@ -13,11 +13,10 @@ namespace storm {
LOG_THROW ( dtmc . getInitialStates ( ) . getNumberOfSetBits ( ) = = 1 , storm : : exceptions : : IllegalArgumentException , " Input model is required to have exactly one initial state. " ) ;
typename FlexibleSparseMatrix < ValueType > : : index_type initialStateIndex = * dtmc . getInitialStates ( ) . begin ( ) ;
storm : : storage : : BitVector relevantStates = storm : : utility : : graph : : getReachableStates ( dtmc . getTransitionMatrix ( ) , dtmc . getInitialStates ( ) , phiStates , psiStates ) ;
// Then, compute the subset of states that has a probability of 0 or 1, respectively.
std : : pair < storm : : storage : : BitVector , storm : : storage : : BitVector > statesWithProbability01 = storm : : utility : : graph : : performProb01 ( dtmc , phiStates , psiStates ) ;
storm : : storage : : BitVector statesWithProbability0 = std : : move ( st atesWithProbability01 . first ) ;
storm : : storage : : BitVector statesWithProbability1 = std : : move ( st atesWithProbability01 . second ) ;
storm : : storage : : BitVector statesWithProbability0 = statesWithProbability01 . first ;
storm : : storage : : BitVector statesWithProbability1 = statesWithProbability01 . second ;
storm : : storage : : BitVector maybeStates = ~ ( statesWithProbability0 | statesWithProbability1 ) ;
// If the initial state is known to have either probability 0 or 1, we can directly return the result.
@ -25,34 +24,76 @@ namespace storm {
return statesWithProbability0 . get ( initialStateIndex ) ? 0 : 1 ;
}
// Determine the set of states that is reachable from the initial state without jumping over a target state.
storm : : storage : : BitVector reachableStates = storm : : utility : : graph : : getReachableStates ( dtmc . getTransitionMatrix ( ) , dtmc . getInitialStates ( ) , maybeStates , statesWithProbability1 ) ;
// Otherwise, we build the submatrix that only has maybe states
// Subtract from the maybe states the set of states that is not reachable.
maybeStates & = reachableStates ;
submatrix = dtmc . getTransitionMatrix ( ) . getSubmatrix ( false , maybeStates , maybeStates ) ;
// Otherwise, we build the submatrix that only has the transitions of the maybe states.
storm : : storage : : SparseMatrix < ValueType > submatrix = dtmc . getTransitionMatrix ( ) . getSubmatrix ( false , maybeStates , maybeStates ) ;
// Then, we convert the reduced matrix to a more flexible format to be able to perform state elimination more easily.
FlexibleSparseMatrix < ValueType > flexibleMatrix = getFlexibleSparseMatrix ( dtmc . getTransitionMatrix ( ) ) ;
// Create a vector for the probabilities to go to a state with probability 1 in one step.
std : : vector < ValueType > oneStepProbabilities = dtmc . getTransitionMatrix ( ) . getConstrainedRowSumVector ( maybeStates , statesWithProbability1 ) ;
// Then, we recursively treat all SCCs.
treatScc ( dtmc , flexibleMatrix , storm : : storage : : BitVector ( dtmc . getNumberOfStates ( ) , true ) , 0 ) ;
treatScc ( dtmc , flexibleMatrix , dtmc . getInitialStates ( ) , maybeStates , statesWithProbability1 , dtmc . getBackwardTransitions ( ) , false , 0 ) ;
// Now, we return the value for the only initial state.
return flexibleMatrix . getRow ( initialStateIndex ) [ 0 ] . getValue ( ) ;
}
template < typename ValueType >
void SparseSccModelChecker < ValueType > : : treatScc ( storm : : models : : Dtmc < ValueType > const & dtmc , FlexibleSparseMatrix < ValueType > & matrix , storm : : storage : : BitVector const & scc , uint_fast64_t level ) {
if ( level < 2 ) {
void SparseSccModelChecker < ValueType > : : treatScc ( storm : : models : : Dtmc < ValueType > const & dtmc , FlexibleSparseMatrix < ValueType > & matrix , storm : : storage : : BitVector const & entryStates , storm : : storage : : BitVector const & scc , storm : : storage : : BitVector const & targetStates , storm : : storage : : SparseMatrix < ValueType > const & backwardTransitions , bool eliminateEntryStates , uint_fast64_t level ) {
if ( level < = 2 ) {
// Here, we further decompose the SCC into sub-SCCs.
storm : : storage : : StronglyConnectedComponentDecomposition < ValueType > decomposition ( dtmc , scc , true , false ) ;
// To eliminate the remaining one-state SCCs, we need to keep track of them.
storm : : storage : : BitVector remainingStates ( scc ) ;
// And then recursively treat all sub-SCCs.
for ( auto const & newScc : decomposition ) {
treatScc ( dtmc , matrix , scc , level + 1 ) ;
// If the SCC consists of just one state, we do not explore it recursively, but rather eliminate
// it directly.
if ( newScc . size ( ) = = 1 ) {
continue ;
}
// Rewrite SCC into bit vector and subtract it from the remaining states.
storm : : storage : : BitVector newSccAsBitVector ( dtmc . getNumberOfStates ( ) , newScc . begin ( ) , newScc . end ( ) ) ;
remainingStates & = ~ newSccAsBitVector ;
// Determine the set of entry states of the SCC.
storm : : storage : : BitVector entryStates ( dtmc . getNumberOfStates ( ) ) ;
for ( auto const & state : newScc ) {
for ( auto const & predecessor : backwardTransitions . getRow ( state ) ) {
if ( predecessor . getValue ( ) > storm : : utility : : constantZero < ValueType > ( ) & & ! newSccAsBitVector . get ( predecessor . getColumn ( ) ) ) {
entryStates . set ( state ) ;
}
}
}
// Recursively descend in SCC-hierarchy.
treatScc ( dtmc , matrix , entryStates , scc , targetStates , backwardTransitions , true , level + 1 ) ;
}
// If we are not supposed to eliminate the entry states, we need to take them out of the set of
// remaining states.
if ( ! eliminateEntryStates ) {
remainingStates & = ~ entryStates ;
}
// Now that we eliminated all non-trivial sub-SCCs, we need to take care of trivial sub-SCCs.
// Therefore, we need to eliminate all states.
for ( auto const & state : remainingStates ) {
if ( ! targetStates . get ( state ) ) {
eliminateState ( matrix , state , backwardTransitions ) ;
}
}
} else {
// In this case, we perform simple state elimination in the current SCC.
dehnert
10 years ago