/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 opennlp.maxent.quasinewton;

/**
 * sample function for unit tests of LineSearch
 */
public class QuadraticFunction implements DifferentiableFunction {

  public double valueAt(double[] x) {
  // -(x-2)^2 + 4;
    return (Math.pow(x[0] - 2.0, 2.0) * -1.0) + 4.0;
  }

  public double[] gradientAt(double[] x) {
    return new double[] {(-2.0 * x[0]) + 4.0};
  }

  public int getDomainDimension() {
    return 1;
  }
}
