001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.math.linear;
018    
019    import org.apache.commons.math.Field;
020    import org.apache.commons.math.FieldElement;
021    import org.apache.commons.math.util.OpenIntToFieldHashMap;
022    
023    /**
024     * Sparse matrix implementation based on an open addressed map.
025     * 
026     * @param <T> the type of the field elements
027     * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $
028     * @since 2.0
029     */
030    public class SparseFieldMatrix<T extends FieldElement<T>> extends AbstractFieldMatrix<T> {
031        /**
032         *  Serial id
033         */
034        private static final long serialVersionUID = 9078068119297757342L;
035        /** Storage for (sparse) matrix elements. */
036        private final OpenIntToFieldHashMap<T> entries;
037        /**
038         * row dimension
039         */
040        private final int rowDimension;
041        /**
042         * column dimension
043         */
044        private final int columnDimension;
045        
046    
047        /**
048         * Creates a matrix with no data.
049         * @param field field to which the elements belong
050         */
051        public SparseFieldMatrix(final Field<T> field) {
052            super(field);
053            rowDimension = 0;
054            columnDimension= 0;
055            entries = new OpenIntToFieldHashMap<T>(field);
056        }
057    
058        /**
059         * Create a new SparseFieldMatrix<T> with the supplied row and column dimensions.
060         *
061         * @param field field to which the elements belong
062         * @param rowDimension  the number of rows in the new matrix
063         * @param columnDimension  the number of columns in the new matrix
064         * @throws IllegalArgumentException if row or column dimension is not positive
065         */
066        public SparseFieldMatrix(final Field<T> field,
067                                 final int rowDimension, final int columnDimension)
068            throws IllegalArgumentException {
069            super(field, rowDimension, columnDimension);
070            this.rowDimension = rowDimension;
071            this.columnDimension = columnDimension;
072            entries = new OpenIntToFieldHashMap<T>(field);
073        }
074        
075        /**
076         * Copy constructor.
077         * @param other The instance to copy
078         */
079        public SparseFieldMatrix(SparseFieldMatrix<T> other) {
080            super(other.getField(), other.getRowDimension(), other.getColumnDimension());
081            rowDimension = other.getRowDimension();
082            columnDimension = other.getColumnDimension();
083            entries = new OpenIntToFieldHashMap<T>(other.entries);
084        }
085    
086        /**
087         * Generic copy constructor.
088         * @param other The instance to copy
089         */
090        public SparseFieldMatrix(FieldMatrix<T> other){
091            super(other.getField(), other.getRowDimension(), other.getColumnDimension());
092            rowDimension = other.getRowDimension();
093            columnDimension = other.getColumnDimension();
094            entries = new OpenIntToFieldHashMap<T>(getField());
095            for (int i = 0; i < rowDimension; i++) {
096                for (int j = 0; j < columnDimension; j++) {
097                    setEntry(i, j, other.getEntry(i, j));
098                }
099            }
100        }
101    
102        /** {@inheritDoc} */
103        @Override
104        public void addToEntry(int row, int column, T increment)
105                throws MatrixIndexException {
106            checkRowIndex(row);
107            checkColumnIndex(column);
108            final int key = computeKey(row, column);
109            final T value = entries.get(key).add(increment);
110            if (getField().getZero().equals(value)) {
111                entries.remove(key);
112            } else {
113                entries.put(key, value);
114            }
115           
116        }
117    
118        /** {@inheritDoc} */
119        @Override
120        public FieldMatrix<T> copy() {
121            return new SparseFieldMatrix<T>(this);
122        }
123    
124        /** {@inheritDoc} */
125        @Override
126        public FieldMatrix<T> createMatrix(int rowDimension, int columnDimension)
127                throws IllegalArgumentException {
128            return new SparseFieldMatrix<T>(getField(), rowDimension, columnDimension);
129        }
130    
131        /** {@inheritDoc} */
132        @Override
133        public int getColumnDimension() {
134            return columnDimension;
135        }
136    
137        /** {@inheritDoc} */
138        @Override
139        public T getEntry(int row, int column) throws MatrixIndexException {
140            checkRowIndex(row);
141            checkColumnIndex(column);
142            return entries.get(computeKey(row, column));
143        }
144    
145        /** {@inheritDoc} */
146        @Override
147        public int getRowDimension() {
148            return rowDimension;
149        }
150    
151        /** {@inheritDoc} */
152        @Override
153        public void multiplyEntry(int row, int column, T factor)
154                throws MatrixIndexException {
155            checkRowIndex(row);
156            checkColumnIndex(column);
157            final int key = computeKey(row, column);
158            final T value = entries.get(key).multiply(factor);
159            if (getField().getZero().equals(value)) {
160                entries.remove(key);
161            } else {
162                entries.put(key, value);
163            }
164            
165        }
166    
167        /** {@inheritDoc} */
168        @Override
169        public void setEntry(int row, int column, T value)
170                throws MatrixIndexException {
171            checkRowIndex(row);
172            checkColumnIndex(column);
173            if (getField().getZero().equals(value)) {
174                entries.remove(computeKey(row, column));
175            } else {
176                entries.put(computeKey(row, column), value);
177            }
178            
179        }
180        /**
181         * Compute the key to access a matrix element
182         * @param row row index of the matrix element
183         * @param column column index of the matrix element
184         * @return key within the map to access the matrix element
185         */
186        private int computeKey(int row, int column) {
187            return row * columnDimension + column;
188        }
189    
190    }