/// \brief Compute QR factorization [Q,R] = qr(A,0).
///
/// \param A [in/out] On input: the multivector to factor.
/// Overwritten with garbage on output.
///
/// \param Q [out] On output: the (explicitly stored) Q factor in
/// the QR factorization of the (input) multivector A.
///
/// \param R [out] On output: the R factor in the QR factorization
/// of the (input) multivector A.
///
/// \param forceNonnegativeDiagonal [in] If true, then (if
/// necessary) do extra work (modifying both the Q and R
/// factors) in order to force the R factor to have a
/// nonnegative diagonal.
///
/// \warning Currently, this method only works if A and Q have the
/// same communicator and row distribution ("Map," in Petra
/// terms) as those of the multivector given to this adapter
/// instance's constructor. Otherwise, the result of this
/// method is undefined.
void
factorExplicit (MV& A,
MV& Q,
dense_matrix_type& R,
const bool forceNonnegativeDiagonal=false)
{
TEUCHOS_TEST_FOR_EXCEPTION
(! A.isConstantStride (), std::invalid_argument, "TsqrAdaptor::"
"factorExplicit: Input MultiVector A must have constant stride.");
TEUCHOS_TEST_FOR_EXCEPTION
(! Q.isConstantStride (), std::invalid_argument, "TsqrAdaptor::"
"factorExplicit: Input MultiVector Q must have constant stride.");
prepareTsqr (Q); // Finish initializing TSQR.
// FIXME (mfh 16 Jan 2016) Currently, TSQR is a host-only
// implementation.
A.template sync<Kokkos::HostSpace> ();
A.template modify<Kokkos::HostSpace> ();
Q.template sync<Kokkos::HostSpace> ();
Q.template modify<Kokkos::HostSpace> ();
auto A_view = A.template getLocalView<Kokkos::HostSpace> ();
auto Q_view = Q.template getLocalView<Kokkos::HostSpace> ();
scalar_type* const A_ptr =
reinterpret_cast<scalar_type*> (A_view.ptr_on_device ());
scalar_type* const Q_ptr =
reinterpret_cast<scalar_type*> (Q_view.ptr_on_device ());
const bool contiguousCacheBlocks = false;
tsqr_->factorExplicitRaw (A_view.dimension_0 (),
A_view.dimension_1 (),
A_ptr, A.getStride (),
Q_ptr, Q.getStride (),
R.values (), R.stride (),
contiguousCacheBlocks,
forceNonnegativeDiagonal);
}
/// \brief Rank-revealing decomposition
///
/// Using the R factor and explicit Q factor from
/// factorExplicit(), compute the singular value decomposition
/// (SVD) of R: \f$R = U \Sigma V^*\f$. If R is full rank (with
/// respect to the given relative tolerance \c tol), do not modify
/// Q or R. Otherwise, compute \f$Q := Q \cdot U\f$ and \f$R :=
/// \Sigma V^*\f$ in place. If R was modified, then it may not
/// necessarily be upper triangular on output.
///
/// \param Q [in/out] On input: explicit Q factor computed by
/// factorExplicit(). (Must be an orthogonal resp. unitary
/// matrix.) On output: If R is of full numerical rank with
/// respect to the tolerance tol, Q is unmodified. Otherwise, Q
/// is updated so that the first \c rank columns of Q are a
/// basis for the column space of A (the original matrix whose
/// QR factorization was computed by factorExplicit()). The
/// remaining columns of Q are a basis for the null space of A.
///
/// \param R [in/out] On input: N by N upper triangular matrix
/// with leading dimension LDR >= N. On output: if input is
/// full rank, R is unchanged on output. Otherwise, if \f$R = U
/// \Sigma V^*\f$ is the SVD of R, on output R is overwritten
/// with \f$\Sigma \cdot V^*\f$. This is also an N by N matrix,
/// but it may not necessarily be upper triangular.
///
/// \param tol [in] Relative tolerance for computing the numerical
/// rank of the matrix R.
///
/// \return Rank \f$r\f$ of R: \f$ 0 \leq r \leq N\f$.
int
revealRank (MV& Q,
dense_matrix_type& R,
const magnitude_type& tol)
{
TEUCHOS_TEST_FOR_EXCEPTION
(! Q.isConstantStride (), std::invalid_argument, "TsqrAdaptor::"
"revealRank: Input MultiVector Q must have constant stride.");
prepareTsqr (Q); // Finish initializing TSQR.
// FIXME (mfh 18 Oct 2010) Check Teuchos::Comm<int> object in Q
// to make sure it is the same communicator as the one we are
// using in our dist_tsqr_type implementation.
Q.template sync<Kokkos::HostSpace> ();
Q.template modify<Kokkos::HostSpace> ();
auto Q_view = Q.template getLocalView<Kokkos::HostSpace> ();
scalar_type* const Q_ptr =
reinterpret_cast<scalar_type*> (Q_view.ptr_on_device ());
const bool contiguousCacheBlocks = false;
return tsqr_->revealRankRaw (Q_view.dimension_0 (),
Q_view.dimension_1 (),
Q_ptr, Q.getStride (),
R.values (), R.stride (),
tol, contiguousCacheBlocks);
}
/// \brief Extract A's underlying KokkosClassic::MultiVector instance.
///
/// TSQR represents the local (to each MPI process) part of a
/// multivector as a KokkosClassic::MultiVector (KMV), which gives a
/// nonconstant view of the original multivector's data. This
/// class method tells TSQR how to get the KMV from the input
/// multivector. The KMV is not a persistent view of the data;
/// its scope is contained within the scope of the multivector.
///
/// \warning TSQR does not currently support multivectors with
/// nonconstant stride. If A has nonconstant stride, this
/// method will throw an exception.
static KokkosClassic::MultiVector<scalar_type, node_type>
getNonConstView (MV& A)
{
// FIXME (mfh 25 Oct 2010) We should be able to run TSQR even if
// storage of A uses nonconstant stride internally. We would
// have to copy and pack into a matrix with constant stride, and
// then unpack on exit. For now we choose just to raise an
// exception.
TEUCHOS_TEST_FOR_EXCEPTION(! A.isConstantStride(), std::invalid_argument,
"TSQR does not currently support Tpetra::MultiVector "
"inputs that do not have constant stride.");
return A.getLocalMVNonConst();
}
/// \brief Extract A's underlying KokkosClassic::MultiVector instance.
///
/// TSQR represents the local (to each MPI process) part of a
/// multivector as a KokkosClassic::MultiVector (KMV), which gives a
/// nonconstant view of the original multivector's data. This
/// class method tells TSQR how to get the KMV from the input
/// multivector. The KMV is not a persistent view of the data;
/// its scope is contained within the scope of the multivector.
///
/// \warning TSQR does not currently support multivectors with
/// nonconstant stride. If A has nonconstant stride, this
/// method will throw an exception.
static KokkosClassic::MultiVector<scalar_type, node_type>
getNonConstView (MV& A)
{
// FIXME (mfh 25 Oct 2010) We should be able to run TSQR even if
// storage of A uses nonconstant stride internally. We would
// have to copy and pack into a matrix with constant stride, and
// then unpack on exit. For now we choose just to raise an
// exception.
TEUCHOS_TEST_FOR_EXCEPTION(! A.isConstantStride(), std::invalid_argument,
"TSQR does not currently support Tpetra::MultiVector "
"inputs that do not have constant stride.");
typedef typename Teuchos::ArrayRCP<mp_scalar_type>::size_type size_type;
typedef typename MV::dual_view_type view_type;
typedef typename view_type::t_dev::array_type flat_array_type;
// Create new Kokkos::MultiVector reinterpreting the data as a longer
// array of the base scalar type
// Create new ArrayRCP holding data
view_type pce_mv = A.getDualView();
flat_array_type flat_mv = pce_mv.d_view;
const size_t num_rows = flat_mv.dimension_0();
const size_t num_cols = flat_mv.dimension_1();
const size_t size = num_rows * num_cols;
ArrayRCP<scalar_type> vals =
Teuchos::arcp(flat_mv.ptr_on_device(), size_type(0), size, false);
// Create new MultiVector
// Owing to the above comment, we don't need to worry about
// non-constant stride
size_t strides[2];
flat_mv.stride(strides);
const size_t stride = strides[0];
KokkosClassic::MultiVector<scalar_type, node_type> mv(A.getMap()->getNode());
mv.initializeValues(num_rows, num_cols, vals, stride);
return mv;
}
//! Do the transpose or conjugate transpose solve.
void applyTranspose (const MV& X_in, MV& Y_in, const Teuchos::ETransp mode) const
{
typedef Teuchos::ScalarTraits<Scalar> ST;
using Teuchos::null;
TEUCHOS_TEST_FOR_EXCEPTION
(mode != Teuchos::TRANS && mode != Teuchos::CONJ_TRANS, std::logic_error,
"Tpetra::CrsMatrixSolveOp::applyTranspose: mode is neither TRANS nor "
"CONJ_TRANS. Should never get here! Please report this bug to the "
"Tpetra developers.");
const size_t numVectors = X_in.getNumVectors();
Teuchos::RCP<const Import<LocalOrdinal,GlobalOrdinal,Node> > importer =
matrix_->getGraph ()->getImporter ();
Teuchos::RCP<const Export<LocalOrdinal,GlobalOrdinal,Node> > exporter =
matrix_->getGraph ()->getExporter ();
Teuchos::RCP<const MV> X;
// it is okay if X and Y reference the same data, because we can
// perform a triangular solve in-situ. however, we require that
// column access to each is strided.
// set up import/export temporary multivectors
if (importer != null) {
if (importMV_ != null && importMV_->getNumVectors() != numVectors) {
importMV_ = null;
}
if (importMV_ == null) {
importMV_ = Teuchos::rcp( new MV(matrix_->getColMap(),numVectors) );
}
}
if (exporter != null) {
if (exportMV_ != null && exportMV_->getNumVectors() != numVectors) {
exportMV_ = null;
}
if (exportMV_ == null) {
exportMV_ = Teuchos::rcp( new MV(matrix_->getRowMap(),numVectors) );
}
}
// solve(TRANS): DomainMap -> RangeMap
// lclMatSolve_(TRANS): ColMap -> RowMap
// importer: DomainMap -> ColMap
// exporter: RowMap -> RangeMap
//
// solve = importer o lclMatSolve_ o exporter
// Domainmap -> ColMap -> RowMap -> RangeMap
//
// If we have a non-trivial importer, we must import elements that
// are permuted or are on other processes.
if (importer != null) {
importMV_->doImport(X_in,*importer,INSERT);
X = importMV_;
}
else if (X_in.isConstantStride() == false) {
// cannot handle non-constant stride right now
// generate a copy of X_in
X = Teuchos::rcp(new MV(X_in));
}
else {
// just temporary, so this non-owning RCP is okay
X = Teuchos::rcpFromRef (X_in);
}
// If we have a non-trivial exporter, we must export elements that
// are permuted or belong to other processes. We will compute
// solution into the to-be-exported MV; get a view.
if (exporter != null) {
matrix_->template localSolve<Scalar, Scalar> (*X, *exportMV_,
Teuchos::CONJ_TRANS);
// Make sure target is zero: necessary because we are adding
Y_in.putScalar(ST::zero());
Y_in.doExport(*importMV_, *importer, ADD);
}
// otherwise, solve into Y
else {
if (Y_in.isConstantStride() == false) {
// generate a strided copy of Y
MV Y(Y_in);
matrix_->template localSolve<Scalar, Scalar> (*X, Y, Teuchos::CONJ_TRANS);
Y_in = Y;
}
else {
matrix_->template localSolve<Scalar, Scalar> (*X, Y_in, Teuchos::CONJ_TRANS);
}
}
}
//! Do the non-transpose solve.
void applyNonTranspose (const MV& X_in, MV& Y_in) const
{
using Teuchos::NO_TRANS;
using Teuchos::null;
typedef Teuchos::ScalarTraits<Scalar> ST;
// Solve U X = Y or L X = Y
// X belongs to domain map, while Y belongs to range map
const size_t numVectors = X_in.getNumVectors();
Teuchos::RCP<const Import<LocalOrdinal,GlobalOrdinal,Node> > importer =
matrix_->getGraph ()->getImporter ();
Teuchos::RCP<const Export<LocalOrdinal,GlobalOrdinal,Node> > exporter =
matrix_->getGraph ()->getExporter ();
Teuchos::RCP<const MV> X;
// it is okay if X and Y reference the same data, because we can
// perform a triangular solve in-situ. however, we require that
// column access to each is strided.
// set up import/export temporary multivectors
if (importer != null) {
if (importMV_ != null && importMV_->getNumVectors () != numVectors) {
importMV_ = null;
}
if (importMV_ == null) {
importMV_ = Teuchos::rcp (new MV (matrix_->getColMap (), numVectors));
}
}
if (exporter != null) {
if (exportMV_ != null && exportMV_->getNumVectors () != numVectors) {
exportMV_ = null;
}
if (exportMV_ == null) {
exportMV_ = Teuchos::rcp (new MV (matrix_->getRowMap (), numVectors));
}
}
// solve(NO_TRANS): RangeMap -> DomainMap
// lclMatSolve_: RowMap -> ColMap
// importer: DomainMap -> ColMap
// exporter: RowMap -> RangeMap
//
// solve = reverse(exporter) o lclMatSolve_ o reverse(importer)
// RangeMap -> RowMap -> ColMap -> DomainMap
//
// If we have a non-trivial exporter, we must import elements that
// are permuted or are on other processors
if (exporter != null) {
exportMV_->doImport (X_in, *exporter, INSERT);
X = exportMV_;
}
else if (! X_in.isConstantStride ()) {
// cannot handle non-constant stride right now
// generate a copy of X_in
X = Teuchos::rcp (new MV (X_in));
}
else {
// just temporary, so this non-owning RCP is okay
X = Teuchos::rcpFromRef (X_in);
}
// If we have a non-trivial importer, we must export elements that
// are permuted or belong to other processes. We will compute
// solution into the to-be-exported MV.
if (importer != null) {
matrix_->template localSolve<Scalar, Scalar> (*X, *importMV_, NO_TRANS);
// Make sure target is zero: necessary because we are adding.
Y_in.putScalar (ST::zero ());
Y_in.doExport (*importMV_, *importer, ADD);
}
// otherwise, solve into Y
else {
// can't solve into non-strided multivector
if (! Y_in.isConstantStride ()) {
// generate a strided copy of Y
MV Y (Y_in);
matrix_->template localSolve<Scalar, Scalar> (*X, Y, NO_TRANS);
Tpetra::deep_copy (Y_in, Y);
}
else {
matrix_->template localSolve<Scalar, Scalar> (*X, Y_in, NO_TRANS);
}
}
}
