/*

  * 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 org.apache.giraph.aggregators.matrix.sparse;

 import it.unimi.dsi.fastutil.ints.Int2FloatMap;

 import java.io.DataInput;

 import java.io.DataOutput;

 import java.io.IOException;

 import it.unimi.dsi.fastutil.ints.Int2FloatOpenHashMap;

 import it.unimi.dsi.fastutil.objects.ObjectIterator;

 import org.apache.hadoop.io.Writable;

 /**

  * The float vector holds the values of a particular row.

  */

 public class FloatSparseVector implements Writable {

   /**

    * The entries of the vector are (key, value) pairs of the form (row, value)

    */

   private Int2FloatOpenHashMap entries = null;

   /**

    * Create a new vector with default size.

    */

   public FloatSparseVector() {

     initialize(Int2FloatOpenHashMap.DEFAULT_INITIAL_SIZE);

   }

   /**

    * Create a new vector with given size.

    *

    * @param size the size of the vector

    */

   public FloatSparseVector(int size) {

     initialize(size);

   }

   /**

    * Initialize the values of the vector. The default value is 0.0

    *

    * @param size the size of the vector

    */

   private void initialize(int size) {

     entries = new Int2FloatOpenHashMap(size);

     entries.defaultReturnValue(0.0f);

   }

   /**

    * Get a particular entry of the vector.

    *

    * @param i the entry

    * @return the value of the entry.

    */

   public float get(int i) {

     return entries.get(i);

   }

   /**

    * Set the given value to the entry specified.

    *

    * @param i the entry

    * @param value the value to set to the entry

    */

   public void set(int i, float value) {

     entries.put(i, value);

   }

   /**

    * Clear the contents of the vector.

    */

   public void clear() {

     entries.clear();

   }

   /**

    * Add the vector specified. This is a vector addition that does an

    * element-by-element addition.

    *

    * @param other the vector to add.

    */

   public void add(FloatSparseVector other) {

     ObjectIterator<Int2FloatMap.Entry> iter =

         other.entries.int2FloatEntrySet().fastIterator();

     while (iter.hasNext()) {

       Int2FloatMap.Entry entry = iter.next();

       entries.addTo(entry.getIntKey(), entry.getFloatValue());

     }

   }

   @Override

   public void write(DataOutput out) throws IOException {

     out.writeInt(entries.size());

     ObjectIterator<Int2FloatMap.Entry> iter =

         entries.int2FloatEntrySet().fastIterator();

     while (iter.hasNext()) {

       Int2FloatMap.Entry entry = iter.next();

       out.writeInt(entry.getIntKey());

       out.writeFloat(entry.getFloatValue());

     }

   }

   @Override

   public void readFields(DataInput in) throws IOException {

     int size = in.readInt();

     initialize(size);

     for (int i = 0; i < size; ++i) {

       int row = in.readInt();

       float value = in.readFloat();

       entries.put(row, value);

     }

   }

 }