/** Build the cluster's label from suffix tree edge indices. */
private String buildLabel(int[] phraseIndices) {
final boolean joinWithSpace =
context.language.getLanguageCode() != LanguageCode.CHINESE_SIMPLIFIED;
// Count the number of terms first.
int termsCount = 0;
for (int j = 0; j < phraseIndices.length; j += 2) {
termsCount += phraseIndices[j + 1] - phraseIndices[j] + 1;
}
// Extract terms info for the phrase and construct the label.
final boolean[] stopwords = new boolean[termsCount];
final char[][] images = new char[termsCount][];
final short[] tokenTypes = context.allWords.type;
int k = 0;
for (int i = 0; i < phraseIndices.length; i += 2) {
for (int j = phraseIndices[i]; j <= phraseIndices[i + 1]; j++, k++) {
final int termIndex = sb.input.get(j);
images[k] = context.allWords.image[termIndex];
stopwords[k] = TokenTypeUtils.isCommon(tokenTypes[termIndex]);
}
}
return LabelFormatter.format(images, stopwords, joinWithSpace);
}
/** Calculate "effective phrase length", that is the number of non-ignored words in the phrase. */
final int effectivePhraseLength(IntStack path) {
final int[] terms = sb.input.buffer;
final int lower = ignoreWordIfInFewerDocs;
final int upper = (int) (ignoreWordIfInHigherDocsPercent * documents.size());
int effectivePhraseLen = 0;
for (int i = 0; i < path.size(); i += 2) {
for (int j = path.get(i); j <= path.get(i + 1); j++) {
final int termIndex = terms[j];
// If this term is a stop word, don't count it.
if (TokenTypeUtils.isCommon(context.allWords.type[termIndex])) {
continue;
}
// If this word occurs in more than a given fraction of the input
// collection don't count it.
final int docCount = context.allWords.tfByDocument[termIndex].length / 2;
if (docCount < lower || docCount > upper) {
continue;
}
effectivePhraseLen++;
}
}
return effectivePhraseLen;
}
/** Collect all unique non-stop word from a phrase. */
private void appendUniqueWords(IntStack words, IntStack offsets, PhraseCandidate p) {
assert p.cluster.phrases.size() == 1;
final int start = words.size();
final int[] phraseIndices = p.cluster.phrases.get(0);
final short[] tokenTypes = context.allWords.type;
for (int i = 0; i < phraseIndices.length; i += 2) {
for (int j = phraseIndices[i]; j <= phraseIndices[i + 1]; j++) {
final int termIndex = sb.input.get(j);
if (!TokenTypeUtils.isCommon(tokenTypes[termIndex])) {
words.push(termIndex);
}
}
}
// Sort words, we don't care about their order when counting subsets.
Arrays.sort(words.buffer, start, words.size());
// Reorder to keep only unique words.
int j = start;
for (int i = start + 1; i < words.size(); i++) {
if (words.buffer[j] != words.buffer[i]) {
words.buffer[++j] = words.buffer[i];
}
}
words.elementsCount = j + 1;
offsets.push(start, words.size() - start);
}
/**
* Computes stem indices of words that are one-word label candidates or are non-stop words from
* phrase label candidates.
*/
private int[] computeRequiredStemIndices(PreprocessingContext context) {
final int[] labelsFeatureIndex = context.allLabels.featureIndex;
final int[] wordsStemIndex = context.allWords.stemIndex;
final short[] wordsTypes = context.allWords.type;
final int[][] phrasesWordIndices = context.allPhrases.wordIndices;
final int wordCount = wordsStemIndex.length;
final int[][] stemsTfByDocument = context.allStems.tfByDocument;
int documentCount = context.documents.size();
final BitSet requiredStemIndices = new BitSet(labelsFeatureIndex.length);
for (int i = 0; i < labelsFeatureIndex.length; i++) {
final int featureIndex = labelsFeatureIndex[i];
if (featureIndex < wordCount) {
addStemIndex(
wordsStemIndex, documentCount, stemsTfByDocument, requiredStemIndices, featureIndex);
} else {
final int[] wordIndices = phrasesWordIndices[featureIndex - wordCount];
for (int j = 0; j < wordIndices.length; j++) {
final int wordIndex = wordIndices[j];
if (!TokenTypeUtils.isCommon(wordsTypes[wordIndex])) {
addStemIndex(
wordsStemIndex, documentCount, stemsTfByDocument, requiredStemIndices, wordIndex);
}
}
}
}
return requiredStemIndices.asIntLookupContainer().toArray();
}
/**
* Consider certain special cases of internal suffix tree nodes. The suffix tree may contain
* internal nodes with paths starting or ending with a stop word (common word). We have the
* following interesting scenarios:
*
* <dl>
* <dt>IF LEADING STOPWORD: IGNORE THE NODE.
* <dd>There MUST be a phrase with this stopword chopped off in the suffix tree (a suffix of
* this phrase) and its frequency will be just as high.
* <dt>IF TRAILING STOPWORDS:
* <dd>Check if the edge leading to the current node is composed entirely of stopwords. If so,
* there must be a parent node that contains non-stopwords and we can ignore the current
* node. Otherwise we can chop off the trailing stopwords from the current node's phrase
* (this phrase cannot be duplicated anywhere in the tree because if it were, there would
* have to be a branch somewhere in the suffix tree on the edge).
* </dl>
*/
final boolean checkAcceptablePhrase(IntStack path) {
assert path.size() > 0;
final int[] terms = sb.input.buffer;
final short[] tokenTypes = context.allWords.type;
// Ignore nodes that start with a stop word.
if (TokenTypeUtils.isCommon(tokenTypes[terms[path.get(0)]])) {
return false;
}
// Check the last edge of the current node.
int i = path.get(path.size() - 2);
int j = path.get(path.size() - 1);
final int k = j;
while (i <= j && TokenTypeUtils.isCommon(tokenTypes[terms[j]])) {
j--;
}
if (j < i) {
// If the edge contains only stopwords, ignore the node.
return false;
} else if (j < k) {
// There have been trailing stop words on the edge. Chop them off.
path.buffer[path.size() - 1] = j;
}
// Check the total phrase length (in words, including stopwords).
int termsCount = 0;
for (j = 0; j < path.size(); j += 2) {
termsCount += path.get(j + 1) - path.get(j) + 1;
}
if (termsCount > maxDescPhraseLength) {
return false;
}
return true;
}
/** Collect all words from a phrase. */
private void appendWords(IntStack words, IntStack offsets, PhraseCandidate p) {
final int start = words.size();
final int[] phraseIndices = p.cluster.phrases.get(0);
final short[] tokenTypes = context.allWords.type;
for (int i = 0; i < phraseIndices.length; i += 2) {
for (int j = phraseIndices[i]; j <= phraseIndices[i + 1]; j++) {
final int termIndex = sb.input.get(j);
if (!TokenTypeUtils.isCommon(tokenTypes[termIndex])) {
words.push(termIndex);
}
}
}
offsets.push(start, words.size() - start);
}
/**
* Build a cluster's label from suffix tree edge indices, including some debugging and diagnostic
* information.
*/
@SuppressWarnings("unused")
private String buildDebugLabel(int[] phraseIndices) {
final StringBuilder b = new StringBuilder();
String sep = "";
int k = 0;
final short[] tokenTypes = context.allWords.type;
for (int i = 0; i < phraseIndices.length; i += 2) {
for (int j = phraseIndices[i]; j <= phraseIndices[i + 1]; j++, k++) {
b.append(sep);
final int termIndex = sb.input.get(j);
b.append(context.allWords.image[termIndex]);
if (TokenTypeUtils.isCommon(tokenTypes[termIndex])) b.append("[S]");
sep = " ";
}
sep = "_";
}
return b.toString();
}
