--- /dev/null
+/*
+ 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 Leo.G@seznam.cz
+ 4. Products derived from this software may not be called "Egothor",
+ nor may "Egothor" appear in their name, without prior written
+ permission from Leo.G@seznam.cz.
+
+ 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
+ BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ 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 (Leo.G@seznam.cz).
+ */
+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.
+ * <p>
+ * Lift's <i>raison d'etre</i> 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 <tt>true</tt>, 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<CharSequence> cmds = orig.cmds;
+ List<Row> rows = new ArrayList<Row>();
+ List<Row> 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<Row>(), remap);
+
+ return new Trie(orig.forward, remap[orig.root], cmds, rows);
+ }
+
+ /**
+ * Reduce the trie using Lift-Up reduction.
+ * <p>
+ * 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<Row> nodes) {
+ Iterator<Cell> 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;
+ }
+ }
+ }
+ }
+ }
+ }
+}
fnp / pylucene.git / blobdiff