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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.giraph.aggregators.matrix.sparse;
20  
21  import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
22  
23  /**
24   * A double matrix holds the values of the entries in double vectors. It keeps
25   * one double aggregator per matrix row.
26   */
27  public class DoubleSparseMatrix {
28    /** The number of rows in the matrix */
29    private int numRows;
30    /** The rows of the matrix */
31    private Int2ObjectOpenHashMap<DoubleSparseVector> rows;
32  
33    /**
34     * Create a new matrix with the given number of rows.
35     *
36     * @param numRows the number of rows.
37     */
38    public DoubleSparseMatrix(int numRows) {
39      this.numRows = numRows;
40      rows = new Int2ObjectOpenHashMap<DoubleSparseVector>(numRows);
41      rows.defaultReturnValue(null);
42    }
43  
44    /**
45     * Create a empty matrix with all values set to 0.0
46     */
47    public void initialize() {
48      rows.clear();
49      for (int i = 0; i < numRows; ++i) {
50        setRow(i, new DoubleSparseVector());
51      }
52    }
53  
54    /**
55     * Get the number of rows in the matrix.
56     *
57     * @return the number of rows.
58     */
59    public int getNumRows() {
60      return numRows;
61    }
62  
63    /**
64     * Get a specific entry of the matrix.
65     *
66     * @param i the row
67     * @param j the column
68     * @return the value of the entry
69     */
70    public double get(int i, int j) {
71      return rows.get(i).get(j);
72    }
73  
74    /**
75     * Set a specific entry of the matrix.
76     *
77     * @param i the row
78     * @param j the column
79     * @param v the value of the entry
80     */
81    public void set(int i, int j, double v) {
82      rows.get(i).set(j, v);
83    }
84  
85    /**
86     * Get a specific row of the matrix.
87     *
88     * @param i the row number
89     * @return the row of the matrix
90     */
91    DoubleSparseVector getRow(int i) {
92      return rows.get(i);
93    }
94  
95    /**
96     * Set the double vector as the row specified.
97     *
98     * @param i the row
99     * @param vec the vector to set as the row
100    */
101   void setRow(int i, DoubleSparseVector vec) {
102     rows.put(i, vec);
103   }
104 }