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The Apache Commons Math project is a library of lightweight, self-contained mathematics and statistics components addressing the most common practical problems not immediately available in the Java programming language or commons-lang.
/*
* 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.util;
import java.util.NoSuchElementException;
import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.NotStrictlyPositiveException;
import org.apache.commons.math3.exception.OutOfRangeException;
/**
* Converter between unidimensional storage structure and multidimensional
* conceptual structure.
* This utility will convert from indices in a multidimensional structure
* to the corresponding index in a one-dimensional array. For example,
* assuming that the ranges (in 3 dimensions) of indices are 2, 4 and 3,
* the following correspondences, between 3-tuples indices and unidimensional
* indices, will hold:
*
* - (0, 0, 0) corresponds to 0
* - (0, 0, 1) corresponds to 1
* - (0, 0, 2) corresponds to 2
* - (0, 1, 0) corresponds to 3
* - ...
* - (1, 0, 0) corresponds to 12
* - ...
* - (1, 3, 2) corresponds to 23
*
*
* @since 2.2
*/
public class MultidimensionalCounter implements Iterable {
/**
* Number of dimensions.
*/
private final int dimension;
/**
* Offset for each dimension.
*/
private final int[] uniCounterOffset;
/**
* Counter sizes.
*/
private final int[] size;
/**
* Total number of (one-dimensional) slots.
*/
private final int totalSize;
/**
* Index of last dimension.
*/
private final int last;
/**
* Perform iteration over the multidimensional counter.
*/
public class Iterator implements java.util.Iterator {
/**
* Multidimensional counter.
*/
private final int[] counter = new int[dimension];
/**
* Unidimensional counter.
*/
private int count = -1;
/**
* Maximum value for {@link #count}.
*/
private final int maxCount = totalSize - 1;
/**
* Create an iterator
* @see #iterator()
*/
Iterator() {
counter[last] = -1;
}
/**
* {@inheritDoc}
*/
public boolean hasNext() {
return count < maxCount;
}
/**
* @return the unidimensional count after the counter has been
* incremented by {@code 1}.
* @throws NoSuchElementException if {@link #hasNext()} would have
* returned {@code false}.
*/
public Integer next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
for (int i = last; i >= 0; i--) {
if (counter[i] == size[i] - 1) {
counter[i] = 0;
} else {
++counter[i];
break;
}
}
return ++count;
}
/**
* Get the current unidimensional counter slot.
*
* @return the index within the unidimensionl counter.
*/
public int getCount() {
return count;
}
/**
* Get the current multidimensional counter slots.
*
* @return the indices within the multidimensional counter.
*/
public int[] getCounts() {
return MathArrays.copyOf(counter);
}
/**
* Get the current count in the selected dimension.
*
* @param dim Dimension index.
* @return the count at the corresponding index for the current state
* of the iterator.
* @throws IndexOutOfBoundsException if {@code index} is not in the
* correct interval (as defined by the length of the argument in the
* {@link MultidimensionalCounter#MultidimensionalCounter(int[])
* constructor of the enclosing class}).
*/
public int getCount(int dim) {
return counter[dim];
}
/**
* @throws UnsupportedOperationException
*/
public void remove() {
throw new UnsupportedOperationException();
}
}
/**
* Create a counter.
*
* @param size Counter sizes (number of slots in each dimension).
* @throws NotStrictlyPositiveException if one of the sizes is
* negative or zero.
*/
public MultidimensionalCounter(int ... size) throws NotStrictlyPositiveException {
dimension = size.length;
this.size = MathArrays.copyOf(size);
uniCounterOffset = new int[dimension];
last = dimension - 1;
int tS = size[last];
for (int i = 0; i < last; i++) {
int count = 1;
for (int j = i + 1; j < dimension; j++) {
count *= size[j];
}
uniCounterOffset[i] = count;
tS *= size[i];
}
uniCounterOffset[last] = 0;
if (tS <= 0) {
throw new NotStrictlyPositiveException(tS);
}
totalSize = tS;
}
/**
* Create an iterator over this counter.
*
* @return the iterator.
*/
public Iterator iterator() {
return new Iterator();
}
/**
* Get the number of dimensions of the multidimensional counter.
*
* @return the number of dimensions.
*/
public int getDimension() {
return dimension;
}
/**
* Convert to multidimensional counter.
*
* @param index Index in unidimensional counter.
* @return the multidimensional counts.
* @throws OutOfRangeException if {@code index} is not between
* {@code 0} and the value returned by {@link #getSize()} (excluded).
*/
public int[] getCounts(int index) throws OutOfRangeException {
if (index < 0 ||
index >= totalSize) {
throw new OutOfRangeException(index, 0, totalSize);
}
final int[] indices = new int[dimension];
int count = 0;
for (int i = 0; i < last; i++) {
int idx = 0;
final int offset = uniCounterOffset[i];
while (count <= index) {
count += offset;
++idx;
}
--idx;
count -= offset;
indices[i] = idx;
}
indices[last] = index - count;
return indices;
}
/**
* Convert to unidimensional counter.
*
* @param c Indices in multidimensional counter.
* @return the index within the unidimensionl counter.
* @throws DimensionMismatchException if the size of {@code c}
* does not match the size of the array given in the constructor.
* @throws OutOfRangeException if a value of {@code c} is not in
* the range of the corresponding dimension, as defined in the
* {@link MultidimensionalCounter#MultidimensionalCounter(int...) constructor}.
*/
public int getCount(int ... c)
throws OutOfRangeException, DimensionMismatchException {
if (c.length != dimension) {
throw new DimensionMismatchException(c.length, dimension);
}
int count = 0;
for (int i = 0; i < dimension; i++) {
final int index = c[i];
if (index < 0 ||
index >= size[i]) {
throw new OutOfRangeException(index, 0, size[i] - 1);
}
count += uniCounterOffset[i] * c[i];
}
return count + c[last];
}
/**
* Get the total number of elements.
*
* @return the total size of the unidimensional counter.
*/
public int getSize() {
return totalSize;
}
/**
* Get the number of multidimensional counter slots in each dimension.
*
* @return the sizes of the multidimensional counter in each dimension.
*/
public int[] getSizes() {
return MathArrays.copyOf(size);
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
final StringBuilder sb = new StringBuilder();
for (int i = 0; i < dimension; i++) {
sb.append("[").append(getCount(i)).append("]");
}
return sb.toString();
}
}