/**
* 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);
}
}
/**
* Create a parse chart with the specified number of terminal symbols.
*
* <p>If "sumProduct" is true, then updates for the same symbol add (i.e., the ParseChart computes
* marginals). Otherwise, updates use the maximum probability, meaning ParseChart computes
* max-marginals.
*/
public CfgParseChart(
List<?> terminals,
VariableNumMap parent,
VariableNumMap left,
VariableNumMap right,
VariableNumMap terminal,
VariableNumMap ruleTypeVar,
Factor binaryRuleDistribution,
boolean sumProduct) {
this.terminals = terminals;
this.parentVar = parent;
this.leftVar = left;
this.rightVar = right;
this.ruleTypeVar = ruleTypeVar;
this.terminalVar = terminal;
this.sumProduct = sumProduct;
this.numTerminals = terminals.size();
this.numNonterminals = parentVar.getDiscreteVariables().get(0).numValues();
insideChart = new double[numTerminals][numTerminals][numNonterminals];
outsideChart = new double[numTerminals][numTerminals][numNonterminals];
this.binaryRuleDistribution = binaryRuleDistribution;
binaryRuleExpectations =
new double[binaryRuleDistribution.coerceToDiscrete().getWeights().getValues().length];
terminalRuleExpectations =
TableFactor.zero(VariableNumMap.unionAll(parentVar, terminalVar, ruleTypeVar));
insideCalculated = false;
outsideCalculated = false;
partitionFunction = 0.0;
if (!sumProduct) {
backpointers = new long[numTerminals][numTerminals][numNonterminals];
splitBackpointers = new int[numTerminals][numTerminals][numNonterminals];
} else {
backpointers = null;
splitBackpointers = null;
}
}
