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Diffstat (limited to 'src/main/java/org/apache/commons/math3/linear/SparseFieldMatrix.java')
| -rw-r--r-- | src/main/java/org/apache/commons/math3/linear/SparseFieldMatrix.java | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/linear/SparseFieldMatrix.java b/src/main/java/org/apache/commons/math3/linear/SparseFieldMatrix.java new file mode 100644 index 0000000..a1df939 --- /dev/null +++ b/src/main/java/org/apache/commons/math3/linear/SparseFieldMatrix.java @@ -0,0 +1,184 @@ +/* + * 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.commons.math3.linear; + +import org.apache.commons.math3.Field; +import org.apache.commons.math3.FieldElement; +import org.apache.commons.math3.util.OpenIntToFieldHashMap; + +/** + * Sparse matrix implementation based on an open addressed map. + * + * <p>Caveat: This implementation assumes that, for any {@code x}, the equality {@code x * 0d == 0d} + * holds. But it is is not true for {@code NaN}. Moreover, zero entries will lose their sign. Some + * operations (that involve {@code NaN} and/or infinities) may thus give incorrect results. + * + * @param <T> the type of the field elements + * @since 2.0 + */ +public class SparseFieldMatrix<T extends FieldElement<T>> extends AbstractFieldMatrix<T> { + + /** Storage for (sparse) matrix elements. */ + private final OpenIntToFieldHashMap<T> entries; + + /** Row dimension. */ + private final int rows; + + /** Column dimension. */ + private final int columns; + + /** + * Create a matrix with no data. + * + * @param field Field to which the elements belong. + */ + public SparseFieldMatrix(final Field<T> field) { + super(field); + rows = 0; + columns = 0; + entries = new OpenIntToFieldHashMap<T>(field); + } + + /** + * Create a new SparseFieldMatrix<T> with the supplied row and column dimensions. + * + * @param field Field to which the elements belong. + * @param rowDimension Number of rows in the new matrix. + * @param columnDimension Number of columns in the new matrix. + * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException if row or column + * dimension is not positive. + */ + public SparseFieldMatrix( + final Field<T> field, final int rowDimension, final int columnDimension) { + super(field, rowDimension, columnDimension); + this.rows = rowDimension; + this.columns = columnDimension; + entries = new OpenIntToFieldHashMap<T>(field); + } + + /** + * Copy constructor. + * + * @param other Instance to copy. + */ + public SparseFieldMatrix(SparseFieldMatrix<T> other) { + super(other.getField(), other.getRowDimension(), other.getColumnDimension()); + rows = other.getRowDimension(); + columns = other.getColumnDimension(); + entries = new OpenIntToFieldHashMap<T>(other.entries); + } + + /** + * Generic copy constructor. + * + * @param other Instance to copy. + */ + public SparseFieldMatrix(FieldMatrix<T> other) { + super(other.getField(), other.getRowDimension(), other.getColumnDimension()); + rows = other.getRowDimension(); + columns = other.getColumnDimension(); + entries = new OpenIntToFieldHashMap<T>(getField()); + for (int i = 0; i < rows; i++) { + for (int j = 0; j < columns; j++) { + setEntry(i, j, other.getEntry(i, j)); + } + } + } + + /** {@inheritDoc} */ + @Override + public void addToEntry(int row, int column, T increment) { + checkRowIndex(row); + checkColumnIndex(column); + final int key = computeKey(row, column); + final T value = entries.get(key).add(increment); + if (getField().getZero().equals(value)) { + entries.remove(key); + } else { + entries.put(key, value); + } + } + + /** {@inheritDoc} */ + @Override + public FieldMatrix<T> copy() { + return new SparseFieldMatrix<T>(this); + } + + /** {@inheritDoc} */ + @Override + public FieldMatrix<T> createMatrix(int rowDimension, int columnDimension) { + return new SparseFieldMatrix<T>(getField(), rowDimension, columnDimension); + } + + /** {@inheritDoc} */ + @Override + public int getColumnDimension() { + return columns; + } + + /** {@inheritDoc} */ + @Override + public T getEntry(int row, int column) { + checkRowIndex(row); + checkColumnIndex(column); + return entries.get(computeKey(row, column)); + } + + /** {@inheritDoc} */ + @Override + public int getRowDimension() { + return rows; + } + + /** {@inheritDoc} */ + @Override + public void multiplyEntry(int row, int column, T factor) { + checkRowIndex(row); + checkColumnIndex(column); + final int key = computeKey(row, column); + final T value = entries.get(key).multiply(factor); + if (getField().getZero().equals(value)) { + entries.remove(key); + } else { + entries.put(key, value); + } + } + + /** {@inheritDoc} */ + @Override + public void setEntry(int row, int column, T value) { + checkRowIndex(row); + checkColumnIndex(column); + if (getField().getZero().equals(value)) { + entries.remove(computeKey(row, column)); + } else { + entries.put(computeKey(row, column), value); + } + } + + /** + * Compute the key to access a matrix element. + * + * @param row Row index of the matrix element. + * @param column Column index of the matrix element. + * @return the key within the map to access the matrix element. + */ + private int computeKey(int row, int column) { + return row * columns + column; + } +} |