Nonowning view of a square dense block in a block matrix. More...

#include <Tpetra_Experimental_BlockView.hpp>

Public Member Functions
	LittleBlock (Scalar *const A, const LO blockSize, const LO strideX, const LO strideY)
	Constructor. More...

template<class T >
	LittleBlock (T const A, const LO blockSize, const LO strideX, const LO strideY, typename std::enable_if< !std::is_same< Scalar, T >::value &&std::is_convertible< Scalar, T >::value &&sizeof(Scalar)==sizeof(T), int >::type ignoreMe=NULL)
	Constructor that takes an `impl_scalar_type` pointer. More...

LO	getBlockSize () const
	The block size (number of rows, and number of columns). More...

Scalar *	getRawPtr () const
	Pointer to the block's entries, as `Scalar*`. More...

impl_scalar_type &	operator() (const LO i, const LO j) const
	Reference to entry (i,j) of the block. More...

template<class LittleBlockType >
void	update (const Scalar &alpha, const LittleBlockType &X) const
	`this := this + alpha * X`. More...

template<class LittleBlockType >
void	assign (const LittleBlockType &X) const
	`*this := X`. More...

void	scale (const Scalar &alpha) const
	`(this)(i,j) := alpha (*this)(i,j)` for all (i,j). More...

void	fill (const Scalar &alpha) const
	`(*this)(i,j) := alpha` for all (i,j). More...

template<class LittleBlockType >
void	absmax (const LittleBlockType &X) const
	`(this)(i,j) := max(abs((this)(i,j)), abs(X(i,j)))` for all (i,j). More...

Detailed Description

template<class Scalar, class LO>
class Tpetra::Experimental::LittleBlock< Scalar, LO >

Nonowning view of a square dense block in a block matrix.

Template Parameters

Scalar	The type of entries in the block.
LO	The type of local indices. See the documentation of the first template parameter of Map for requirements.

"Little" means local (not distributed over multiple MPI processes; stored to maximize locality) and small (think 3x3, not 1000x1000).

The Scalar template parameter may be const or nonconst. This is one reason why instance methods below that take a LittleBlock accept it as a template parameter: that lets you add a const LittleBlock (e.g., LittleBlock<const double, int>) to a nonconst LittleBlock (e.g., LittleBlock<double, int>).

Definition at line 131 of file Tpetra_Experimental_BlockView.hpp.

Constructor & Destructor Documentation

template<class Scalar , class LO >

Tpetra::Experimental::LittleBlock< Scalar, LO >::LittleBlock	(	Scalar *const	A,
		const LO	blockSize,
		const LO	strideX,
		const LO	strideY
	)

inline

Constructor.

Parameters

A	[in] Pointer to the block's entries
blockSize	[in] Dimension of the block (all blocks are square)
strideX	[in] Stride between consecutive entries in a column
strideY	[in] Stride between consecutive entries in a row

Definition at line 145 of file Tpetra_Experimental_BlockView.hpp.

template<class Scalar , class LO >

template<class T >

Tpetra::Experimental::LittleBlock< Scalar, LO >::LittleBlock	(	T *const	A,
		const LO	blockSize,
		const LO	strideX,
		const LO	strideY,
		typename std::enable_if< !std::is_same< Scalar, T >::value &&std::is_convertible< Scalar, T >::value &&sizeof(Scalar)==sizeof(T), int * >::type	ignoreMe = `NULL`
	)

inline

Constructor that takes an impl_scalar_type pointer.

Parameters

A	[in] Pointer to the block's entries, as `impl_scalar_type` rather than `Scalar`
blockSize	[in] Dimension of the block (all blocks are square)
strideX	[in] Stride between consecutive entries in a column
strideY	[in] Stride between consecutive entries in a row

While this constructor is templated on a type T, the intent is that T == impl_scalar_type. (We must template on T rather than using impl_scalar_type directly, because of how std::enable_if works.) The long, complicated std::enable_if expression ensures that this constructor only exists if Scalar differs from impl_scalar_type, but the two types are mutually compatible and have the same size. (They must be bitwise compatible, so that reinterpret_cast makes sense between them.)

Definition at line 173 of file Tpetra_Experimental_BlockView.hpp.

Member Function Documentation

template<class Scalar , class LO >

LO Tpetra::Experimental::LittleBlock< Scalar, LO >::getBlockSize ( ) const

inline

The block size (number of rows, and number of columns).

Definition at line 189 of file Tpetra_Experimental_BlockView.hpp.

template<class Scalar , class LO >

Scalar* Tpetra::Experimental::LittleBlock< Scalar, LO >::getRawPtr ( ) const

inline

Pointer to the block's entries, as Scalar*.

Definition at line 194 of file Tpetra_Experimental_BlockView.hpp.

template<class Scalar , class LO >

impl_scalar_type& Tpetra::Experimental::LittleBlock< Scalar, LO >::operator()	(	const LO	i,
		const LO	j
	)		const

inline

Reference to entry (i,j) of the block.

Note: To Tpetra developers: This is returned as impl_scalar_type and not as Scalar, in order to avoid a lot of reinterpret_cast calls in the inner loop of the sparse matrix-vector multiply kernel of Tpetra::Experimental::BlockCrsMatrix. Any pair of types impl_scalar_type, Scalar used here should always be convertible in either direction, so the return type should not pose any issues in practice.

Definition at line 208 of file Tpetra_Experimental_BlockView.hpp.

template<class Scalar , class LO >

template<class LittleBlockType >

void Tpetra::Experimental::LittleBlock< Scalar, LO >::update	(	const Scalar &	alpha,
		const LittleBlockType &	X
	)		const

inline

*this := *this + alpha * X.

Definition at line 214 of file Tpetra_Experimental_BlockView.hpp.

template<class Scalar , class LO >

template<class LittleBlockType >

void Tpetra::Experimental::LittleBlock< Scalar, LO >::assign ( const LittleBlockType & X ) const

inline

*this := X.

Definition at line 225 of file Tpetra_Experimental_BlockView.hpp.

template<class Scalar , class LO >

void Tpetra::Experimental::LittleBlock< Scalar, LO >::scale ( const Scalar & alpha ) const

inline

(*this)(i,j) := alpha * (*this)(i,j) for all (i,j).

Definition at line 234 of file Tpetra_Experimental_BlockView.hpp.

template<class Scalar , class LO >

void Tpetra::Experimental::LittleBlock< Scalar, LO >::fill ( const Scalar & alpha ) const

inline

(*this)(i,j) := alpha for all (i,j).

Definition at line 244 of file Tpetra_Experimental_BlockView.hpp.

template<class Scalar , class LO >

template<class LittleBlockType >

void Tpetra::Experimental::LittleBlock< Scalar, LO >::absmax ( const LittleBlockType & X ) const

inline

(*this)(i,j) := max(abs((*this)(i,j)), abs(X(i,j))) for all (i,j).

Tpetra uses this operation to implement the ABSMAX CombineMode.

Definition at line 258 of file Tpetra_Experimental_BlockView.hpp.

The documentation for this class was generated from the following file:

Tpetra_Experimental_BlockView.hpp

Public Member Functions

Detailed Description

template<class Scalar, class LO> class Tpetra::Experimental::LittleBlock< Scalar, LO >

Constructor & Destructor Documentation

Member Function Documentation

template<class Scalar, class LO>
class Tpetra::Experimental::LittleBlock< Scalar, LO >