DNDS::GlobalOffsetsMapping Class Reference

Table mapping rank-local row indices to the global index space. More...

#include <IndexMapping.hpp>

Public Member Functions
t_IndexVec &	RLengths ()
	Per-rank lengths vector (size == nRanks).
t_IndexVec &	ROffsets ()
	Prefix-sum offsets vector (size == nRanks + 1, last element == globalSize).
index	globalSize () const
	Total number of rows across all ranks.
void	setMPIAlignBcast (const MPIInfo &mpi, index myLength)
	Broadcast each rank's length, then compute the global prefix sums.
index	operator() (MPI_int rank, index val) const
	Convert a (rank, local) pair to a global index.
bool	search (index globalQuery, MPI_int &rank, index &val) const
	Convert a global index to (rank, local). Returns false if out of range.
std::tuple< bool, MPI_int, index >	search (index globalQuery) const

Detailed Description

Table mapping rank-local row indices to the global index space.

Every rank owns a contiguous chunk in the global index space:

rank:           0    1    2
RankLengths = [ 3,   4,   5 ]
RankOffsets = [ 0,   3,   7,  12 ]  # prefix sum, size == nRanks + 1

After setMPIAlignBcast, every rank holds an identical copy of the table (it is globally replicated), so both local-to-global (operator()) and global-to-local (search) queries are purely local. Used by ParArraycreateGlobalMapping and friends.

Definition at line 44 of file IndexMapping.hpp.

Member Function Documentation

globalSize()

index DNDS::GlobalOffsetsMapping::globalSize ( ) const

inline

Total number of rows across all ranks.

Definition at line 58 of file IndexMapping.hpp.

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operator()()

index DNDS::GlobalOffsetsMapping::operator() ( MPI_int  rank, index  val  ) const

inline

Convert a (rank, local) pair to a global index.

Equivalent to RankOffsets[rank] + val, with asserts.

Definition at line 95 of file IndexMapping.hpp.

RLengths()

t_IndexVec & DNDS::GlobalOffsetsMapping::RLengths ( )

inline

Per-rank lengths vector (size == nRanks).

Definition at line 53 of file IndexMapping.hpp.

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ROffsets()

t_IndexVec & DNDS::GlobalOffsetsMapping::ROffsets ( )

inline

Prefix-sum offsets vector (size == nRanks + 1, last element == globalSize).

Definition at line 55 of file IndexMapping.hpp.

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search() [1/2]

std::tuple< bool, MPI_int, index > DNDS::GlobalOffsetsMapping::search ( index  globalQuery ) const

inline

Definition at line 133 of file IndexMapping.hpp.

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search() [2/2]

bool DNDS::GlobalOffsetsMapping::search ( index  globalQuery, MPI_int &  rank, index &  val  ) const

inline

Convert a global index to (rank, local). Returns false if out of range.

Uses std::lower_bound on the offsets table (O(log nRanks)).

Parameters

	globalQuery	Global index.
[out]	rank	Owning rank on success.
[out]	val	Local offset within the owner.

Returns

true if globalQuery lies within [0, globalSize()).

Definition at line 114 of file IndexMapping.hpp.

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setMPIAlignBcast()

void DNDS::GlobalOffsetsMapping::setMPIAlignBcast ( const MPIInfo &  mpi, index  myLength  )

inline

Broadcast each rank's length, then compute the global prefix sums.

Collective call. After it returns, every rank holds the full RLengths / ROffsets tables. Called by ParArray::createGlobalMapping during mesh/array setup.

Parameters

mpi	MPI context.
myLength	Number of rows owned by the calling rank.

Definition at line 72 of file IndexMapping.hpp.

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

• /home/runner/work/DNDSR/DNDSR/src/DNDS/IndexMapping.hpp