org.egothor.stemmer.Lift Maven / Gradle / Ivy
/*
Egothor Software License version 1.00
Copyright (C) 1997-2004 Leo Galambos.
Copyright (C) 2002-2004 "Egothor developers"
on behalf of the Egothor Project.
All rights reserved.
This software is copyrighted by the "Egothor developers". If this
license applies to a single file or document, the "Egothor developers"
are the people or entities mentioned as copyright holders in that file
or document. If this license applies to the Egothor project as a
whole, the copyright holders are the people or entities mentioned in
the file CREDITS. This file can be found in the same location as this
license in the distribution.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
1. Redistributions of source code must retain the above copyright
notice, the list of contributors, this list of conditions, and the
following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, the list of contributors, this list of conditions, and the
disclaimer that follows these conditions in the documentation
and/or other materials provided with the distribution.
3. The name "Egothor" must not be used to endorse or promote products
derived from this software without prior written permission. For
written permission, please contact [email protected]
4. Products derived from this software may not be called "Egothor",
nor may "Egothor" appear in their name, without prior written
permission from [email protected].
In addition, we request that you include in the end-user documentation
provided with the redistribution and/or in the software itself an
acknowledgement equivalent to the following:
"This product includes software developed by the Egothor Project.
http://egothor.sf.net/"
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE EGOTHOR PROJECT OR ITS CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
This software consists of voluntary contributions made by many
individuals on behalf of the Egothor Project and was originally
created by Leo Galambos ([email protected]).
*/
package org.egothor.stemmer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
/**
* The Lift class is a data structure that is a variation of a Patricia trie.
*
* Lift's raison d'etre is to implement reduction of the trie via the
* Lift-Up method., which makes the data structure less liable to overstemming.
*/
public class Lift extends Reduce {
boolean changeSkip;
/**
* Constructor for the Lift object.
*
* @param changeSkip when set to true, comparison of two Cells takes
* a skip command into account
*/
public Lift(boolean changeSkip) {
this.changeSkip = changeSkip;
}
/**
* Optimize (eliminate rows with no content) the given Trie and return the
* reduced Trie.
*
* @param orig the Trie to optimized
* @return the reduced Trie
*/
@Override
public Trie optimize(Trie orig) {
List cmds = orig.cmds;
List rows = new ArrayList();
List orows = orig.rows;
int remap[] = new int[orows.size()];
for (int j = orows.size() - 1; j >= 0; j--) {
liftUp(orows.get(j), orows);
}
Arrays.fill(remap, -1);
rows = removeGaps(orig.root, orows, new ArrayList(), remap);
return new Trie(orig.forward, remap[orig.root], cmds, rows);
}
/**
* Reduce the trie using Lift-Up reduction.
*
* The Lift-Up reduction propagates all leaf-values (patch commands), where
* possible, to higher levels which are closer to the root of the trie.
*
* @param in the Row to consider when optimizing
* @param nodes contains the patch commands
*/
public void liftUp(Row in, List nodes) {
Iterator| i = in.cells.values().iterator();
for (; i.hasNext();) {
Cell c = i.next();
if (c.ref >= 0) {
Row to = nodes.get(c.ref);
int sum = to.uniformCmd(changeSkip);
if (sum >= 0) {
if (sum == c.cmd) {
if (changeSkip) {
if (c.skip != to.uniformSkip + 1) {
continue;
}
c.skip = to.uniformSkip + 1;
} else {
c.skip = 0;
}
c.cnt += to.uniformCnt;
c.ref = -1;
} else if (c.cmd < 0) {
c.cnt = to.uniformCnt;
c.cmd = sum;
c.ref = -1;
if (changeSkip) {
c.skip = to.uniformSkip + 1;
} else {
c.skip = 0;
}
}
}
}
}
}
}
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