sc_allgather.h File Reference

Self-contained implementation of MPI_Allgather. More...

#include <sc.h>

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Macros
#define	SC_ALLGATHER_ALLTOALL_MAX   5
	The largest group size that uses direct all-to-all.

Functions
void	sc_allgather_alltoall (sc_MPI_Comm mpicomm, char *data, int datasize, int groupsize, int myoffset, int myrank)
	Allgather by direct point-to-point communication. More...
void	sc_allgather_recursive (sc_MPI_Comm mpicomm, char *data, int datasize, int groupsize, int myoffset, int myrank)
	Perform recursive bisection allgather. More...
int	sc_allgather (void *sendbuf, int sendcount, sc_MPI_Datatype sendtype, void *recvbuf, int recvcount, sc_MPI_Datatype recvtype, sc_MPI_Comm mpicomm)
	Drop-in allgather replacement. More...

Detailed Description

Self-contained implementation of MPI_Allgather.

The algorithm uses a binary communication tree. The recursion terminates at a specified depth by an all-to-all step.

Function Documentation

sc_allgather()

int sc_allgather	(	void *	sendbuf,
		int	sendcount,
		sc_MPI_Datatype	sendtype,
		void *	recvbuf,
		int	recvcount,
		sc_MPI_Datatype	recvtype,
		sc_MPI_Comm	mpicomm
	)

Drop-in allgather replacement.

Parameters

[in]	sendbuf	Send buffer conforming to MPI specification.
[in]	sendcount	Number of data items to send.
[in]	sendtype	Valid MPI Datatype.
[out]	recvbuf	Receive buffer conforming to MPI specification.
[in]	recvcount	Number of data items to receive.
[in]	recvtype	Valid MPI Datatype.
[in]	mpicomm	Valid MPI communicator.

Returns

int sc_MPI_SUCCESS if not aborting on MPI error.

sc_allgather_alltoall()

void sc_allgather_alltoall	(	sc_MPI_Comm	mpicomm,
		char *	data,
		int	datasize,
		int	groupsize,
		int	myoffset,
		int	myrank
	)

Allgather by direct point-to-point communication.

This function is only efficient for small group sizes.

Parameters

[in]	mpicomm	Valid MPI communicator.
[in,out]	data	Send and receive buffer for a subgroup of the communicator.
[in]	datasize	Number of bytes to send.
[in]	groupsize	Number of processes in the subgroup.
[in]	myoffset	Offset of the subgroup in the communicator.
[in]	myrank	MPI rank in the communicator.

sc_allgather_recursive()

void sc_allgather_recursive	(	sc_MPI_Comm	mpicomm,
		char *	data,
		int	datasize,
		int	groupsize,
		int	myoffset,
		int	myrank
	)

Perform recursive bisection allgather.

When size becomes less equal SC_ALLGATHER_ALLTOALL_MAX, call sc_allgather_alltoall.

Parameters

[in]	mpicomm	Valid MPI communicator.
[in,out]	data	Send and receive buffer for a subgroup of the communicator.
[in]	datasize	Number of bytes to send.
[in]	groupsize	Number of processes in the subgroup.
[in]	myoffset	Offset of the subgroup in the communicator.
[in]	myrank	MPI rank in the communicator.