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2008-04-15 18:56:58 +01:00

243 lines
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C

/*
* Copyright 1997, Regents of the University of Minnesota
*
* initmsection.c
*
* This file contains code that performs the k-way multisection
*
* Started 6/3/97
* George
*
* $Id: initmsection.c,v 1.2 2003/07/21 17:18:49 karypis Exp $
*/
#include <parmetislib.h>
#define DEBUG_IPART_
/*************************************************************************
* This function is the entry point of the initial partitioning algorithm.
* This algorithm assembles the graph to all the processors and preceed
* serially.
**************************************************************************/
void InitMultisection(CtrlType *ctrl, GraphType *graph, WorkSpaceType *wspace)
{
int i, lpecut[2], gpecut[2], mypart, moptions[10];
idxtype *vtxdist, *gwhere = NULL, *part, *label;
GraphType *agraph;
int *sendcounts, *displs;
MPI_Comm newcomm, labelcomm;
IFSET(ctrl->dbglvl, DBG_TIME, starttimer(ctrl->InitPartTmr));
/* Assemble the graph and do the necessary pre-processing */
agraph = AssembleMultisectedGraph(ctrl, graph, wspace);
part = agraph->where;
agraph->where = NULL;
/* Split the processors into groups so that each one can do a bisection */
mypart = ctrl->mype%(ctrl->nparts/2);
MPI_Comm_split(ctrl->comm, mypart, 0, &newcomm);
/* Each processor keeps the graphs that it only needs and bisects it */
agraph->ncon = 1; /* needed for Moc_KeepPart */
Moc_KeepPart(agraph, wspace, part, mypart);
label = agraph->label; /* Save this because ipart may need it */
agraph->label = NULL;
/* Bisect the graph and construct the separator */
switch (ctrl->ipart) {
case ISEP_EDGE:
moptions[0] = 1;
moptions[1] = 3;
moptions[2] = 1;
moptions[3] = 1;
moptions[4] = 0;
moptions[7] = ctrl->mype;
agraph->where = idxmalloc(agraph->nvtxs, "InitMultisection: agraph->where");
METIS_EdgeComputeSeparator(&agraph->nvtxs, agraph->xadj, agraph->adjncy,
agraph->vwgt, agraph->adjwgt, moptions, &agraph->mincut, agraph->where);
break;
case ISEP_NODE:
moptions[0] = 1;
moptions[1] = 3;
moptions[2] = 1;
moptions[3] = 2;
moptions[4] = 0;
moptions[7] = ctrl->mype;
agraph->where = idxmalloc(agraph->nvtxs, "InitMultisection: agraph->where");
METIS_NodeComputeSeparator(&agraph->nvtxs, agraph->xadj, agraph->adjncy, agraph->vwgt,
agraph->adjwgt, moptions, &agraph->mincut, agraph->where);
break;
default:
errexit("Unknown ISEP type!\n");
}
for (i=0; i<agraph->nvtxs; i++) {
ASSERT(ctrl, agraph->where[i]>=0 && agraph->where[i]<=2);
if (agraph->where[i] == 2)
agraph->where[i] = ctrl->nparts+2*mypart;
else
agraph->where[i] += 2*mypart;
}
/* Determine which PE got the minimum cut */
lpecut[0] = agraph->mincut;
MPI_Comm_rank(newcomm, lpecut+1);
MPI_Allreduce(lpecut, gpecut, 1, MPI_2INT, MPI_MINLOC, newcomm);
/* myprintf(ctrl, "Nvtxs: %d, Mincut: %d, GMincut: %d, %d\n", agraph->nvtxs, agraph->mincut, gpecut[0], gpecut[1]); */
/* Send the best where to the root processor of this partition */
if (lpecut[1] == gpecut[1] && gpecut[1] != 0)
MPI_Send((void *)agraph->where, agraph->nvtxs, IDX_DATATYPE, 0, 1, newcomm);
if (lpecut[1] == 0 && gpecut[1] != 0)
MPI_Recv((void *)agraph->where, agraph->nvtxs, IDX_DATATYPE, gpecut[1], 1, newcomm, &ctrl->status);
/* Create a communicator that stores all the i-th processors of the newcomm */
MPI_Comm_split(ctrl->comm, lpecut[1], 0, &labelcomm);
/* Map the separator back to agraph. This is inefficient! */
if (lpecut[1] == 0) {
gwhere = idxsmalloc(graph->gnvtxs, 0, "InitMultisection: gwhere");
for (i=0; i<agraph->nvtxs; i++)
gwhere[label[i]] = agraph->where[i];
}
free(agraph->where);
agraph->where = part;
if (lpecut[1] == 0) {
MPI_Reduce((void *)gwhere, (void *)agraph->where, graph->gnvtxs, IDX_DATATYPE, MPI_SUM, 0, labelcomm);
free(gwhere);
}
/* The minimum PE performs the Scatter */
vtxdist = graph->vtxdist;
ASSERT(ctrl, graph->where != NULL);
free(graph->where); /* Remove the propagated down where info */
graph->where = idxmalloc(graph->nvtxs+graph->nrecv, "InitPartition: where");
sendcounts = imalloc(ctrl->npes, "InitPartitionNew: sendcounts");
displs = imalloc(ctrl->npes, "InitPartitionNew: displs");
for (i=0; i<ctrl->npes; i++) {
sendcounts[i] = vtxdist[i+1]-vtxdist[i];
displs[i] = vtxdist[i];
}
MPI_Scatterv((void *)agraph->where, sendcounts, displs, IDX_DATATYPE,
(void *)graph->where, graph->nvtxs, IDX_DATATYPE, 0, ctrl->comm);
GKfree((void **)&sendcounts, (void **)&displs, (void **)&label, LTERM);
FreeGraph(agraph);
MPI_Comm_free(&newcomm);
MPI_Comm_free(&labelcomm);
IFSET(ctrl->dbglvl, DBG_TIME, stoptimer(ctrl->InitPartTmr));
}
/*************************************************************************
* This function assembles the graph into a single processor
**************************************************************************/
GraphType *AssembleMultisectedGraph(CtrlType *ctrl, GraphType *graph, WorkSpaceType *wspace)
{
int i, j, k, l, gnvtxs, nvtxs, gnedges, nedges, gsize;
idxtype *xadj, *vwgt, *where, *adjncy, *adjwgt, *vtxdist, *imap;
idxtype *axadj, *aadjncy, *aadjwgt, *avwgt, *awhere, *alabel;
idxtype *mygraph, *ggraph;
int *recvcounts, *displs, mysize;
GraphType *agraph;
gnvtxs = graph->gnvtxs;
nvtxs = graph->nvtxs;
nedges = graph->xadj[nvtxs];
xadj = graph->xadj;
vwgt = graph->vwgt;
where = graph->where;
adjncy = graph->adjncy;
adjwgt = graph->adjwgt;
vtxdist = graph->vtxdist;
imap = graph->imap;
/* Determine the # of idxtype to receive from each processor */
recvcounts = imalloc(ctrl->npes, "AssembleGraph: recvcounts");
mysize = 3*nvtxs + 2*nedges;
MPI_Allgather((void *)(&mysize), 1, MPI_INT, (void *)recvcounts, 1, MPI_INT, ctrl->comm);
displs = imalloc(ctrl->npes+1, "AssembleGraph: displs");
displs[0] = 0;
for (i=1; i<ctrl->npes+1; i++)
displs[i] = displs[i-1] + recvcounts[i-1];
/* Construct the one-array storage format of the assembled graph */
mygraph = (mysize <= wspace->maxcore ? wspace->core : idxmalloc(mysize, "AssembleGraph: mygraph"));
for (k=i=0; i<nvtxs; i++) {
mygraph[k++] = xadj[i+1]-xadj[i];
mygraph[k++] = vwgt[i];
mygraph[k++] = where[i];
for (j=xadj[i]; j<xadj[i+1]; j++) {
mygraph[k++] = imap[adjncy[j]];
mygraph[k++] = adjwgt[j];
}
}
ASSERT(ctrl, mysize == k);
/* Assemble the entire graph */
gsize = displs[ctrl->npes];
ggraph = (gsize <= wspace->maxcore-mysize ? wspace->core+mysize : idxmalloc(gsize, "AssembleGraph: ggraph"));
MPI_Allgatherv((void *)mygraph, mysize, IDX_DATATYPE, (void *)ggraph, recvcounts, displs, IDX_DATATYPE, ctrl->comm);
GKfree((void **)&recvcounts, (void **)&displs, LTERM);
if (mysize > wspace->maxcore)
free(mygraph);
agraph = CreateGraph();
agraph->nvtxs = gnvtxs;
agraph->nedges = gnedges = (gsize-3*gnvtxs)/2;
/* Allocate memory for the assembled graph */
axadj = agraph->xadj = idxmalloc(gnvtxs+1, "AssembleGraph: axadj");
avwgt = agraph->vwgt = idxmalloc(gnvtxs, "AssembleGraph: avwgt");
awhere = agraph->where = idxmalloc(gnvtxs, "AssembleGraph: awhere");
aadjncy = agraph->adjncy = idxmalloc(gnedges, "AssembleGraph: adjncy");
aadjwgt = agraph->adjwgt = idxmalloc(gnedges, "AssembleGraph: adjwgt");
alabel = agraph->label = idxmalloc(gnvtxs, "AssembleGraph: alabel");
for (k=j=i=0; i<gnvtxs; i++) {
axadj[i] = ggraph[k++];
avwgt[i] = ggraph[k++];
awhere[i] = ggraph[k++];
for (l=0; l<axadj[i]; l++) {
aadjncy[j] = ggraph[k++];
aadjwgt[j] = ggraph[k++];
j++;
}
}
/* Now fix up the received graph */
MAKECSR(i, gnvtxs, axadj);
for (i=0; i<gnvtxs; i++)
alabel[i] = i;
if (gsize > wspace->maxcore-mysize)
free(ggraph);
return agraph;
}