dftfe::ProcessGrid Class Reference

#include <process_grid.h>

Public Member Functions
	ProcessGrid (const MPI_Comm &mpi_communicator, const unsigned int n_rows, const unsigned int n_columns)
	ProcessGrid (const MPI_Comm &mpi_communicator, const unsigned int n_rows_matrix, const unsigned int n_columns_matrix, const unsigned int row_block_size, const unsigned int column_block_size)
	~ProcessGrid ()
int	get_blacs_context () const
unsigned int	get_process_grid_rows () const
unsigned int	get_process_grid_columns () const
int	get_this_process_row () const
int	get_this_process_column () const
template<typename NumberType>
void	send_to_inactive (NumberType *value, const int count=1) const
bool	is_process_active () const

Private Member Functions
	ProcessGrid (const MPI_Comm &mpi_communicator, const std::pair< unsigned int, unsigned int > &grid_dimensions)

Private Attributes
MPI_Comm	mpi_communicator
MPI_Comm	mpi_communicator_inactive_with_root
int	blacs_context
const unsigned int	this_mpi_process
const unsigned int	n_mpi_processes
int	n_process_rows
int	n_process_columns
int	this_process_row
int	this_process_column
bool	mpi_process_is_active

Friends
template<typename NumberType>
class	dftfe::ScaLAPACKMatrix

Detailed Description

A class taking care of setting up a two-dimensional processor grid. For example an MPI communicator with 5 processes can be arranged into a 2x2 grid with the 5-th processor being inactive:

     |   0     |   1
-----| ------- |-----
0    |   P0    |  P1
     |         |
-----| ------- |-----
1    |   P2    |  P3

A shared pointer to this class is provided to ScaLAPACKMatrix matrices to perform block-cyclic distribution.

Note that this class allows to setup a process grid which has fewer MPI cores than the total number of cores in the communicator.

Currently the only place where one would use a ProcessGrid object is in connection with a ScaLAPACKMatrix object.

Constructor & Destructor Documentation

ProcessGrid() [1/3]

dftfe::ProcessGrid::ProcessGrid	(	const MPI_Comm &	mpi_communicator,
		const unsigned int	n_rows,
		const unsigned int	n_columns )

Constructor for a process grid with n_rows and n_columns for a given mpi_communicator. The product of rows and columns should be less or equal to the total number of cores in the mpi_communicator.

ProcessGrid() [2/3]

dftfe::ProcessGrid::ProcessGrid	(	const MPI_Comm &	mpi_communicator,
		const unsigned int	n_rows_matrix,
		const unsigned int	n_columns_matrix,
		const unsigned int	row_block_size,
		const unsigned int	column_block_size )

$, where $M,N$ are the matrix dimension and $MB,NB$ are the block sizes and $Np$ is the number of processes in the mpi_communicator. This function then creates a 2D processor grid assuming the ratio between number of process row $p$ and columns $q$ to be equal the ratio between matrix dimensions $M$ and $N$.

For example, a square matrix $640x640$ with the block size $32$ and the mpi_communicator with 11 cores will result in the $3x3$ process grid.

~ProcessGrid()

dftfe::ProcessGrid::~ProcessGrid

(

)

Destructor.

ProcessGrid() [3/3]

dftfe::ProcessGrid::ProcessGrid ( const MPI_Comm & mpi_communicator, const std::pair< unsigned int, unsigned int > & grid_dimensions )

private

A private constructor which takes grid dimensions as an std::pair.

Member Function Documentation

get_blacs_context()

int dftfe::ProcessGrid::get_blacs_context ( ) const

inline

Return the blacs_context.

get_process_grid_columns()

unsigned int dftfe::ProcessGrid::get_process_grid_columns ( ) const

inline

Return the number of columns in the processes grid.

get_process_grid_rows()

unsigned int dftfe::ProcessGrid::get_process_grid_rows ( ) const

inline

Return the number of rows in the processes grid.

get_this_process_column()

int dftfe::ProcessGrid::get_this_process_column ( ) const

inline

Return column of this process in the process grid.

It's negative for inactive processes.

get_this_process_row()

int dftfe::ProcessGrid::get_this_process_row ( ) const

inline

Return row of this process in the process grid.

It's negative for inactive processes.

is_process_active()

bool dftfe::ProcessGrid::is_process_active ( ) const

inline

Return true if the process is active within the grid.

send_to_inactive()

template<typename NumberType>

void dftfe::ProcessGrid::send_to_inactive	(	NumberType *	value,
		const int	count = 1 ) const

Send count values stored consequently starting at value from the process with rank zero to processes which are not in the process grid.

Friends And Related Symbol Documentation

dftfe::ScaLAPACKMatrix

template<typename NumberType>

friend class dftfe::ScaLAPACKMatrix

friend

Member Data Documentation

blacs_context

int dftfe::ProcessGrid::blacs_context

private

BLACS context. This is equivalent to MPI communicators and is used by ScaLAPACK.

mpi_communicator

MPI_Comm dftfe::ProcessGrid::mpi_communicator

private

An MPI communicator with all processes (active and inactive).

mpi_communicator_inactive_with_root

MPI_Comm dftfe::ProcessGrid::mpi_communicator_inactive_with_root

private

An MPI communicator with inactive processes and the process with rank zero.

mpi_process_is_active

bool dftfe::ProcessGrid::mpi_process_is_active

private

A flag which is true for processes within the 2D process grid.

n_mpi_processes

const unsigned int dftfe::ProcessGrid::n_mpi_processes

private

Total number of MPI processes.

n_process_columns

int dftfe::ProcessGrid::n_process_columns

private

Number of columns in the processes grid.

n_process_rows

int dftfe::ProcessGrid::n_process_rows

private

Number of rows in the processes grid.

this_mpi_process

const unsigned int dftfe::ProcessGrid::this_mpi_process

private

Rank of this MPI process.

this_process_column

int dftfe::ProcessGrid::this_process_column

private

Column of this process in the grid.

It's negative for in-active processes.

this_process_row

int dftfe::ProcessGrid::this_process_row

private

Row of this process in the grid.

It's negative for in-active processes.

---

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

• workspace/include/process_grid.h