ANTLR 4.13.1 · org.antlr.v4.runtime.atn.ATNSimulator

Field Summary

Modifier and Type	Field and Description
public final ATN	atn
public static final DFAState	ERROR Must distinguish between missing edge and edge we know leads nowhere
protected final PredictionContextCache	sharedContextCache The context cache maps all PredictionContext objects that are equals() to a single cached copy.

Constructor Summary

Access	Constructor and Description
public	ATNSimulator(ATN atn, PredictionContextCache sharedContextCache)

Method Summary

Modifier and Type	Method and Description
public void	clearDFA() Clear the DFA cache used by the current instance.
public PredictionContext	getCachedContext(PredictionContext context)
public PredictionContextCache	getSharedContextCache()
public abstract void	reset()

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

atn	back to summary
public final ATN atn

ERROR	back to summary
public static final DFAState ERROR Must distinguish between missing edge and edge we know leads nowhere

sharedContextCache	back to summary
protected final PredictionContextCache sharedContextCache The context cache maps all PredictionContext objects that are equals() to a single cached copy. This cache is shared across all contexts in all ATNConfigs in all DFA states. We rebuild each ATNConfigSet to use only cached nodes/graphs in addDFAState(). We don't want to fill this during closure() since there are lots of contexts that pop up but are not used ever again. It also greatly slows down closure(). This cache makes a huge difference in memory and a little bit in speed. For the Java grammar on java.*, it dropped the memory requirements at the end from 25M to 16M. We don't store any of the full context graphs in the DFA because they are limited to local context only, but apparently there's a lot of repetition there as well. We optimize the config contexts before storing the config set in the DFA states by literally rebuilding them with cached subgraphs only. I tried a cache for use during closure operations, that was whacked after each adaptivePredict(). It cost a little bit more time I think and doesn't save on the overall footprint so it's not worth the complexity.

sharedContextCache

back to summary

protected final PredictionContextCache sharedContextCache

The context cache maps all PredictionContext objects that are equals() to a single cached copy. This cache is shared across all contexts in all ATNConfigs in all DFA states. We rebuild each ATNConfigSet to use only cached nodes/graphs in addDFAState(). We don't want to fill this during closure() since there are lots of contexts that pop up but are not used ever again. It also greatly slows down closure().

This cache makes a huge difference in memory and a little bit in speed. For the Java grammar on java.*, it dropped the memory requirements at the end from 25M to 16M. We don't store any of the full context graphs in the DFA because they are limited to local context only, but apparently there's a lot of repetition there as well. We optimize the config contexts before storing the config set in the DFA states by literally rebuilding them with cached subgraphs only.

I tried a cache for use during closure operations, that was whacked after each adaptivePredict(). It cost a little bit more time I think and doesn't save on the overall footprint so it's not worth the complexity.

Constructor Detail

ATNSimulator	back to summary
public ATNSimulator(ATN atn, PredictionContextCache sharedContextCache)

Method Detail

clearDFA	back to summary
public void clearDFA() Clear the DFA cache used by the current instance. Since the DFA cache may be shared by multiple ATN simulators, this method may affect the performance (but not accuracy) of other parsers which are being used concurrently. Exceptions UnsupportedOperationException: if the current instance does not support clearing the DFA. Since 4.3

clearDFA

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public void clearDFA()

Clear the DFA cache used by the current instance. Since the DFA cache may be shared by multiple ATN simulators, this method may affect the performance (but not accuracy) of other parsers which are being used concurrently.

Exceptions

UnsupportedOperationException:: if the current instance does not support clearing the DFA.

Since

4.3

getCachedContext	back to summary
public PredictionContext getCachedContext(PredictionContext context)

getSharedContextCache	back to summary
public PredictionContextCache getSharedContextCache()

reset	back to summary
public abstract void reset()