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 com.tencent.angel.sona.tree.util.MathUtil;
  
  import java.io.Serializable;
  import java.util.Arrays;
  
  public class MultiGradPair implements GradPair, Serializable {
      private double[] grad;
      private double[] hess;
  
      public MultiGradPair(int numClass, boolean fullHessian) {
          this.grad = new double[numClass];
          if (fullHessian)
              this.hess = new double[(numClass * (numClass + 1)) >> 1];
          else
              this.hess = new double[numClass];
      }
  
      public MultiGradPair(double[] grad, double[] hess) {
          this.grad = grad;
          this.hess = hess;
      }
  
      @Override
      public void plusBy(GradPair gradPair) {
          double[] grad = ((MultiGradPair) gradPair).grad;
          double[] hess = ((MultiGradPair) gradPair).hess;
          for (int i = 0; i < this.grad.length; i++)
              this.grad[i] += grad[i];
          for (int i = 0; i < this.hess.length; i++)
              this.hess[i] += hess[i];
      }
  
      public void plusBy(double[] grad, double[] hess) {
          for (int i = 0; i < this.grad.length; i++)
              this.grad[i] += grad[i];
          for (int i = 0; i < this.hess.length; i++)
              this.hess[i] += hess[i];
      }
  
      @Override
      public void subtractBy(GradPair gradPair) {
          double[] grad = ((MultiGradPair) gradPair).grad;
          double[] hess = ((MultiGradPair) gradPair).hess;
          for (int i = 0; i < this.grad.length; i++)
              this.grad[i] -= grad[i];
          for (int i = 0; i < this.hess.length; i++)
              this.hess[i] -= hess[i];
      }
  
      public void subtractBy(double[] grad, double[] hess) {
          for (int i = 0; i < this.grad.length; i++)
              this.grad[i] -= grad[i];
          for (int i = 0; i < this.hess.length; i++)
              this.hess[i] -= hess[i];
      }
  
      @Override
      public GradPair plus(GradPair gradPair) {
          GradPair res = this.copy();
          res.plusBy(gradPair);
          return res;
      }
  
      public GradPair plus(double[] grad, double[] hess) {
          MultiGradPair res = this.copy();
          res.plusBy(grad, hess);
          return res;
      }
  
      @Override
      public GradPair subtract(GradPair gradPair) {
          GradPair res = this.copy();
          res.subtractBy(gradPair);
          return res;
      }
  
      public GradPair subtract(double[] grad, double[] hess) {
          MultiGradPair res = this.copy();
          res.subtractBy(grad, hess);
          return res;
      }
  
      @Override
      public void timesBy(double x) {
          for (int i = 0; i < this.grad.length; i++)
              this.grad[i] *= x;
          for (int i = 0; i < this.hess.length; i++)
              this.hess[i] *= 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) {
          throw new RuntimeException(String.format("%s does not support binary-class task",
                  this.getClass().getSimpleName()));
      }
  
      @Override
      public float[] calcWeights(GBDTParam param) {
          return MathUtil.doubleArrayToFloatArray(param.calcWeights(grad, hess));
      }
  
      @Override
      public MultiGradPair copy() {
          return new MultiGradPair(grad.clone(), hess.clone());
      }
  
      @Override
      public void clear() {
          Arrays.fill(this.grad, 0.0);
          Arrays.fill(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;
      }
  
      public void set(double[] grad, double[] hess, int offset) {
          // numClass is usually small, so we do not use arraycopy here
          for (int i = 0; i < this.grad.length; i++) {
              this.grad[i] = grad[i + offset];
              this.hess[i] = hess[i + offset];
          }
      }
  
      public void set(double[] grad, int gradOffset, double[] hess, int hessOffset) {
          // numClass is usually small, so we do not use arraycopy here
          for (int i = 0; i < this.grad.length; i++)
              this.grad[i] = grad[i + gradOffset];
          for (int i = 0; i < this.hess.length; i++)
              this.hess[i] = hess[i + hessOffset];
      }
  
      @Override
      public String toString() {
          String gradStr = Arrays.toString(grad);
          if (grad.length == hess.length) {
              return "(" + gradStr + ", diag{" + Arrays.toString(hess) + "})";
          } else {
              int rowSize = 1, offset = 0;
              StringBuilder hessSB = new StringBuilder("[");
              while (rowSize <= grad.length) {
                  hessSB.append("[");
                  hessSB.append(hess[offset]);
                  for (int i = 1; i < rowSize; i++) {
                      hessSB.append(", ");
                      hessSB.append(hess[offset + i]);
                  }
                  hessSB.append("]");
                  offset += rowSize;
                  rowSize++;
              }
              hessSB.append("]");
              return "(" + gradStr + ", " + hessSB.toString() + ")";
          }
      }
  }
  