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author | Viktor Engelmann <viktor.engelmann@qt.io> | 2017-12-21 16:11:54 +0100 |
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committer | Viktor Engelmann <viktor.engelmann@qt.io> | 2018-01-04 11:21:27 +0000 |
commit | 75e9858a87307f61b478735f73c0a60c52c25eb8 (patch) | |
tree | 2f45bae9669f37c17317e1f28a57a36be26f7473 | |
parent | 4e2f2f60c2b40e462be2d75cd81f149522097734 (diff) | |
download | qtxmlpatterns-75e9858a87307f61b478735f73c0a60c52c25eb8.tar.gz |
Significantly improve memory usage in XsdStateMachine::toDFA
We now mark DFA state sets immediately when they are enqueued and
check for that mark before enqueing them. This way, we save a lot
of memory when a set has many states and is encountered often.
In the referenced bug report, there were 60000 copies of a set with
40000 entries, wasting tens of gigabytes of memory.
Task-number: QTBUG-65067
Change-Id: Iec3a04c8badfac29faefbba22c2942ed104effbb
Reviewed-by: Kari Hormi <kari.hormi@qt.io>
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>
-rw-r--r-- | src/xmlpatterns/schema/qxsdstatemachine_tpl_p.h | 16 |
1 files changed, 7 insertions, 9 deletions
diff --git a/src/xmlpatterns/schema/qxsdstatemachine_tpl_p.h b/src/xmlpatterns/schema/qxsdstatemachine_tpl_p.h index 1cb2e72..9277c1b 100644 --- a/src/xmlpatterns/schema/qxsdstatemachine_tpl_p.h +++ b/src/xmlpatterns/schema/qxsdstatemachine_tpl_p.h @@ -359,19 +359,14 @@ XsdStateMachine<TransitionType> XsdStateMachine<TransitionType>::toDFA() const QList< QSet<StateId> > workStates; // add the start state to the list of to processed state sets - workStates.append(epsilonClosure(QSet<StateId>() << startState)); + auto firstDfaState = epsilonClosure(QSet<StateId>() << startState); + workStates.append(firstDfaState); + isMarked.append(firstDfaState); while (!workStates.isEmpty()) { // as long as there are state sets to process left - // enqueue set of states const QSet<StateId> states = workStates.takeFirst(); - if (isMarked.contains(states)) // we processed this state set already - continue; - - // mark as processed - isMarked.append(states); - // select a list of all inputs that are possible for // the 'states' set QList<TransitionType> input; @@ -395,7 +390,10 @@ XsdStateMachine<TransitionType> XsdStateMachine<TransitionType>::toDFA() const dfa.addTransition(dfaBegin, input.at(i), dfaEnd); // add the 'followStates' to the list of to be processed state sets - workStates.append(followStates); + if (!isMarked.contains(followStates)) { + workStates.append(followStates); + isMarked.append(followStates); // only needs to be processed once + } } } |