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A comprehensive collection of matrix data structures, linear solvers, least squares methods,
eigenvalue, and singular value decompositions.
/*
* Copyright (C) 2003-2006 Bjørn-Ove Heimsund
*
* This file is part of MTJ.
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by the
* Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package no.uib.cipr.matrix.sparse;
/**
* Array utilities. Complements java.util.Arrays
*/
class Arrays {
private Arrays() {
// No need to instantiate
}
/**
* Searches for a key in a sorted array, and returns an index to an element
* which is greater than or equal key.
*
* @param index
* Sorted array of integers
* @param key
* Search for something equal or greater
* @param begin
* Start posisiton in the index
* @param end
* One past the end position in the index
* @return end if nothing greater or equal was found, else an index
* satisfying the search criteria
*/
public static int binarySearchGreater(int[] index, int key, int begin,
int end) {
return binarySearchInterval(index, key, begin, end, true);
}
/**
* Searches for a key in a sorted array, and returns an index to an element
* which is greater than or equal key.
*
* @param index
* Sorted array of integers
* @param key
* Search for something equal or greater
* @return index.length if nothing greater or equal was found, else an index
* satisfying the search criteria
*/
public static int binarySearchGreater(int[] index, int key) {
return binarySearchInterval(index, key, 0, index.length, true);
}
/**
* Searches for a key in a sorted array, and returns an index to an element
* which is smaller than or equal key.
*
* @param index
* Sorted array of integers
* @param key
* Search for something equal or greater
* @param begin
* Start posisiton in the index
* @param end
* One past the end position in the index
* @return begin-1 if nothing smaller or equal was found, else an index
* satisfying the search criteria
*/
public static int binarySearchSmaller(int[] index, int key, int begin,
int end) {
return binarySearchInterval(index, key, begin, end, false);
}
/**
* Searches for a key in a sorted array, and returns an index to an element
* which is smaller than or equal key.
*
* @param index
* Sorted array of integers
* @param key
* Search for something equal or greater
* @return -1 if nothing smaller or equal was found, else an index
* satisfying the search criteria
*/
public static int binarySearchSmaller(int[] index, int key) {
return binarySearchInterval(index, key, 0, index.length, false);
}
/**
* Searches for a key in a subset of a sorted array.
*
* @param index
* Sorted array of integers
* @param key
* Key to search for
* @param begin
* Start posisiton in the index
* @param end
* One past the end position in the index
* @return Integer index to key. -1 if not found
*/
public static int binarySearch(int[] index, int key, int begin, int end) {
end--;
while (begin <= end) {
int mid = (end + begin) >> 1;
if (index[mid] < key)
begin = mid + 1;
else if (index[mid] > key)
end = mid - 1;
else
return mid;
}
return -1;
}
private static int binarySearchInterval(int[] index, int key, int begin,
int end, boolean greater) {
// Zero length array?
if (begin == end)
if (greater)
return end;
else
return begin - 1;
end--; // Last index
int mid = (end + begin) >> 1;
// The usual binary search
while (begin <= end) {
mid = (end + begin) >> 1;
if (index[mid] < key)
begin = mid + 1;
else if (index[mid] > key)
end = mid - 1;
else
return mid;
}
// No direct match, but an inf/sup was found
if ((greater && index[mid] >= key) || (!greater && index[mid] <= key))
return mid;
// No inf/sup, return at the end of the array
else if (greater)
return mid + 1; // One past end
else
return mid - 1; // One before start
}
/**
* Finds the number of repeated entries
*
* @param num
* Maximum index value
* @param ind
* Indices to check for repetitions
* @return Array of length num with the number of repeated
* indices of ind
*/
public static int[] bandwidth(int num, int[] ind) {
int[] nz = new int[num];
for (int i = 0; i < ind.length; ++i)
nz[ind[i]]++;
return nz;
}
}