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Calculating steady state using standard equation system for eigenvectors, removed all-in-one matrix transformation (nicer looking code) 

Former-commit-id: 2502615686
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David_Korzeniewski 11 years ago
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04c1d51313
commit
a448cd8973
1 changed files with 34 additions and 126 deletions
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  1. 160
      src/modelchecker/prctl/SparseDtmcPrctlModelChecker.cpp

160
src/modelchecker/prctl/SparseDtmcPrctlModelChecker.cpp
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@ -403,147 +403,55 @@ namespace storm {
subsystem.set(bscc.begin(), bscc.end());
//we now have to solve ((P')^t - I) * x = 0, where P' is the submatrix of transitionMatrix,
// ^t means transose, and I is the identity matrix. As a memory optimisation, we calculate
// ((P')^t - I) in one step from transitionMatrix instead of calling the appropriate methods
// ^t means transose, and I is the identity matrix.
// First, we need to determine the number of entries and the number of rows of the submatrix.
typename transitionMatrix::index_type subEntries = 0;
typename transitionMatrix::index_type subRows = 0;
for (auto index : rowGroupConstraint) {
subRows += rowGroupIndices[index + 1] - rowGroupIndices[index];
for (index_type i = rowGroupIndices[index]; i < rowGroupIndices[index + 1]; ++i) {
bool foundDiagonalElement = false;
for (const_iterator it = transitionMatrix->begin(i), ite = transitionMatrix->end(i); it != ite; ++it) {
if (columnConstraint.get(it->getColumn())) {
++subEntries;
if (index == it->getColumn()) {
foundDiagonalElement = true;
}
}
}
// If requested, we need to reserve one entry more for inserting the diagonal zero entry.
if (!foundDiagonalElement) {
++subEntries;
storm::storage::SparseMatrix<ValueType> subsystemMatrix = transitionMatrix.getSubmatrix(false, subsystem, subsystem, true);
subsystemMatrix = subsystemMatrix.transpose();
// subtract 1 on the diagonal and at the same time add a row with all ones to enforce that the result of the equation system is unique
storm::storage::SparseMatrixBuilder<ValueType> equationSystemBuilder(subsystemMatrix.getRowCount() + 1, subsystemMatrix.getColumnCount(), subsystemMatrix.getEntryCount() + subsystemMatrix.getColumnCount());
ValueType one = storm::utility::one<ValueType>();
ValueType zero = storm::utility::zero<ValueType>();
bool foundDiagonalElement = false;
for (uint_fast64_t row = 0; row < subsystemMatrix.getRowCount(); ++row) {
for (auto& entry : subsystemMatrix.getRowGroup(row)) {
if (entry.getColumn() == row) {
equationSystemBuilder.addNextValue(row, entry.getColumn(), entry.getValue() - one);
foundDiagonalElement = true;
} else {
equationSystemBuilder.addNextValue(row, entry.getColumn(), entry.getValue());
}
}
}
// Create a temporary vector that stores for each index whose bit is set to true the number of bits that
// were set before that particular index.
std::vector<index_type> bitsSetBeforeIndex;
bitsSetBeforeIndex.reserve(columnCount);
// Compute the information to fill this vector.
index_type lastIndex = 0;
index_type currentNumberOfSetBits = 0;
// If we are requested to add missing diagonal entries, we need to make sure the corresponding rows are also
// taken.
storm::storage::BitVector columnBitCountConstraint = columnConstraint;
if (insertDiagonalEntries) {
columnBitCountConstraint |= rowGroupConstraint;
}
for (auto index : columnBitCountConstraint) {
while (lastIndex <= index) {
bitsSetBeforeIndex.push_back(currentNumberOfSetBits);
++lastIndex;
}
++currentNumberOfSetBits;
// Throw an exception if a row did not have an element on the diagonal.
STORM_LOG_THROW(foundDiagonalElement, storm::exceptions::InvalidOperationException, "Internal Error, no diagonal entry found.");
}
// Copy over selected entries.
index_type rowCount = 0;
for (auto index : rowGroupConstraint) {
matrixBuilder.newRowGroup(rowCount);
for (index_type i = rowGroupIndices[index]; i < rowGroupIndices[index + 1]; ++i) {
bool insertedDiagonalElement = false;
for (const_iterator it = this->begin(i), ite = this->end(i); it != ite; ++it) {
if (columnConstraint.get(it->getColumn())) {
if (index == it->getColumn()) {
insertedDiagonalElement = true;
} else if (insertDiagonalEntries && !insertedDiagonalElement && it->getColumn() > index) {
matrixBuilder.addNextValue(rowCount, bitsSetBeforeIndex[index], storm::utility::zero<ValueType>());
insertedDiagonalElement = true;
}
matrixBuilder.addNextValue(rowCount, bitsSetBeforeIndex[it->getColumn()], it->getValue());
}
}
if (insertDiagonalEntries && !insertedDiagonalElement) {
matrixBuilder.addNextValue(rowCount, bitsSetBeforeIndex[index], storm::utility::zero<ValueType>());
}
++rowCount;
}
for (uint_fast64_t column = 0; column + 1 < subsystemMatrix.getColumnCount(); ++column) {
equationSystemBuilder.addNextValue(subsystemMatrix.getRowCount(), column, one);
}
matrixBuilder.build();
equationSystemBuilder.addNextValue(subsystemMatrix.getRowCount(), subsystemMatrix.getColumnCount() - 1, zero);
subsystemMatrix = equationSystemBuilder.build();
//transpose code
std::vector<index_type> rowIndications(rowCount + 1);
std::vector<MatrixEntry<index_type, ValueType>> columnsAndValues(entryCount);
// create x and b for the equation system. setting the last entry of b to one enforces the sum over the unique solution vector is one
std::vector<ValueType> steadyStateDist(subsystemMatrix.getRowCount(), zero);
std::vector<ValueType> b(subsystemMatrix.getRowCount(), zero);
b[subsystemMatrix.getRowCount() - 1] = one;
// First, we need to count how many entries each column has.
for (index_type group = 0; group < columnCount; ++group) {
for (auto const& transition : transitionMatrix->getRow(group)) {
if (!comparator.isZero(transition.getValue())) {
++rowIndications[transition.getColumn() + 1];
}
}
}
solver->solveEquationSystem(subsystemMatrix, steadyStateDist, b);
// Now compute the accumulated offsets.
for (index_type i = 1; i < rowCount + 1; ++i) {
rowIndications[i] = rowIndications[i - 1] + rowIndications[i];
}
// Create an array that stores the index for the next value to be added for
// each row in the transposed matrix. Initially this corresponds to the previously
// computed accumulated offsets.
std::vector<index_type> nextIndices = rowIndications;
// Now we are ready to actually fill in the values of the transposed matrix.
for (index_type group = 0; group < columnCount; ++group) {
for (auto const& transition : transitionMatrix->getRow(group)) {
if (!comparator.isZero(transition.getValue())) {
columnsAndValues[nextIndices[transition.getColumn()]] = std::make_pair(group, transition.getValue());
nextIndices[transition.getColumn()]++;
}
}
}
std::vector<index_type> rowGroupIndices(rowCount + 1);
for (index_type i = 0; i <= rowCount; ++i) {
rowGroupIndices[i] = i;
}
storm::storage::SparseMatrix<ValueType> transposedMatrix(columnCount, std::move(rowIndications), std::move(columnsAndValues), std::move(rowGroupIndices));
/*
storm::storage::SparseMatrix<ValueType> subsystemMatrix = transitionMatrix.getSubmatrix(false, subsystem, subsystem);
std::vector<ValueType> steadyStateDist(subsystemMatrix.getRowCount(), storm::utility::zero<ValueType>());
steadyStateDist[0] = storm::utility::one<ValueType>();
solver->solveEquationSystem(subsystemMatrix, steadyStateDist, steadyStateDist);
ValueType length = storm::utility::zero<ValueType>();
for (auto value : steadyStateDist) {
length += value;
}
storm::utility::vector::scaleVectorInPlace(steadyStateDist, storm::utility::one<ValueType>() / length);
std::vector<ValueType> steadyStateForPsiStates(transitionMatrix.getRowCount(), storm::utility::zero<ValueType>());
//remove the last entry of the vector as it was just there to enforce the unique solution
steadyStateDist.pop_back();
//calculate the fraction we spend in psi states on the long run
std::vector<ValueType> steadyStateForPsiStates(transitionMatrix.getRowCount() - 1, zero);
storm::utility::vector::setVectorValues(steadyStateForPsiStates, psiStates & subsystem, steadyStateDist);
ValueType result = storm::utility::zero<ValueType>();
ValueType result = zero;
for (auto value : steadyStateForPsiStates) {
result += value;
}
*/
return result;
}

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