/**
* If this tree contains max-marginals, recover the best parse subtree for a given symbol with the
* specified span.
*/
public CfgParseTree getBestParseTreeWithSpan(Object root, int spanStart, int spanEnd) {
Preconditions.checkState(!sumProduct);
Assignment rootAssignment = parentVar.outcomeArrayToAssignment(root);
int rootNonterminalNum = parentVar.assignmentToIntArray(rootAssignment)[0];
double prob =
insideChart[spanStart][spanEnd][rootNonterminalNum]
* outsideChart[spanStart][spanEnd][rootNonterminalNum];
if (prob == 0.0) {
return null;
}
int splitInd = splitBackpointers[spanStart][spanEnd][rootNonterminalNum];
if (splitInd < 0) {
long terminalKey = backpointers[spanStart][spanEnd][rootNonterminalNum];
int positiveSplitInd = (-1 * splitInd) - 1;
int terminalSpanStart = positiveSplitInd / numTerminals;
int terminalSpanEnd = positiveSplitInd % numTerminals;
// This is a really sucky way to transform the keys back to objects.
VariableNumMap vars = parentVar.union(ruleTypeVar);
int[] dimKey = TableFactor.zero(vars).getWeights().keyNumToDimKey(terminalKey);
Assignment a = vars.intArrayToAssignment(dimKey);
Object ruleType = a.getValue(ruleTypeVar.getOnlyVariableNum());
List<Object> terminalList = Lists.newArrayList();
terminalList.addAll(terminals.subList(terminalSpanStart, terminalSpanEnd + 1));
return new CfgParseTree(root, ruleType, terminalList, prob, spanStart, spanEnd);
} else {
long binaryRuleKey = backpointers[spanStart][spanEnd][rootNonterminalNum];
int[] binaryRuleComponents =
binaryRuleDistribution.coerceToDiscrete().getWeights().keyNumToDimKey(binaryRuleKey);
Assignment best = binaryRuleDistribution.getVars().intArrayToAssignment(binaryRuleComponents);
Object leftRoot = best.getValue(leftVar.getOnlyVariableNum());
Object rightRoot = best.getValue(rightVar.getOnlyVariableNum());
Object ruleType = best.getValue(ruleTypeVar.getOnlyVariableNum());
Preconditions.checkArgument(
spanStart + splitInd != spanEnd,
"CFG parse decoding error: %s %s %s",
spanStart,
spanEnd,
splitInd);
CfgParseTree leftTree = getBestParseTreeWithSpan(leftRoot, spanStart, spanStart + splitInd);
CfgParseTree rightTree =
getBestParseTreeWithSpan(rightRoot, spanStart + splitInd + 1, spanEnd);
Preconditions.checkState(leftTree != null);
Preconditions.checkState(rightTree != null);
return new CfgParseTree(root, ruleType, leftTree, rightTree, prob);
}
}
@Override
public double getUnnormalizedLogProbability(Assignment assignment) {
Preconditions.checkArgument(assignment.containsAll(getVars().getVariableNumsArray()));
Tensor inputFeatureVector =
(Tensor) assignment.getValue(getInputVariable().getOnlyVariableNum());
if (conditionalVars.size() == 0) {
// No normalization for any conditioned-on variables. This case
// allows a more efficient implementation than the default
// in ClassifierFactor.
VariableNumMap outputVars = getOutputVariables();
Tensor outputTensor =
SparseTensor.singleElement(
outputVars.getVariableNumsArray(),
outputVars.getVariableSizes(),
outputVars.assignmentToIntArray(assignment),
1.0);
Tensor featureIndicator = outputTensor.outerProduct(inputFeatureVector);
return logWeights.innerProduct(featureIndicator).getByDimKey();
} else {
// Default to looking up the answer in the output log probabilities
int[] outputIndexes = getOutputVariables().assignmentToIntArray(assignment);
Tensor logProbs = getOutputLogProbTensor(inputFeatureVector);
return logProbs.getByDimKey(outputIndexes);
}
}
