content: /*
   * Tencent is pleased to support the open source community by making Angel available.
   *
   * Copyright (C) 2017-2018 THL A29 Limited, a Tencent company. All rights reserved.
   *
   * 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
   *
   * https://opensource.org/licenses/Apache-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 com.tencent.angel.sona.tree.gbdt.histogram;
  
  import com.tencent.angel.sona.tree.gbdt.tree.GBDTParam;
  
  import java.io.Serializable;
  
  public class BinaryGradPair implements GradPair, Serializable {
      private double grad;
      private double hess;
  
      public BinaryGradPair() {}
  
      public BinaryGradPair(double grad, double hess) {
          this.grad = grad;
          this.hess = hess;
      }
  
      @Override
      public void plusBy(GradPair gradPair) {
          this.grad += ((BinaryGradPair) gradPair).grad;
          this.hess += ((BinaryGradPair) gradPair).hess;
      }
  
      public void plusBy(double grad, double hess) {
          this.grad += grad;
          this.hess += hess;
      }
  
      @Override
      public void subtractBy(GradPair gradPair) {
          this.grad -= ((BinaryGradPair) gradPair).grad;
          this.hess -= ((BinaryGradPair) gradPair).hess;
      }
  
      public void subtractBy(double grad, double hess) {
          this.grad -= grad;
          this.hess -= hess;
      }
  
      @Override
      public GradPair plus(GradPair gradPair) {
          GradPair res = this.copy();
          res.plusBy(gradPair);
          return res;
      }
  
      public GradPair plus(double grad, double hess) {
          return new BinaryGradPair(this.grad + grad, this.hess + hess);
      }
  
      @Override
      public GradPair subtract(GradPair gradPair) {
          GradPair res = this.copy();
          res.subtractBy(gradPair);
          return res;
      }
  
      public GradPair subtract(double grad, double hess) {
          return new BinaryGradPair(this.grad - grad, this.hess - hess);
      }
  
      @Override
      public void timesBy(double x) {
          this.grad *= x;
          this.hess *= x;
      }
  
      @Override
      public boolean satisfyWeight(GBDTParam param) {
          return param.satisfyWeight(hess);
      }
  
      @Override
      public float calcGain(GBDTParam param) {
          return (float) param.calcGain(grad, hess);
      }
  
      @Override
      public float calcWeight(GBDTParam param) {
          return (float) param.calcWeight(grad, hess);
      }
  
      @Override
      public float[] calcWeights(GBDTParam param) {
          throw new RuntimeException(String.format("%s does not support multi-class task",
                  this.getClass().getSimpleName()));
      }
  
      @Override
      public BinaryGradPair copy() {
          return new BinaryGradPair(grad, hess);
      }
  
      @Override
      public void clear() {
          this.grad = 0.0;
          this.hess = 0.0;
      }
  
      public double getGrad() {
          return grad;
      }
  
      public double getHess() {
          return hess;
      }
  
      public void setGrad(double grad) {
          this.grad = grad;
      }
  
      public void setHess(double hess) {
          this.hess = hess;
      }
  
      public void set(double grad, double hess) {
          this.grad = grad;
          this.hess = hess;
      }
  
      @Override
      public String toString() {
          return "(" + grad + ", " + hess + ")";
      }
  }
  