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.graph.client.sampleneighbor2;
  
  import com.tencent.angel.ml.matrix.psf.get.base.GetFunc;
  import com.tencent.angel.ml.matrix.psf.get.base.GetResult;
  import com.tencent.angel.ml.matrix.psf.get.base.PartitionGetParam;
  import com.tencent.angel.ml.matrix.psf.get.base.PartitionGetResult;
  import com.tencent.angel.ps.storage.matrix.ServerMatrix;
  import com.tencent.angel.ps.storage.partition.RowBasedPartition;
  import com.tencent.angel.ps.storage.partition.ServerPartition;
  import com.tencent.angel.ps.storage.vector.ServerLongAnyRow;
  import com.tencent.angel.ps.storage.vector.element.LongArrayElement;
  import it.unimi.dsi.fastutil.ints.Int2ObjectArrayMap;
  import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
  import java.util.List;
  import java.util.Random;
  
  /**
   * Sample the neighbor
   */
  public class SampleNeighbor extends GetFunc {
  
    public SampleNeighbor(SampleNeighborParam param) {
      super(param);
    }
  
    public SampleNeighbor() {
      this(null);
    }
  
    @Override
    public PartitionGetResult partitionGet(PartitionGetParam partParam) {
      PartSampleNeighborParam param = (PartSampleNeighborParam) partParam;
      ServerMatrix matrix = psContext.getMatrixStorageManager().getMatrix(partParam.getMatrixId());
      ServerPartition part = matrix.getPartition(partParam.getPartKey().getPartitionId());
      ServerLongAnyRow row = (ServerLongAnyRow) (((RowBasedPartition) part).getRow(0));
      long[] nodeIds = param.getNodeIds();
      long[][] neighbors = new long[nodeIds.length][];
  
      int count = param.getCount();
      Random r = new Random();
  
      for (int i = 0; i < nodeIds.length; i++) {
        long nodeId = nodeIds[i];
  
        // Get node neighbor number
        LongArrayElement element = (LongArrayElement) (row.get(nodeId));
        if (element == null) {
          neighbors[i] = null;
        } else {
          long[] nodeNeighbors = element.getData();
          if (nodeNeighbors == null || nodeNeighbors.length == 0) {
            neighbors[i] = null;
          } else if (count <= 0 || nodeNeighbors.length <= count) {
            neighbors[i] = nodeNeighbors;
          } else {
            neighbors[i] = new long[count];
            // If the neighbor number > count, just copy a range of neighbors to the result array, the copy position is random
            int startPos = Math.abs(r.nextInt()) % nodeNeighbors.length;
            if (startPos + count <= nodeNeighbors.length) {
              System.arraycopy(nodeNeighbors, startPos, neighbors[i], 0, count);
            } else {
              System
                  .arraycopy(nodeNeighbors, startPos, neighbors[i], 0,
                      nodeNeighbors.length - startPos);
              System.arraycopy(nodeNeighbors, 0, neighbors[i],
                  nodeNeighbors.length - startPos, count - (nodeNeighbors.length - startPos));
            }
          }
        }
      }
  
      return new PartSampleNeighborResult(part.getPartitionKey().getPartitionId(), neighbors);
    }
  
    @Override
    public GetResult merge(List<PartitionGetResult> partResults) {
      Int2ObjectArrayMap<PartitionGetResult> partIdToResultMap = new Int2ObjectArrayMap<>(
          partResults.size());
      for (PartitionGetResult result : partResults) {
        partIdToResultMap.put(((PartSampleNeighborResult) result).getPartId(), result);
      }
  
      SampleNeighborParam param = (SampleNeighborParam) getParam();
      long[] nodeIds = param.getNodeIds();
      List<PartitionGetParam> partParams = param.getPartParams();
  
      Long2ObjectOpenHashMap<long[]> nodeIdToNeighbors = new Long2ObjectOpenHashMap<>(nodeIds.length);
  
      for (PartitionGetParam partParam : partParams) {
        int start = ((PartSampleNeighborParam) partParam).getStartIndex();
        int end = ((PartSampleNeighborParam) partParam).getEndIndex();
        PartSampleNeighborResult partResult = (PartSampleNeighborResult) (partIdToResultMap
            .get(partParam.getPartKey().getPartitionId()));
        long[][] results = partResult.getNodeIdToNeighbors();
        for (int i = start; i < end; i++) {
          nodeIdToNeighbors.put(nodeIds[i], results[i - start]);
        }
      }
  
      return new SampleNeighborResult(nodeIdToNeighbors);
    }
  }
  