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#include "Bdef.h"
/*
* The bidirectional exchange topology (BE) is specialized for dealing with
* case where all nodes participating in the operation need to
* receive the answer. It works best when # of nodes is some even
* power of two. This topology is based on an algorithm presented by
* Robert van de Geijn, et al.
*/
void BI_BeComb(BLACSCONTEXT *ctxt, BLACBUFF *bp, BLACBUFF *bp2,
int N, VVFUNPTR Xvvop)
/*
* -- V1.1ALPHA (test version) BLACS routine --
* University of Tennessee, October 1, 1995
* Written by Clint Whaley.
*
* Purpose
* =======
* Perform a element-by-element combine on vectors.
* The answer will be left on all participating processes. Since this method
* uses a hypercube communication pattern, the number of nodes participating
* in the operation must be a power of 2 for it to perform efficiently.
*
* Arguments
* =========
* CTXT (input) pointer to BLACSCONTEXT
* The BLACS context where operation is taking place.
*
* BP (input/output) pointer to BLACBUFF.
* BLACBUFF is a special data type used by the BLACS to control
* buffers and the asynchronous operations coming out of them.
* This BLACBUFF should have a buffer who's first N elements
* contain the data to be combined. Additional space may be
* required, depending upon what combine is being performed.
*
* BP2 (workspace) pointer to BLACBUFF.
* This BLACBUFF is used to receive information for combining with
* this process's information.
*
* N (input) int
* The number of elements in the vector to be combined.
*
* Xvvop (input) pointer to typed operation function
* Points to a typed function which performs the required operation
* (e.g. summation) on the two N-element vectors.
*
* ------------------------------------------------------------------------
*/
{
void BI_Ssend(BLACSCONTEXT *, int, int, BLACBUFF *);
void BI_Srecv(BLACSCONTEXT *, int, int, BLACBUFF *);
void BI_Rsend(BLACSCONTEXT *, int, int, BLACBUFF *);
void BI_Arecv(BLACSCONTEXT *, int, int, BLACBUFF *);
void BI_UpdateBuffs(BLACBUFF *);
BLACBUFF *BI_GetBuff(int);
int BI_BuffIsFree(BLACBUFF *, int);
int Np, Iam, dest, msgid, Rmsgid, np2, bit, ierr;
extern BI_MPI_Status *BI_Stats;
Np = ctxt->scp->Np;
if (Np < 2) return;
Iam = ctxt->scp->Iam;
msgid = Mscopeid(ctxt);
Rmsgid = Mscopeid(ctxt);
for (np2=4; np2 < Np; np2 <<= 1);
if (np2 > Np) np2 >>= 1;
if (np2 != Np)
{
dest = (Iam ^ np2);
if (Iam >= np2) /* I'm node beyond power of 2 */
{
BI_Arecv(ctxt, dest, Rmsgid, bp);
BI_Ssend(ctxt, dest, msgid, bp);
BI_BuffIsFree(bp, 1);
}
else if (Iam < (Np^np2)) /* need to fan in contents of */
{ /* non-power of 2 nodes */
BI_Srecv(ctxt, dest, msgid, bp2);
Xvvop(N, bp->Buff, bp2->Buff);
}
}
if (Iam < np2)
{
for (bit=1; (bit ^ np2); bit <<= 1)
{
dest = Iam ^ bit;
BI_MPI_Sendrecv(bp->Buff, bp->N, bp->dtype, dest, msgid, bp2->Buff,
bp2->N, bp2->dtype, dest, msgid, ctxt->scp->comm,
BI_Stats, ierr);
Xvvop(N, bp->Buff, bp2->Buff);
}
/*
* For nodes that are not part of the hypercube proper, we must
* send data back.
*/
if (Iam < (Np^np2)) BI_Rsend(ctxt, (Iam ^ np2), Rmsgid, bp);
} /* end if (nodes inside power of 2) */
}
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