package LBJ2.classify;
import LBJ2.learn.Lexicon;
import LBJ2.util.ByteString;
import LBJ2.util.ExceptionlessInputStream;
import LBJ2.util.ExceptionlessOutputStream;
/**
* A referring discrete feature is one that has its own identifier, but whose
* value comes from a separate feature that it refers to.
*
* @author Nick Rizzolo
**/
public class DiscreteReferringStringFeature extends DiscreteReferrer
{
/**
* The <code>identifier</code> string distinguishes this
* <code>Feature</code> from other <code>Feature</code>s.
**/
protected String identifier;
/**
* For internal use only.
*
* @see Feature#readFeature(ExceptionlessInputStream)
**/
protected DiscreteReferringStringFeature() { }
/**
* Sets both the identifier and the referent.
*
* @param c The classifier that produced this feature.
* @param i The new referring feature's identifier.
* @param r The discrete feature referred to by this new feature.
**/
public DiscreteReferringStringFeature(Classifier c, String i,
DiscreteFeature r) {
this(c.containingPackage, c.name, i, r, r.getValueIndex(),
r.totalValues());
}
/**
* Sets both the identifier and the referent.
*
* @param c The classifier that produced this feature.
* @param i The new referring feature's identifier.
* @param r The discrete feature referred to by this new feature.
* @param av The allowable values of the classifier that produced
* <code>r</code>.
**/
public DiscreteReferringStringFeature(Classifier c, String i,
DiscreteFeature r, String[] av) {
super(c, r, av);
identifier = i;
}
/**
* Constructs a new referring feature.
*
* @param p The new discrete feature's package.
* @param c The name of the classifier that produced this feature.
* @param i The new discrete feature's identifier.
* @param r The discrete feature referred to by this new feature.
* @param vi The index corresponding to the value.
* @param t The total allowable values for this feature.
**/
public DiscreteReferringStringFeature(String p, String c, String i,
DiscreteFeature r, short vi, short t)
{
super(p, c, r, vi, t);
identifier = i;
}
/**
* Determines if this feature contains a string identifier field.
*
* @return <code>true</code> iff this feature contains a string identifier
* field.
**/
public boolean hasStringIdentifier() { return true; }
/**
* Retrieves this feature's identifier as a string.
*
* @return This feature's identifier as a string.
**/
public String getStringIdentifier() { return identifier; }
/**
* Retrieves this feature's identifier as a byte string.
*
* @return This feature's identifier as a byte string.
**/
public ByteString getByteStringIdentifier() {
return new ByteString(identifier);
}
/**
* Return the feature that should be used to index this feature into a
* lexicon. If it is a binary feature, we return the feature with an empty
* value so that the feature will be mapped to the same weight whether it
* is active or not. If the feature can take multiple values, then simply
* return the feature object as-is.
*
* @param lexicon The lexicon into which this feature will be indexed.
* @param training Whether or not the learner is currently training.
* @param label The label of the example containing this feature, or -1
* if we aren't doing per class feature counting.
* @return A feature object appropriate for use as the key of a map.
**/
public Feature getFeatureKey(Lexicon lexicon, boolean training, int label) {
DiscreteFeature f =
(DiscreteFeature) referent.getFeatureKey(lexicon, training, label);
if (training) f = (DiscreteFeature) lexicon.getChildFeature(f, label);
else if (f == referent) return this;
return
new DiscreteReferringStringFeature(
containingPackage, generatingClassifier, identifier, f,
valueIndex, totalValues);
}
/**
* Returns a {@link RealPrimitiveFeature} whose
* {@link RealPrimitiveFeature#value value} field is set to the strength of
* the current feature, and whose {@link #identifier} field contains all
* the information necessary to distinguish this feature from other
* features.
**/
public RealFeature makeReal() {
return
new RealReferringStringFeature(
containingPackage, generatingClassifier, identifier,
referent.makeReal());
}
/**
* Returns the strength of this feature if it were to be placed in a
* mathematical vector space.
**/
public double getStrength() { return referent.getStrength(); }
/**
* Returns a new feature object that's identical to this feature except its
* strength is given by <code>s</code>.
*
* @param s The strength of the new feature.
* @return A new feature object as above, or <code>null</code> if this
* feature cannot take the specified strength.
**/
public Feature withStrength(double s) {
DiscreteFeature f = (DiscreteFeature) referent.withStrength(s);
if (f == null) return null;
return
new DiscreteReferringStringFeature(
containingPackage, generatingClassifier, identifier, f,
(short) Math.round(f.getStrength()), totalValues);
}
/**
* Returns a feature object in which any strings that are being used to
* represent an identifier or value have been encoded in byte strings.
*
* @param e The encoding to use.
* @return A feature object as above; possible this object.
**/
public Feature encode(String e) {
DiscreteFeature newReferent = (DiscreteFeature) referent.encode(e);
if (referent == newReferent && (e == null || e == "String")) return this;
ByteString id =
identifier.length() == 0 ? ByteString.emptyString
: new ByteString(identifier, e);
return
new DiscreteReferringFeature(
containingPackage, generatingClassifier, id, newReferent,
valueIndex, totalValues);
}
/**
* The hash code of a <code>DiscreteReferringStringFeature</code> is the
* sum of the hash codes of its containing package, identifier, and the
* referent feature.
*
* @return The hash code of this feature.
**/
public int hashCode() {
return 17 * super.hashCode() + identifier.hashCode();
}
/**
* Two <code>DiscreteReferringStringFeature</code>s are equivalent when
* their containing packages, identifiers, and referent features are
* equivalent.
*
* @param o The object with which to compare this feature.
* @return <code>true</code> iff the parameter is an equivalent feature.
**/
public boolean equals(Object o) {
return
super.equals(o)
&& (o instanceof DiscreteReferringStringFeature
? identifier.equals(((DiscreteReferringStringFeature) o).identifier)
: identifier.equals(((DiscreteReferringFeature) o).identifier))
&& referent.equals(((DiscreteReferrer) o).referent);
}
/**
* Some features are functionally equivalent, differing only in the
* encoding of their values; this method will return <code>true</code> iff
* the class of this feature and <code>f</code> are different, but they
* differ only because they encode their values differently. This method
* does not compare the values themselves, however.
*
* @param f Another feature.
* @return See above.
**/
public boolean classEquivalent(Feature f) {
return f instanceof DiscreteReferringFeature;
}
/**
* Compares only the run-time types, packages, classifier names, and
* identifiers of the features.
*
* @param o An object to compare with.
* @return Integers appropriate for sorting features first by package, then
* by classifier name, and then by identifier.
**/
public int compareNameStrings(Object o) {
int d = super.compareNameStrings(o);
if (d != 0) return d;
return
identifier.compareTo(((DiscreteReferringStringFeature) o).identifier);
}
/**
* Writes a string representation of this <code>Feature</code>'s package,
* generating classifier, and identifier information to the specified
* buffer.
*
* @param buffer The buffer to write to.
**/
public void writeNameString(StringBuffer buffer) {
super.writeNameString(buffer);
buffer.append(":");
buffer.append(identifier);
}
/**
* Writes a complete binary representation of the feature.
*
* @param out The output stream.
**/
public void write(ExceptionlessOutputStream out) {
super.write(out);
out.writeString(identifier);
}
/**
* Reads the representation of a feaeture with this object's run-time type
* from the given stream, overwriting the data in this object.
*
* @param in The input stream.
**/
public void read(ExceptionlessInputStream in) {
super.read(in);
identifier = in.readString();
}
/**
* Writes a binary representation of the feature intended for use by a
* lexicon, omitting redundant information when possible.
*
* @param out The output stream.
* @param lex The lexicon out of which this feature is being written.
* @param c The fully qualified name of the assumed class. The runtime
* class of this feature won't be written if it's equivalent to
* <code>c</code>.
* @param p The assumed package string. This feature's package string
* won't be written if it's equivalent to <code>p</code>.
* @param g The assumed classifier name string. This feature's
* classifier name string won't be written if it's equivalent
* to <code>g</code>.
* @param si The assumed identifier as a string. If this feature has a
* string identifier, it won't be written if it's equivalent to
* <code>si</code>.
* @param bi The assumed identifier as a byte string. If this feature
* has a byte string identifier, it won't be written if it's
* equivalent to <code>bi</code>.
* @return The name of the runtime type of this feature.
**/
public String lexWrite(ExceptionlessOutputStream out, Lexicon lex, String c,
String p, String g, String si, ByteString bi) {
String result = super.lexWrite(out, lex, c, p, g, si, bi);
out.writeString(identifier.equals(si) ? null : identifier);
return result;
}
/**
* Reads the representation of a feature with this object's run-time type
* as stored by a lexicon, overwriting the data in this object.
*
* <p> This method is appropriate for reading features as written by
* {@link #lexWrite(ExceptionlessOutputStream,Lexicon,String,String,String,String,ByteString)}.
*
* @param in The input stream.
* @param lex The lexicon we are reading in to.
* @param p The assumed package string. If no package name is given in
* the input stream, the instantiated feature is given this
* package.
* @param g The assumed classifier name string. If no classifier name
* is given in the input stream, the instantiated feature is
* given this classifier name.
* @param si The assumed identifier as a string. If the feature being
* read has a string identifier field and no identifier is
* given in the input stream, the feature is given this
* identifier.
* @param bi The assumed identifier as a byte string. If the feature
* being read has a byte string identifier field and no
* identifier is given in the input stream, the feature is
* given this identifier.
**/
public void lexRead(ExceptionlessInputStream in, Lexicon lex, String p,
String g, String si, ByteString bi) {
super.lexRead(in, lex, p, g, si, bi);
identifier = in.readString();
if (identifier == null) identifier = si;
}
}