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/*
* LingPipe v. 4.1.0
* Copyright (C) 2003-2011 Alias-i
*
* This program is licensed under the Alias-i Royalty Free License
* Version 1 WITHOUT ANY WARRANTY, without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Alias-i
* Royalty Free License Version 1 for more details.
*
* You should have received a copy of the Alias-i Royalty Free License
* Version 1 along with this program; if not, visit
* http://alias-i.com/lingpipe/licenses/lingpipe-license-1.txt or contact
* Alias-i, Inc. at 181 North 11th Street, Suite 401, Brooklyn, NY 11211,
* +1 (718) 290-9170.
*/
package com.aliasi.crf;
import com.aliasi.tag.MarginalTagger;
import com.aliasi.tag.NBestTagger;
import com.aliasi.tag.ScoredTagging;
import com.aliasi.tag.Tagger;
import com.aliasi.tag.Tagging;
import com.aliasi.tag.TagLattice;
import com.aliasi.corpus.Corpus;
import com.aliasi.corpus.ObjectHandler;
import com.aliasi.features.Features;
import com.aliasi.io.Reporter;
import com.aliasi.io.Reporters;
import com.aliasi.matrix.DenseVector;
import com.aliasi.matrix.Matrices;
import com.aliasi.matrix.SparseFloatVector;
import com.aliasi.matrix.Vector;
import com.aliasi.stats.AnnealingSchedule;
import com.aliasi.stats.RegressionPrior;
import com.aliasi.symbol.MapSymbolTable;
import com.aliasi.symbol.SymbolTable;
import com.aliasi.util.AbstractExternalizable;
import com.aliasi.util.BoundedPriorityQueue;
import com.aliasi.util.Exceptions;
import com.aliasi.util.FeatureExtractor;
import com.aliasi.util.Iterators;
import com.aliasi.util.ObjectToCounterMap;
import com.aliasi.util.Scored;
import com.aliasi.util.ScoredObject;
import com.aliasi.util.Strings;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.io.Serializable;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Formatter;
import java.util.HashMap;
import java.util.IllegalFormatException;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
/**
* The {@code ChainCrf} class implements linear chain conditional
* random field decoding and estimation for input token sequences of
* type {@code E}.
*
* The cliques of the graphical model are typically called nodes
* and edges in a chain CRF. A node consists of a token position,
* the rest of the input tokens, whereas an edge adds the previous
* tag. A CRF feature extractor converts nodes and edges to
* feature maps, which are then converted to vectors for use in
* CRFs.
*
*
Components of Linear Chain Conditional Random Fields
*
* A linear-chain conditional random field (CRF) assigns tags to each
* element of an input sequence of items, which we call tokens. The
* inputs may be strings, or any kind of structured objects.
*
* First, we suppose a fixed, finite set of {@code K} tags {@code
* tags[0],...,tags[K-1]} which may be assigned to tokens as part of a
* tagging. The coeffcient matrix β consists of
* {@code K} coefficient vectors,
* β[0],...,β[K-1], one for each tag.
*
*
Second, we assume a pair of feature extractors, one for nodes in
* the graphical model and one for edges. The node feature extractor
* φ0 maps sequences {@code xs} of input
* tokens and a position {@code n} in that sequence ({@code 0 <= n <
* xs.length}) into a feature map φ0(xs,n).
*
*
The edge feature extractor φ1 maps
* input token sequences {@code xs}, a position {@code n} in that
* sequence, and previous tag {@code tags[k]} to a feature
* map φ1(xs,n,tags[k]).
*
* The combined features extracted for input token sequence {@code
* xs}, position {@code n} in that sequence, and tag {@code tags[k]} are:
* defined by:
*
*
φ(xs,0,tags[k]) = φ0(xs,0)
* φ(xs,n,tags[k]) = φ0(xs,n) + φ1(xs,n,tags[k]) for n > 0
*
* The special case for position 0 is because there is no previous
* tag. Note that boundary features (begin-of-sequence, end-of-sequence)
* may be defined in φ0 because it knows
* the position and length of input.
*
* Tag Sequence Probability
*
* The probability model assumes a fixed sequence of input tokens
* {@code xs[0],...,xs[N-1]} of length {@code N}. The model assigns
* a conditional probability to sequences of tag indices
* {@code ys[0],...,ys[N-1]} (where {@code 0 <= ys[n] < tags.length}),
* by:
*
*
* p(ys|ws) ∝ exp(Σn < N φ(xs,n,tags[ys[n-1]])⋅β[ys[n]])
*
* where the sum is over the dot product of the feature vector
* φ(xs,n,tags[ys[n-1]]) extracted for the input
* sequence of tokens {@code xs} at position {@code n} and
* previous tag {@code tags[ys[n-1]]} with index {@code ys[n-1]},
* and the coefficient for output tag {@code tags[ys[n]]},
* namely β[tags[ys[n]].
*
* Note on Factored Coefficients
*
* Note that this presentation of CRFs is a bit non-standard. In
* particular, LingPipe has factored what is usually a single large
* coefficient vector into one vector per output tag. This somewhat
* restricts the kinds of features that may be extracted so that each
* feature depends on a specific output tag. The reason this is done
* is for efficiency. Note that the node feature extractor
* φ0(xs,n) could be rolled into the more
* general edge feature extractor
* φ1(xs,n,t); the node feature extractor
* is only for efficiency, allowing features shared for all previous
* tags t to be extracted only once.
*
*
Legal Tags: Structural Zeros
*
* The more verbose constructor for chain CRFs takes three array
* arguments which indicate which tags are legal in which positions.
* The shorter convenience constructor implicitly assumes any tag may
* occur anywhere. The legal start tag array indicates if a tag may
* start a tagging. The legal end tag array indicates if a tag may
* be the last tag in a tagging. The legal transition array indicates
* for a pair of tags if one may follow the other.
*
*
These are typically used when chunkers are encoded as taggers,
* and some sequences of tags are structurally illegal. These are
* called structural zeros in statistical modeling terms.
*
*
During estimation, these may be computed by specifying
*
*
*
First-Best Output: Viterbi
*
* First-best output is calculated very efficiently in linear time
* in the size of the inputs using the Viterbi algorithm, a form
* of dynamic programming applicable to sequence tagging. Note that
* the normalizing constant does not need to be computed. This
* functionality is avaiable through the method {@link #tag(List)}
* of the {@link Tagger} interface.
*
* N-Best Sequence Output: Viterbi Forward, A* Backward
*
* N-best output may be calculated in one linear forward pass and an
* efficient backward pass. The forward pass computes and stores the
* full Viterbi lattice consisting of the best analysis and score up
* to a given token for a given tag. The backward pass uses the
* A* algorithm with the Viterbi scores as exact completion
* estimates. This allows n-best analyses to be returned in
* order, with at most a constant amount of work per result.
*
* N-best functionality is available through the method
* {@link #tagNBest(List,int)} of the {@link NBestTagger}
* interface. This returns an iterator over scored tagging
* instances. The scores are the unnormalized products defined
* above.
*
*
N-best functionality with scores normalized to conditional
* probabilities may be computed using {@link
* #tagNBestConditional(List,int)}. This requires computing the
* normalizing constant using the forward-backward algorithm described
* in the next section.
*
*
Marginal Tag Probabiilty Output: Forward-Backward Algorithm
*
* The forward-backward algorithm may be applied to conditional random
* fields. The generalized undirected graphical model form of this
* algorithm is known as the product-sum algorithm. The result is
* returned as an instance of {@link TagLattice}.
*
* The forward-backward algorithm efficiently computes unnormalized
* forward, backward, and normalizing probabilities. As defined
* in the {@link TagLattice} class documentation, these
* may be used to define the probability of a tag or tag sequence
* staring at a specified position given the input tokens.
*
*
The unnormalized total probability Z may be used with
* n-best output to convert n-best sequence scores into conditional
* probabilities of the tagging given the input tokens.
*
*
Stochastic Gradient Descent Training
*
* Training is carried out for conditional random fields the same
* way as for logistic regression classifiers (see {@link
* com.aliasi.classify.LogisticRegressionClassifier} and {@link
* com.aliasi.stats.LogisticRegression}. It's mathematically
* identical to think of CRFs as multi-way classifiers where the
* categories are sequences of tags. Under that analogy, training for
* conditional random fields exactly mirrors that for logistic
* regression. The only difference for conditional random fields is
* that the expectations at each step are computed using the
* forward-backward algorithm and efficiently applied over the
* lattice.
*
*
See the logistic regression classes for a description of the
* prior (also see {@link RegressionPrior}), and the learning and
* annealing rate (also see {@link AnnealingSchedule}).
*
*
Reporting is exactly the same for conditional random fields as
* for logistic regression, with each epoch reporting learning rate
* (lr), log likelihood (ll), log prior probability (lp), and the
* combined objective being optimized consisting of the sum of log
* likelihood and log prior probability (llp), and the best combined
* objective so far (llp*).
*
*
Unlike in logistic regression, the prior is applied according
* to a blocking strategy rather than through lazy updates. The block
* size is a parameter that determines how often the prior gradient
* is applied. In effect, it treats updates as blocks. The weight of
* the prior is adjusted accordingly. After all of the instances in
* an epoch, the prior is applied one more time to ensure that the
* coefficients are in the right state after each epoch.
*
*
Significant speedups can be achieved by setting the feature
* caching flag in the estimator method to {@code true}. This may
* require a large amount of memory, because it stores the entire
* lattice of vectors for each training instance.
*
*
Serialization
*
* A chain CRF may be serialized if its parts are serializable: the
* node and edge feature extractor, the feature symbol table, and the
* vector coefficients.
*
* The CRF read back in will be identical to the one that was
* serialized to the extent that the parts are equivalent: feature
* extractors, symbol table, and coefficients.
*
*
For CRFs estimated using the gradient descent estimator method,
* the symbol table and vector coefficients are serializable in such a
* way as to reproduce equivalent objects to the ones being
* serialized.
*
*
Thread Safety
*
* A CRF is thread safe to the extent that its symbol table and
* feature extractors are thread safe. Calling the tagging methods
* concurrently will result in concurrent calls to feature extractors
* and symbol tables. The standard symbol table implementations are
* all thread safe, and almost all well-implemented feature extractors
* will be thread safe.
*
* @author Bob Carpenter
* @version 3.9.2
* @since LingPipe3.9
* @param Type of tokens in the tagging.
*/
public class ChainCrf
implements Tagger,
NBestTagger,
MarginalTagger,
Serializable {
static final long serialVersionUID = -4868542587460878290L;
private final List mTagList;
private final boolean[] mLegalTagStarts;
private final boolean[] mLegalTagEnds;
private final boolean[][] mLegalTagTransitions;
private final Vector[] mCoefficients;
private final SymbolTable mFeatureSymbolTable;
private final ChainCrfFeatureExtractor mFeatureExtractor;
private final boolean mAddInterceptFeature;
private final int mNumDimensions;
/**
* Construct a conditional random field from the specified tags,
* feature vector coefficients, symbol table for feature, feature
* extractors and flag indicating whether to add intercepts or
* not.
*
* @param tags Array of output tags.
* @param coefficients Array of coefficient vectors parallel to tags.
* @param featureSymbolTable Symbol table for feature extraction
* to vectors.
* @param featureExtractor CRF feature extractor.
* @param addInterceptFeature {@code true} if an intercept feature
* at position 0 with value 1 is added to all feature vectors.
* @throws IllegalArgumentException If the tag and coefficient
* vector arrays are not non-empty and the same length, or if the
* coefficient vectors are not all of the same number of dimensions.
*/
public ChainCrf(String[] tags,
Vector[] coefficients,
SymbolTable featureSymbolTable,
ChainCrfFeatureExtractor featureExtractor,
boolean addInterceptFeature) {
this(tags,
trueArray(tags.length),
trueArray(tags.length),
trueArray(tags.length,tags.length),
coefficients,
featureSymbolTable,
featureExtractor,
addInterceptFeature);
}
/**
* Construct a conditional random field from the specified tags,
* feature vector coefficients, symbol table for feature, feature
* extractors and flag indicating whether to add intercepts or
* not.
*
* @param tags Array of output tags
* @param legalTagStarts Array of flags indicating if tag may be
* first tag for a tagging.
* @param legalTagEnds Array of flags indicating if tag may be
* last tag for a tagging.
* @param legalTagTransitions Two dimensional array of flags indicating
* if the first tag may be followed by the second tag.
* @param coefficients Array of coefficient vectors parallel to tags.
* @param featureSymbolTable Symbol table for feature extraction
* to vectors.
* @param featureExtractor CRF feature extractor.
* @param addInterceptFeature {@code true} if an intercept feature
* at position 0 with value 1 is added to all feature vectors.
* @throws IllegalArgumentException If the tag and coefficient
* vector arrays are not non-empty and the same length, or if the
* coefficient vectors are not all of the same number of dimensions.
*/
public ChainCrf(String[] tags,
boolean[] legalTagStarts,
boolean[] legalTagEnds,
boolean[][] legalTagTransitions,
Vector[] coefficients,
SymbolTable featureSymbolTable,
ChainCrfFeatureExtractor featureExtractor,
boolean addInterceptFeature) {
if (tags.length < 1) {
String msg = "Require at least one tag.";
}
if (tags.length != coefficients.length) {
String msg = "Require tags and coefficients to be same length."
+ " Found tags.length=" + tags.length
+ " coefficients.length=" + coefficients.length;
throw new IllegalArgumentException(msg);
}
if (tags.length != legalTagStarts.length) {
String msg = "Tags and starts must be same length."
+ " Found tags.length=" + tags.length
+ " legalTagStarts.length=" + legalTagStarts.length;
throw new IllegalArgumentException(msg);
}
if (tags.length != legalTagEnds.length) {
String msg = "Tags and starts must be same length."
+ " Found tags.length=" + tags.length
+ " legalTagStarts.length=" + legalTagStarts.length;
throw new IllegalArgumentException(msg);
}
if (tags.length != legalTagTransitions.length) {
String msg = "Tags and transitions must be same length."
+ " Found tags.length=" + tags.length
+ " legalTagTransitions.length=" + legalTagTransitions.length;
throw new IllegalArgumentException(msg);
}
for (int i = 0; i < legalTagTransitions.length; ++i) {
if (tags.length != legalTagTransitions[i].length) {
String msg = "Tags and transition rows must be same length."
+ " Found tags.length=" + tags.length
+ " legalTagTransitions[" + i + "].length="
+ legalTagTransitions[i].length;
throw new IllegalArgumentException(msg);
}
}
for (int k = 1; k < coefficients.length; ++k) {
if (coefficients[0].numDimensions() != coefficients[k].numDimensions()) {
String msg = "All coefficients must be same length."
+ " Found coefficents[0].numDimensions()="
+ coefficients[0].numDimensions()
+ " coefficients[" + k + "].numDimensions()="
+ coefficients[k].numDimensions();
throw new IllegalArgumentException(msg);
}
}
mTagList = Arrays.asList(tags);
mLegalTagStarts = legalTagStarts;
mLegalTagEnds = legalTagEnds;
mLegalTagTransitions = legalTagTransitions;
mCoefficients = coefficients;
mNumDimensions = coefficients[0].numDimensions();
mFeatureSymbolTable = featureSymbolTable;
mFeatureExtractor = featureExtractor;
mAddInterceptFeature = addInterceptFeature;
}
// Constructor Arguments
/**
* Returns an unmodifiable view of the array of tags underlying this CRF.
*
* The array of coefficient vectors is parallel to the array of
* tags returned by {@link #tags()}k, so the coefficient vector
* {@code coefficients()[n]} is for output tag {@code tags()[n]}.
*
* @return View of the output tags.
*/
public List tags() {
return Collections.unmodifiableList(mTagList);
}
/**
* Returns the tag for the specified tag index. This uses the
* underlying tags, so that {@code tag(k) == tags()[k]}.
*
* @param k Position of tag.
* @return Tag for the specified position.
* @throws ArrayIndexOutOfBoundsException If the specified index
* is out of bounds for the tag array ({@code k < 0} or {@code k
* >= tags().length}).
*/
public String tag(int k) {
return mTagList.get(k);
}
/**
* Return the coefficient vectors for this CRF.
*
* The array of coefficient vectors is parallel to the array of
* tags returned by {@link #tags()}k, so the coefficient vector
* {@code coefficients()[n]} is for output tag {@code tags()[n]}.
*
* @return The coefficient vectors.
*/
public Vector[] coefficients() {
Vector[] result = new Vector[mCoefficients.length];
for (int k = 0; k < result.length; ++k)
result[k] = Matrices.unmodifiableVector(mCoefficients[k]);
return result;
}
/**
* Returns an unmodifiable view of the symbol table for features for
* this CRF.
*
* @return A view of the symbol table for features.
*/
public SymbolTable featureSymbolTable() {
return MapSymbolTable.unmodifiableView(mFeatureSymbolTable);
}
/**
* Return the feature extractor for this CRF.
*
* @return The feature extractor.
*/
public ChainCrfFeatureExtractor featureExtractor() {
return mFeatureExtractor;
}
/**
* Returns {@code true} if this CRF adds an intercept feature
* with value 1.0 at index 0 to all feature vectors.
*
* @return Whether this CRF adds an intercept feature.
*/
public boolean addInterceptFeature() {
return mAddInterceptFeature;
}
// Tagger
public Tagging tag(List tokens) {
int numTokens = tokens.size();
if (numTokens == 0)
return new Tagging(tokens, Collections.emptyList());
int numTags = mTagList.size();
int numDimensions = mFeatureSymbolTable.numSymbols();
double[][] bestScores = new double[numTokens][numTags];
int[][] backPointers = new int[numTokens-1][numTags];
ChainCrfFeatures features = mFeatureExtractor.extract(tokens,mTagList);
Vector nodeVector0 = nodeFeatures(0,features);
for (int k = 0; k < numTags; ++k)
bestScores[0][k]
= mLegalTagStarts[k]
? nodeVector0.dotProduct(mCoefficients[k])
: Double.NEGATIVE_INFINITY;
Vector[] edgeVectors = new Vector[numTags];
for (int n = 1; n < numTokens; ++n) {
Vector nodeVector = nodeFeatures(n,features);
for (int kMinus1 = 0; kMinus1 < numTags; ++kMinus1)
edgeVectors[kMinus1] = edgeFeatures(n,kMinus1,features); // mTagList.get(kMinus1));
for (int k = 0; k < numTags; ++k) {
if (n == (numTokens-1) && !mLegalTagEnds[k]) {
bestScores[n][k] = Double.NEGATIVE_INFINITY;
backPointers[n-1][k] = -1;
continue;
}
double bestScore = Double.NEGATIVE_INFINITY;
int backPtr = -1;
double nodeScore = nodeVector.dotProduct(mCoefficients[k]);
for (int kMinus1 = 0; kMinus1 < numTags; ++kMinus1) {
if (!mLegalTagTransitions[kMinus1][k])
continue;
double score = nodeScore
+ edgeVectors[kMinus1].dotProduct(mCoefficients[k])
+ bestScores[n-1][kMinus1];
if (score > bestScore) {
bestScore = score;
backPtr = kMinus1;
}
}
bestScores[n][k] = bestScore;
backPointers[n-1][k] = backPtr;
}
}
double bestScore = Double.NEGATIVE_INFINITY;
int bestFinalTag = -1;
for (int k = 0; k < numTags; ++k) {
if (bestScores[numTokens-1][k] > bestScore) {
bestScore = bestScores[numTokens-1][k];
bestFinalTag = k;
}
}
List tags = new ArrayList(numTokens);
int bestPreviousTag = bestFinalTag;
tags.add(mTagList.get(bestFinalTag));
for (int n = numTokens-1; --n >= 0; ) {
bestPreviousTag = backPointers[n][bestPreviousTag];
tags.add(mTagList.get(bestPreviousTag));
}
Collections.reverse(tags);
return new Tagging(tokens,tags);
}
// NBestTagger
public Iterator> tagNBest(List tokens, int maxResults) {
if (tokens.size() == 0) {
ScoredTagging scoredTagging
= new ScoredTagging(tokens,
Collections.emptyList(),
0.0); // unnormalized (arbitrary choice)
return Iterators.singleton(scoredTagging);
}
return new NBestIterator(tokens,false,maxResults);
}
public Iterator> tagNBestConditional(List tokens, int maxResults) {
if (tokens.size() == 0) {
ScoredTagging scoredTagging
= new ScoredTagging(tokens,
Collections.emptyList(),
0.0); // log prob norm
return Iterators.singleton(scoredTagging);
}
return new NBestIterator(tokens,true,maxResults);
}
// Marginal Tagger
public TagLattice tagMarginal(List tokens) {
if (tokens.size() == 0) {
return new ForwardBackwardTagLattice(tokens,
mTagList,
EMPTY_DOUBLE_2D_ARRAY,
EMPTY_DOUBLE_2D_ARRAY,
EMPTY_DOUBLE_3D_ARRAY,
0.0);
}
FeatureVectors features = features(tokens);
TagLattice lattice
= forwardBackward(tokens,features);
return lattice;
}
/**
* Return a string-based representation of this chain CRF.
* All information returned in this string representation is
* available programatically.
*
* Warning: The output is very verbose, including
* symbolic representations of all the coefficients.
*
* @return A string-based representation of this chain CRF.
*/
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("Feature Extractor=" + featureExtractor());
sb.append("\n");
sb.append("Add intercept=" + addInterceptFeature());
sb.append("\n");
List tags = tags();
sb.append("Tags=" + tags);
sb.append("\n");
Vector[] coeffs = coefficients();
SymbolTable symTab = featureSymbolTable();
sb.append("Coefficients=\n");
for (int i = 0; i < coeffs.length; ++i) {
sb.append(tags.get(i));
sb.append(" ");
int[] nzDims = coeffs[i].nonZeroDimensions();
for (int k = 0; k < nzDims.length; ++k) {
if (k > 0) sb.append(", ");
int d = nzDims[k];
sb.append(symTab.idToSymbol(d));
sb.append("=");
sb.append(coeffs[i].value(d));
}
sb.append("\n");
}
return sb.toString();
}
// for serialization
Object writeReplace() {
return new Serializer(this);
}
private Vector nodeFeatures(int position,
ChainCrfFeatures features) {
return Features.toVector(features.nodeFeatures(position),
mFeatureSymbolTable,
mNumDimensions,
mAddInterceptFeature);
}
private Vector edgeFeatures(int position, int lastTagIndex,
ChainCrfFeatures features) {
return Features.toVector(features.edgeFeatures(position,lastTagIndex),
mFeatureSymbolTable,
mNumDimensions,
mAddInterceptFeature);
}
private FeatureVectors features(List tokens) {
int numTags = mTagList.size();
int numDimensions = mFeatureSymbolTable.numSymbols();
if (tokens.size() == 0)
return null;
ChainCrfFeatures features
= mFeatureExtractor.extract(tokens,mTagList);
// nodeFeatureVectors[n] = phi0(tokens,n)
Vector[] nodeFeatureVectors
= new Vector[tokens.size()];
for (int n = 0; n < tokens.size(); ++n)
nodeFeatureVectors[n] = nodeFeatures(n,features);
// edgeFeatureVectorss[n-1][k] = phi1(tokens,n,tags[k])
Vector[][] edgeFeatureVectorss
= new Vector[tokens.size()-1][mTagList.size()];
for (int n = 1; n < tokens.size(); ++n) {
for (int k = 0; k < numTags; ++k) {
edgeFeatureVectorss[n-1][k] = edgeFeatures(n,k,features);
}
}
return new FeatureVectors(nodeFeatureVectors,
edgeFeatureVectorss);
}
TagLattice forwardBackward(List tokens,
FeatureVectors features) {
// assumes tokens.size() > 0
int numTokens = tokens.size();
int numTags = mTagList.size();
// potential0Bos[kTo] = phi0(0) * beta[kTo]
double[] logPotentials0Begin = new double[numTags];
for (int kTo = 0; kTo < numTags; ++kTo)
logPotentials0Begin[kTo]
= mLegalTagStarts[kTo]
? features.mNodeFeatureVectors[0].dotProduct(mCoefficients[kTo])
: Double.NEGATIVE_INFINITY;
// logPotentials[nTo-1][kFrom][kTo] = phi(nTo,kFrom) * beta[kTo]
double[][][] logPotentials = new double[numTokens-1][numTags][numTags];
for (double[][] logPotentials2 : logPotentials)
for (double[] logPotentials3 : logPotentials2)
Arrays.fill(logPotentials3,Double.NEGATIVE_INFINITY);
for (int nTo = 1; nTo < numTokens; ++nTo) {
for (int kTo = 0; kTo < numTags; ++kTo) {
if (nTo == (numTokens - 1) && !mLegalTagEnds[kTo])
continue;
double nodePotentialKTo
= features.mNodeFeatureVectors[nTo].dotProduct(mCoefficients[kTo]);
for (int kFrom = 0; kFrom < numTags; ++kFrom)
if (mLegalTagTransitions[kFrom][kTo])
logPotentials[nTo-1][kFrom][kTo]
= features.mEdgeFeatureVectorss[nTo-1][kFrom].dotProduct(mCoefficients[kTo])
+ nodePotentialKTo;
}
}
// logForwards[nTo][kTo]
double[] buf = new double[numTags];
double[][] logForwards = new double[numTokens][numTags];
for (int kTo = 0; kTo < numTags; ++kTo)
logForwards[0][kTo] = logPotentials0Begin[kTo]; // should just copy array
for (int nTo = 1; nTo < numTokens; ++nTo) {
for (int kTo = 0; kTo < numTags; ++kTo) {
for (int kFrom = 0; kFrom < numTags; ++kFrom) {
buf[kFrom] = logForwards[nTo-1][kFrom]
+ logPotentials[nTo-1][kFrom][kTo];
}
logForwards[nTo][kTo] = com.aliasi.util.Math.logSumOfExponentials(buf);
}
}
// logBackwards[nFrom][kFrom]
double[][] logBackwards = new double[numTokens][numTags];
// logBackwards[numTokens-1] = 0.0; // by init
for (int nFrom = numTokens-1; --nFrom >= 0; ) {
for (int kFrom = 0; kFrom < numTags; ++kFrom) {
for (int kTo = 0; kTo < numTags; ++kTo) {
buf[kTo] = logBackwards[nFrom+1][kTo]
+ logPotentials[nFrom][kFrom][kTo];
}
logBackwards[nFrom][kFrom] = com.aliasi.util.Math.logSumOfExponentials(buf);
}
}
double logZ = com.aliasi.util.Math.logSumOfExponentials(logForwards[numTokens-1]);
// don't need logPotentials with logFwds
return new ForwardBackwardTagLattice(tokens,
mTagList,
logForwards,
logBackwards,
logPotentials,
logZ,
false); // dummy arg to ignore
}
class NBestIterator extends Iterators.Buffered> {
final List mTokens;
final double mLogZ;
final double[][][] mTransitionScores;
final double[][] mViterbiScores;
final int[][] mBackPointers;
final BoundedPriorityQueue mPriorityQueue;
// get at least one token; otherwise, handled up at caller level
NBestIterator(List tokens, boolean normToConditional, int maxResults) {
mPriorityQueue
= new BoundedPriorityQueue(ScoredObject.comparator(),
maxResults);
mTokens = tokens;
int numTokens = tokens.size();
int numTags = mTagList.size();
mTransitionScores = new double[numTokens-1][numTags][numTags];
for (double[][] xss : mTransitionScores)
for (double[] xs : xss)
Arrays.fill(xs,Double.NEGATIVE_INFINITY);
mViterbiScores = new double[numTokens][numTags];
for (double[] xs : mViterbiScores)
Arrays.fill(xs,Double.NEGATIVE_INFINITY);
mBackPointers = new int[numTokens-1][numTags];
for (int[] ptrs : mBackPointers)
Arrays.fill(ptrs,-1);
Vector[] edgeVectors = new Vector[numTags];
ChainCrfFeatures features = mFeatureExtractor.extract(tokens,mTagList);
for (int n = 1; n < numTokens; ++n) {
Vector nodeVector = nodeFeatures(n,features);
for (int kMinus1 = 0; kMinus1 < numTags; ++kMinus1) {
if (n == 1 && !mLegalTagStarts[kMinus1])
continue;
edgeVectors[kMinus1] = edgeFeatures(n,kMinus1,features);
}
for (int k = 0; k < numTags; ++k) {
if (n == (numTokens-1) && !mLegalTagEnds[k])
continue;
double nodeScore = nodeVector.dotProduct(mCoefficients[k]);
for (int kMinus1 = 0; kMinus1 < numTags; ++kMinus1) {
if (!mLegalTagTransitions[kMinus1][k])
continue;
if (n == 1 && !mLegalTagStarts[kMinus1])
continue;
mTransitionScores[n-1][kMinus1][k]
= nodeScore
+ edgeVectors[kMinus1].dotProduct(mCoefficients[k]);
}
}
}
Vector nodeVector0 = nodeFeatures(0,features);
for (int k = 0; k < numTags; ++k) {
if (!mLegalTagStarts[k])
continue;
mViterbiScores[0][k]
= nodeVector0.dotProduct(mCoefficients[k]);
}
for (int n = 1; n < numTokens; ++n) {
for (int k = 0; k < numTags; ++k) {
if (n == (numTokens-1) && !mLegalTagEnds[k])
continue;
double bestScore = Double.NEGATIVE_INFINITY;
int backPtr = -1;
for (int kMinus1 = 0; kMinus1 < numTags; ++kMinus1) {
if (!mLegalTagTransitions[kMinus1][k])
continue;
double score = mViterbiScores[n-1][kMinus1]
+ mTransitionScores[n-1][kMinus1][k];
if (score > bestScore) {
bestScore = score;
backPtr = kMinus1;
}
}
mViterbiScores[n][k] = bestScore;
mBackPointers[n-1][k] = backPtr;
}
}
mLogZ = normToConditional ? logZ() : 0.0;
for (int k = 0; k < numTags; ++k) {
offer(mViterbiScores[numTokens-1][k],null,numTokens-1,k);
}
}
double logZ() {
double[] forwards = mViterbiScores[0].clone();
int numTags = forwards.length;
double[] previousForwards = new double[numTags];
double[] exps = new double[numTags];
for (int n = 0; n < mTransitionScores.length; ++n) {
double[] temp = previousForwards;
previousForwards = forwards;
forwards = temp;
for (int k = 0; k < numTags; ++k) {
for (int kMinus1 = 0; kMinus1 < numTags; ++kMinus1) {
exps[kMinus1] = previousForwards[kMinus1] + mTransitionScores[n][kMinus1][k];
}
forwards[k] = com.aliasi.util.Math.logSumOfExponentials(exps);
}
}
double logZ = com.aliasi.util.Math.logSumOfExponentials(forwards);
return logZ;
}
void offer(double score, ForwardPointer pointer, int n, int k) {
if (score == Double.NEGATIVE_INFINITY)
return;
if (pointer != null && pointer.mScore == Double.NEGATIVE_INFINITY)
return;
NBestState state = new NBestState(score,pointer,n,k);
mPriorityQueue.offer(state);
}
public ScoredTagging bufferNext() {
NBestState resultState = mPriorityQueue.poll();
if (resultState == null) return null;
// this needs to be a while loop walking back and
// taking alternatives at each state
int n = resultState.mN-1;
int k = resultState.mK;
ForwardPointer fwdPointer = resultState.mForwardPointer;
while (n >= 0) {
addAlternatives(n,k,fwdPointer);
int kMinus1 = mBackPointers[n][k];
double fwdScore = mTransitionScores[n][kMinus1][k];
if (fwdPointer != null)
fwdScore += fwdPointer.mScore;
fwdPointer = new ForwardPointer(k,fwdPointer,fwdScore);
k = kMinus1;
--n;
}
ScoredTagging scoredTagging = toScoredTagging(resultState);
return scoredTagging;
}
void addAlternatives(int n, int k, ForwardPointer fwdPointer) {
int numTags = mTagList.size();
for (int kMinus1 = 0; kMinus1 < numTags; ++kMinus1) {
if (kMinus1 == mBackPointers[n][k]) continue;
double score = mViterbiScores[n][kMinus1];
double fwdScore = mTransitionScores[n][kMinus1][k];
if (fwdPointer != null)
fwdScore += fwdPointer.mScore;
ForwardPointer pointer
= new ForwardPointer(k,fwdPointer,fwdScore);
offer(score,pointer,n,kMinus1);
}
}
public ScoredTagging toScoredTagging(NBestState state) {
List tags = new ArrayList(mTokens.size());
int k = state.mK;
tags.add(mTagList.get(k)); // could move after reverse
for (int n = state.mN; n > 0; --n) {
k = mBackPointers[n-1][k];
tags.add(mTagList.get(k));
}
Collections.reverse(tags);
for (ForwardPointer pointer = state.mForwardPointer;
pointer != null;
pointer = pointer.mPointer) {
tags.add(mTagList.get(pointer.mK));
}
return new ScoredTagging(mTokens,tags,state.score() -mLogZ);
}
}
// cut and paste from classify.LogisticRegressionClassifier
static final String INTERCEPT_FEATURE_NAME = "*&^INTERCEPT%$^&**";
static final double[][] EMPTY_DOUBLE_2D_ARRAY = new double[0][];
static final double[][][] EMPTY_DOUBLE_3D_ARRAY = new double[0][][];
static boolean[] legalStarts(int[][] tagIdss, int numTags) {
boolean[] legalStarts = new boolean[numTags];
for (int[] tagIds : tagIdss)
if (tagIds.length > 0)
legalStarts[tagIds[0]] = true;
return legalStarts;
}
static boolean[] legalEnds(int[][] tagIdss, int numTags) {
boolean[] legalEnds = new boolean[numTags];
for (int[] tagIds : tagIdss)
if (tagIds.length > 0)
legalEnds[tagIds[tagIds.length-1]] = true;
return legalEnds;
}
static boolean[][] legalTransitions(int[][] tagIdss, int numTags) {
boolean[][] legalTransitions = new boolean[numTags][numTags];
for (int[] tagIds : tagIdss) {
for (int i = 1; i < tagIds.length; ++i)
legalTransitions[tagIds[i-1]][tagIds[i]] = true;
}
return legalTransitions;
}
static boolean[] trueArray(int m) {
boolean[] result = new boolean[m];
Arrays.fill(result,true);
return result;
}
static boolean[][] trueArray(int m, int n) {
boolean[][] result = new boolean[m][n];
for (boolean[] row : result)
Arrays.fill(row,true);
return result;
}
static class Serializer extends AbstractExternalizable {
static final long serialVersionUID = -4140295941325870709L;
final ChainCrf mCrf;
public Serializer(ChainCrf crf) {
mCrf = crf;
}
public Serializer() {
this(null);
}
public void writeExternal(ObjectOutput out)
throws IOException {
int numTags = mCrf.mTagList.size();
out.writeInt(numTags);
for (String tag : mCrf.mTagList)
out.writeUTF(tag);
for (int i = 0; i < numTags; ++i)
out.writeBoolean(mCrf.mLegalTagStarts[i]);
for (int i = 0; i < numTags; ++i)
out.writeBoolean(mCrf.mLegalTagEnds[i]);
for (int i = 0; i < numTags; ++i)
for (int j = 0; j < numTags; ++j)
out.writeBoolean(mCrf.mLegalTagTransitions[i][j]);
for (Vector v : mCrf.mCoefficients)
out.writeObject(v);
out.writeObject(mCrf.mFeatureSymbolTable);
out.writeObject(mCrf.mFeatureExtractor);
out.writeBoolean(mCrf.mAddInterceptFeature);
}
public Object read(ObjectInput in)
throws ClassNotFoundException, IOException {
int numTags = in.readInt();
String[] tags = new String[numTags];
for (int i = 0; i < tags.length; ++i)
tags[i] = in.readUTF();
boolean[] legalTagStarts = new boolean[numTags];
for (int i = 0; i < numTags; ++i)
legalTagStarts[i] = in.readBoolean();
boolean[] legalTagEnds = new boolean[numTags];
for (int i = 0; i < numTags; ++i)
legalTagEnds[i] = in.readBoolean();
boolean[][] legalTagTransitions = new boolean[numTags][numTags];
for (int i = 0; i < numTags; ++i)
for (int j = 0; j < numTags; ++j)
legalTagTransitions[i][j] = in.readBoolean();
Vector[] coefficients = new Vector[numTags];
for (int i = 0; i < tags.length; ++i)
coefficients[i] = (Vector) in.readObject();
@SuppressWarnings("unchecked")
SymbolTable featureSymbolTable
= (SymbolTable) in.readObject();
@SuppressWarnings("unchecked")
ChainCrfFeatureExtractor featureExtractor
= (ChainCrfFeatureExtractor) in.readObject();
boolean addInterceptFeature = in.readBoolean();
return new ChainCrf(tags,
legalTagStarts,
legalTagEnds,
legalTagTransitions,
coefficients,
featureSymbolTable,
featureExtractor,
addInterceptFeature);
}
}
// aka int linked list
static class ForwardPointer {
final int mK;
final ForwardPointer mPointer;
final double mScore;
ForwardPointer(int k, ForwardPointer pointer, double score) {
mK = k;
mPointer = pointer;
mScore = score;
}
}
// score is path score following backpointers
// and forward pointers
static class NBestState implements Scored {
final double mScore;
final ForwardPointer mForwardPointer;
final int mN;
final int mK;
NBestState(double score,
ForwardPointer forwardPointer,
int n,
int k) {
mScore = score;
mForwardPointer = forwardPointer;
mN = n;
mK = k;
}
public double score() {
return (mForwardPointer != null)
? mScore + mForwardPointer.mScore
: mScore;
}
}
/**
* Return the CRF estimated using stochastic gradient descent with
* the specified prior from the specified corpus of taggings of
* type {@code F} pruned to the specified minimum feature count,
* using the specified feature extractor, automatically adding an
* intercept feature if the flag is {@code true}, allow unseen tag
* transitions as specified, using the specified training
* parameters for annealing, measuring convergence, and reporting
* the incremental results to the specified reporter.
*
* Reporting at the info level provides parameter and epoch
* level. At the debug level, it reports epoch-by-epoch
* likelihoods.
*
* @param corpus Corpus from which to estimate.
* @param featureExtractor Feature extractor for the CRF.
* @param addInterceptFeature Set to {@code true} if an intercept
* feature with index 0 is automatically added to all feature
* vectors with value 1.0.
* @param minFeatureCount Minimum number of instances of a feature
* to keep it.
* @param cacheFeatureVectors Flag indicating whether or not to
* keep the computed feature vectors in memory.
* @param allowUnseenTransitions Flag indicating whether to allow
* tags to start a tagging, end a tagging, or follow another tag
* if there was not an example of that in the corpus.
* @param prior Prior for coefficients to use during estimation.
* @param annealingSchedule Schedule for annealing the learning
* rate during gradient descent.
* @param minImprovement Minimum relative improvement objective
* (log likelihood plus log prior) computed as a 10-epoch rolling
* average to signal convergence.
* @param minEpochs Minimum number of epochs for which to run
* gradient descent estimation.
* @param maxEpochs Maximum number of epochs for which to run
* gradient descent estimation.
* @param reporter Reporter to which results are written, or
* {@code null} for no reporting of intermediate results.
*/
public static ChainCrf
estimate(Corpus>> corpus,
ChainCrfFeatureExtractor featureExtractor,
boolean addInterceptFeature,
int minFeatureCount,
boolean cacheFeatureVectors,
boolean allowUnseenTransitions,
RegressionPrior prior,
int priorBlockSize,
AnnealingSchedule annealingSchedule,
double minImprovement,
int minEpochs,
int maxEpochs,
Reporter reporter)
throws IOException {
if (reporter == null)
reporter = Reporters.silent();
reporter.info("ChainCrf.estimate Parameters");
reporter.info("featureExtractor=" + featureExtractor);
reporter.info("addInterceptFeature=" + addInterceptFeature);
reporter.info("minFeatureCount=" + minFeatureCount);
reporter.info("cacheFeatureVectors=" + cacheFeatureVectors);
reporter.info("allowUnseenTransitions=" + allowUnseenTransitions);
reporter.info("prior=" + prior);
reporter.info("annealingSchedule=" + annealingSchedule);
reporter.info("minImprovement=" + minImprovement);
reporter.info("minEpochs=" + minEpochs);
reporter.info("maxEpochs=" + maxEpochs);
reporter.info("priorBlockSize=" + priorBlockSize);
reporter.info("Computing corpus tokens and features");
List> tokenss = corpusTokens(corpus);
String[][] tagss = corpusTags(corpus);
int numTrainingInstances = tagss.length;
int longestInput = longestInput(tagss);
long numTrainingTokens = 0L;
for (String[] tags : tagss)
numTrainingTokens += tags.length;
int[][] tagIdss = new int[tagss.length][];
MapSymbolTable tagSymbolTable
= tagSymbolTable(tagss,tagIdss);
MapSymbolTable featureSymbolTable
= featureSymbolTable(tagss,tokenss,
addInterceptFeature,
featureExtractor,
minFeatureCount);
int numTags = tagSymbolTable.numSymbols();
String[] allTags = new String[numTags];
for (int n = 0; n < numTags; ++n)
allTags[n] = tagSymbolTable.idToSymbol(n);
boolean[] legalTagStarts
= allowUnseenTransitions
? trueArray(numTags)
: legalStarts(tagIdss,numTags);
boolean[] legalTagEnds
= allowUnseenTransitions
? trueArray(numTags)
: legalEnds(tagIdss,numTags);
boolean[][] legalTagTransitions
= allowUnseenTransitions
? trueArray(numTags,numTags)
: legalTransitions(tagIdss,numTags);
int numDimensions = featureSymbolTable.numSymbols();
DenseVector[] weightVectors = new DenseVector[numTags];
for (int i = 0; i < weightVectors.length; ++i)
weightVectors[i] = new DenseVector(numDimensions);
reporter.info("Corpus Statistics");
reporter.info("Num Training Instances=" + numTrainingInstances);
reporter.info("Num Training Tokens=" + numTrainingTokens);
reporter.info("Num Dimensions After Pruning=" + numDimensions);
reporter.info("Tags=" + tagSymbolTable);
ChainCrf crf = new ChainCrf(allTags,
legalTagStarts,
legalTagEnds,
legalTagTransitions,
weightVectors,
featureSymbolTable,
featureExtractor,
addInterceptFeature);
FeatureVectors[] featureVectorsCache
= cacheFeatureVectors
? new FeatureVectors[numTrainingInstances]
: null;
if (cacheFeatureVectors) {
reporter.info("Caching Feature Vectors");
for (int j = 0; j < numTrainingInstances; ++j)
featureVectorsCache[j] = crf.features(tokenss.get(j));
}
double lastLog2LikelihoodAndPrior = -(Double.MAX_VALUE / 2.0);
double rollingAverageRelativeDiff = 1.0; // arbitrary starting point
double bestLog2LikelihoodAndPrior = Double.NEGATIVE_INFINITY;
long cumFeatureExtractionMs = 0L;
long cumForwardBackwardMs = 0L;
long cumUpdateMs = 0L;
long cumLossMs = 0L;
long cumPriorUpdateMs = 0L;
for (int epoch = 0; epoch < maxEpochs; ++epoch) {
int instancesSinceLastPriorUpdate = 0;
double learningRate = annealingSchedule.learningRate(epoch);
double learningRatePerTrainingInstance = learningRate / numTrainingInstances;
for (int j = 0; j < numTrainingInstances; ++j) {
int[] tagIds = tagIdss[j];
List tokens = tokenss.get(j);
int numTokens = tokens.size();
if (numTokens < 1) continue;
long startMs = System.currentTimeMillis();
FeatureVectors features
= cacheFeatureVectors
? featureVectorsCache[j]
: crf.features(tokens);
long featsMs = System.currentTimeMillis();
cumFeatureExtractionMs += (featsMs - startMs);
TagLattice lattice
= crf.forwardBackward(tokens,features);
long fwdBkMs = System.currentTimeMillis();
cumForwardBackwardMs += (fwdBkMs - featsMs);
// coeffs += learnRate * (true - expectation)
for (int nTo = 0; nTo < numTokens; ++nTo) {
weightVectors[tagIds[nTo]].increment(learningRate,
features.mNodeFeatureVectors[nTo]);
}
for (int nTo = 1; nTo < numTokens; ++nTo) {
weightVectors[tagIds[nTo]].increment(learningRate,
features.mEdgeFeatureVectorss[nTo-1][tagIds[nTo-1]]);
}
// Coeffs -= learnRate * expectation (step 2, coeffs += learnRate * (true - expectation)
for (int nTo = 0; nTo < numTokens; ++nTo) {
for (int kTo = 0; kTo < numTags; ++kTo) {
double logP = lattice.logProbability(nTo,kTo);
if (logP < -400.0) continue; // will underflow to 0.0 or close enough
double p = Math.exp(logP);
weightVectors[kTo].increment(-p*learningRate,
features.mNodeFeatureVectors[nTo]);
}
}
for (int nTo = 1; nTo < numTokens; ++nTo) {
for (int kFrom = 0; kFrom < numTags; ++kFrom) {
for (int kTo = 0; kTo < numTags; ++kTo) {
double logP = lattice.logProbability(nTo,kFrom,kTo);
if (logP < -400) continue;
double p = Math.exp(logP);
weightVectors[kTo].increment(-p*learningRate,
features.mEdgeFeatureVectorss[nTo-1][kFrom]);
}
}
}
long updateMs = System.currentTimeMillis();
cumUpdateMs += (updateMs-fwdBkMs);
// put this on a blocked basis for efficiency
if ((++instancesSinceLastPriorUpdate) == priorBlockSize) {
adjustWeightsWithPrior(weightVectors,prior,
instancesSinceLastPriorUpdate * learningRatePerTrainingInstance);
instancesSinceLastPriorUpdate = 0;
}
long priorMs = System.currentTimeMillis();
cumPriorUpdateMs += (priorMs - updateMs);
}
long finalPriorStartMs = System.currentTimeMillis();
adjustWeightsWithPrior(weightVectors,prior,
instancesSinceLastPriorUpdate * learningRatePerTrainingInstance);
long finalPriorEndMs = System.currentTimeMillis();
cumPriorUpdateMs += (finalPriorEndMs - finalPriorStartMs);
long lossStartMs = System.currentTimeMillis();
// loss function
double log2Likelihood = 0.0;
for (int j = 0; j < numTrainingInstances; ++j) {
// don't really need lattice of features or backward part of lattice
if (tokenss.get(j).size() < 1) continue;
FeatureVectors features
= cacheFeatureVectors
? featureVectorsCache[j]
: crf.features(tokenss.get(j));
TagLattice lattice = crf.forwardBackward(tokenss.get(j),features);
log2Likelihood += lattice.logProbability(0,tagIdss[j]);
}
double log2Prior = prior == null ? 0.0 : prior.log2Prior(weightVectors);
double log2LikelihoodAndPrior = log2Likelihood + log2Prior;
double relativeDiff = com.aliasi.util.Math
.relativeAbsoluteDifference(lastLog2LikelihoodAndPrior,log2LikelihoodAndPrior);
rollingAverageRelativeDiff = (9.0 * rollingAverageRelativeDiff + relativeDiff)/10.0;
lastLog2LikelihoodAndPrior = log2LikelihoodAndPrior;
if (log2LikelihoodAndPrior > bestLog2LikelihoodAndPrior)
bestLog2LikelihoodAndPrior = log2LikelihoodAndPrior;
long lossMs = System.currentTimeMillis();
cumLossMs += (lossMs - lossStartMs);
if (reporter.isDebugEnabled()) {
Formatter formatter = null;
try {
formatter = new Formatter(Locale.ENGLISH);
formatter.format("epoch=%5d lr=%11.9f ll=%11.4f lp=%11.4f llp=%11.4f llp*=%11.4f",
epoch,
learningRate,
log2Likelihood,
log2Prior,
log2LikelihoodAndPrior,
bestLog2LikelihoodAndPrior);
reporter.debug(formatter.toString());
} catch (IllegalFormatException e) {
reporter.warn("Illegal format in Logistic Regression");
} finally {
if (formatter != null)
formatter.close();
}
}
if (rollingAverageRelativeDiff < minImprovement) {
reporter.info("Converged with rollingAverageRelativeDiff="
+ rollingAverageRelativeDiff);
break; // goes to "return regression;"
}
}
reporter.info("Feat Extraction Time=" + Strings.msToString(cumFeatureExtractionMs));
reporter.info("Forward Backward Time=" + Strings.msToString(cumForwardBackwardMs));
reporter.info("Update Time=" + Strings.msToString(cumUpdateMs));
reporter.info("Prior Update Time=" + Strings.msToString(cumPriorUpdateMs));
reporter.info("Loss Time=" + Strings.msToString(cumLossMs));
return crf;
}
// cut and pasted from stats.LogisticRegression.adjustWeightsWithPriorDense()
static void adjustWeightsWithPrior(DenseVector[] weightVectors,
RegressionPrior prior,
double learningRateDividedByNumTrainingInstances) {
if (prior.isUniform()) return;
for (DenseVector weightVectorsK : weightVectors) {
for (int dim = 0; dim < weightVectorsK.numDimensions(); ++dim) {
double weightVectorsKDim = weightVectorsK.value(dim);
double priorMode = prior.mode(dim);
if (weightVectorsKDim == priorMode)
continue;
double priorGradient = prior.gradient(weightVectorsKDim,dim);
double delta = priorGradient * learningRateDividedByNumTrainingInstances;
//clip normalization to 0
double newVal = weightVectorsKDim > priorMode
? Math.max(priorMode, weightVectorsKDim - delta)
: Math.min(priorMode, weightVectorsKDim - delta);
weightVectorsK.setValue(dim, newVal);
}
}
}
static MapSymbolTable tagSymbolTable(String[][] tagss, int[][] tagIdss) {
MapSymbolTable tagSymbolTable = new MapSymbolTable();
for (int j = 0; j < tagss.length; ++j) {
tagIdss[j] = new int[tagss[j].length];
for (int n = 0; n < tagIdss[j].length; ++n) {
tagIdss[j][n] = tagSymbolTable.getOrAddSymbol(tagss[j][n]);
}
}
return tagSymbolTable;
}
static MapSymbolTable featureSymbolTable(String[][] tagss,
List> tokenss,
boolean addInterceptFeature,
ChainCrfFeatureExtractor featureExtractor,
int minFeatureCount) {
ObjectToCounterMap featureCounter
= new ObjectToCounterMap();
for (int j = 0; j < tagss.length; ++j) {
String[] tags = tagss[j];
List tagList = Arrays.asList(tags);
List tokens = tokenss.get(j);
ChainCrfFeatures features = featureExtractor.extract(tokens,tagList);
// DIRECT REFACTOR; BUGGY?
for (int n = 0; n < tags.length; ++n) {
for (String feature : features.nodeFeatures(n).keySet())
featureCounter.increment(feature);
}
for (int k = 1; k < tags.length; ++k) {
// Edge edge = new Edge(tokens,k,tags[k-1]);
for (String feature : features.edgeFeatures(k,k-1).keySet())
featureCounter.increment(feature);
}
// SHOULD BE?
// for (int n = 0; n < tokens.size(); ++n)
// for (String feature : features.nodeFeatures(n).keySet())
// featureCounter.increment(feature);
// edge features start at 1
// for (int n = 1; n < tokens.size(); ++n)
// for (int k = 0; k < tags.length; ++k)
// for (String feature : features.edgeFeatures(n,k).keySet())
// featureCounter.increment(feature);
}
featureCounter.prune(minFeatureCount);
MapSymbolTable featureSymbolTable = new MapSymbolTable();
// first add intercept in position 0 if exists
if (addInterceptFeature)
featureSymbolTable.getOrAddSymbol(INTERCEPT_FEATURE_NAME);
for (String feature : featureCounter.keySet())
featureSymbolTable.getOrAddSymbol(feature);
return featureSymbolTable;
}
static List> corpusTokens(Corpus>> corpus)
throws IOException {
final List> corpusTokenList = new ArrayList>();
corpus.visitTrain(new ObjectHandler>() {
public void handle(Tagging tagging) {
corpusTokenList.add(tagging.tokens());
}
});
return corpusTokenList; // could be a bit too large by auto-allocation
}
static String[][] corpusTags(Corpus>> corpus)
throws IOException {
final List corpusTagList = new ArrayList(1024);
corpus.visitTrain(new ObjectHandler>() {
public void handle(Tagging tagging) {
corpusTagList.add(tagging.tags().toArray(Strings.EMPTY_STRING_ARRAY));
}
});
return corpusTagList.toArray(Strings.EMPTY_STRING_2D_ARRAY);
}
// cut and paste from stats.LogisticRegression
static DenseVector[] copy(DenseVector[] xs) {
DenseVector[] result = new DenseVector[xs.length];
for (int k = 0; k < xs.length; ++k)
result[k] = new DenseVector(xs[k]);
return result;
}
static int longestInput(String[][] tagss) {
int longest = 0;
for (String[] tags : tagss)
if (tags.length > longest)
longest = tags.length;
return longest;
}
static class FeatureVectors {
// mNodeFeatureVectors[nTo:N]
final Vector[] mNodeFeatureVectors;
// mEdgeFeatureVectorss[nFrom:(N-1)][kFrom:K]
final Vector[][] mEdgeFeatureVectorss; // length N-1, indexed by nFrom
FeatureVectors(Vector[] nodeFeatureVectors,
Vector[][] edgeFeatureVectorss) {
mNodeFeatureVectors = nodeFeatureVectors;
mEdgeFeatureVectorss = edgeFeatureVectorss;
}
}
}