;

import org.oakgp.Arguments;
import org.oakgp.node.FunctionNode;
import org.oakgp.node.Node;

final class CommonRegion {
   /** Private constructor as all methods are static. */
   private CommonRegion() {
      // do nothing
   }

   static Node crossoverAt(Node n1, Node n2, int crossOverPoint) {
      if (areFunctions(n1, n2)) {
         FunctionNode f1 = (FunctionNode) n1;
         FunctionNode f2 = (FunctionNode) n2;
         Arguments arguments = f1.getArguments();
         int argCount = arguments.getArgCount();
         if (argCount == f2.getArguments().getArgCount()) {
            int total = 0;
            for (int i = 0; i < argCount; i++) {
               Node a1 = arguments.getArg(i);
               Node a2 = f2.getArguments().getArg(i);
               int c = getNodeCount(a1, a2);
               if (total + c > crossOverPoint) {
                  return new FunctionNode(f1.getFunction(), arguments.replaceAt(i, crossoverAt(a1, a2, crossOverPoint - total)));
               } else {
                  total += c;
               }
            }
         }
      }

      return sameType(n1, n2) ? n2 : n1;
   }

   static int getNodeCount(Node n1, Node n2) {
      if (areFunctions(n1, n2)) {
         int total = sameType(n1, n2) ? 1 : 0;
         FunctionNode f1 = (FunctionNode) n1;
         FunctionNode f2 = (FunctionNode) n2;
         int argCount = f1.getArguments().getArgCount();
         if (argCount == f2.getArguments().getArgCount()) {
            for (int i = 0; i < argCount; i++) {
               total += getNodeCount(f1.getArguments().getArg(i), f2.getArguments().getArg(i));
            }
         }
         return total;
      } else if (areTerminals(n1, n2)) {
         return sameType(n1, n2) ? 1 : 0;
      } else {
         // terminal node does not match with a function node
         return 0;
      }
   }

   private static boolean sameType(Node n1, Node n2) {
      return n1.getType() == n2.getType();
   }
}