/*************************************************************************
* This function takes a bisection and constructs a minimum weight vertex
* separator out of it. It uses the node-based separator refinement for it.
**************************************************************************/
void ConstructSeparator(CtrlType *ctrl, GraphType *graph, float ubfactor)
{
int i, j, k, nvtxs, nbnd;
idxtype *xadj, *where, *bndind;
nvtxs = graph->nvtxs;
xadj = graph->xadj;
nbnd = graph->nbnd;
bndind = graph->bndind;
where = idxcopy(nvtxs, graph->where, idxwspacemalloc(ctrl, nvtxs));
/* Put the nodes in the boundary into the separator */
for (i=0; i<nbnd; i++) {
j = bndind[i];
if (xadj[j+1]-xadj[j] > 0) /* Ignore islands */
where[j] = 2;
}
GKfree(&graph->rdata, LTERM);
Allocate2WayNodePartitionMemory(ctrl, graph);
idxcopy(nvtxs, where, graph->where);
idxwspacefree(ctrl, nvtxs);
ASSERT(IsSeparable(graph));
Compute2WayNodePartitionParams(ctrl, graph);
ASSERT(CheckNodePartitionParams(graph));
FM_2WayNodeRefine(ctrl, graph, ubfactor, 8);
ASSERT(IsSeparable(graph));
}
/*************************************************************************
* This function is the entry point of the separator refinement
**************************************************************************/
void Refine2WayNode(CtrlType *ctrl, GraphType *orggraph, GraphType *graph, float ubfactor)
{
IFSET(ctrl->dbglvl, DBG_TIME, starttimer(ctrl->UncoarsenTmr));
for (;;) {
IFSET(ctrl->dbglvl, DBG_TIME, starttimer(ctrl->RefTmr));
if (ctrl->RType != 15)
FM_2WayNodeBalance(ctrl, graph, ubfactor);
switch (ctrl->RType) {
case 1:
FM_2WayNodeRefine(ctrl, graph, ubfactor, 8);
break;
case 2:
FM_2WayNodeRefine_OneSided(ctrl, graph, ubfactor, 8);
break;
case 3:
FM_2WayNodeRefine(ctrl, graph, ubfactor, 8);
FM_2WayNodeRefine_OneSided(ctrl, graph, ubfactor, 8);
break;
case 4:
FM_2WayNodeRefine_OneSided(ctrl, graph, ubfactor, 8);
FM_2WayNodeRefine(ctrl, graph, ubfactor, 8);
break;
case 5:
FM_2WayNodeRefineEqWgt(ctrl, graph, 8);
break;
}
IFSET(ctrl->dbglvl, DBG_TIME, stoptimer(ctrl->RefTmr));
if (graph == orggraph)
break;
graph = graph->finer;
IFSET(ctrl->dbglvl, DBG_TIME, starttimer(ctrl->ProjectTmr));
Project2WayNodePartition(ctrl, graph);
IFSET(ctrl->dbglvl, DBG_TIME, stoptimer(ctrl->ProjectTmr));
}
IFSET(ctrl->dbglvl, DBG_TIME, stoptimer(ctrl->UncoarsenTmr));
}
/*************************************************************************
* This function takes a graph and produces a bisection by using a region
* growing algorithm. The resulting partition is returned in
* graph->where
**************************************************************************/
void GrowBisectionNode(CtrlType *ctrl, GraphType *graph, float ubfactor)
{
int i, j, k, nvtxs, drain, nleft, first, last, pwgts[2], tpwgts[2], minpwgt[2], maxpwgt[2], from, bestcut, icut, mincut, me, pass, nbfs;
idxtype *xadj, *vwgt, *adjncy, *adjwgt, *where, *bndind;
idxtype *queue, *touched, *gain, *bestwhere;
nvtxs = graph->nvtxs;
xadj = graph->xadj;
vwgt = graph->vwgt;
adjncy = graph->adjncy;
adjwgt = graph->adjwgt;
bestwhere = idxmalloc(nvtxs, "BisectGraph: bestwhere");
queue = idxmalloc(nvtxs, "BisectGraph: queue");
touched = idxmalloc(nvtxs, "BisectGraph: touched");
tpwgts[0] = idxsum(nvtxs, vwgt);
tpwgts[1] = tpwgts[0]/2;
tpwgts[0] -= tpwgts[1];
maxpwgt[0] = ubfactor*tpwgts[0];
maxpwgt[1] = ubfactor*tpwgts[1];
minpwgt[0] = (1.0/ubfactor)*tpwgts[0];
minpwgt[1] = (1.0/ubfactor)*tpwgts[1];
/* Allocate memory for graph->rdata. Allocate sufficient memory for both edge and node */
graph->rdata = idxmalloc(5*nvtxs+3, "GrowBisectionNode: graph->rdata");
graph->pwgts = graph->rdata;
graph->where = graph->rdata + 3;
graph->bndptr = graph->rdata + nvtxs + 3;
graph->bndind = graph->rdata + 2*nvtxs + 3;
graph->nrinfo = (NRInfoType *)(graph->rdata + 3*nvtxs + 3);
graph->id = graph->rdata + 3*nvtxs + 3;
graph->ed = graph->rdata + 4*nvtxs + 3;
where = graph->where;
bndind = graph->bndind;
nbfs = (nvtxs <= ctrl->CoarsenTo ? SMALLNIPARTS : LARGENIPARTS);
bestcut = tpwgts[0]+tpwgts[1];
for (nbfs++; nbfs>0; nbfs--) {
idxset(nvtxs, 0, touched);
pwgts[1] = tpwgts[0]+tpwgts[1];
pwgts[0] = 0;
idxset(nvtxs, 1, where);
queue[0] = RandomInRange(nvtxs);
touched[queue[0]] = 1;
first = 0; last = 1;
nleft = nvtxs-1;
drain = 0;
/* Start the BFS from queue to get a partition */
if (nbfs >= 1) {
for (;;) {
if (first == last) { /* Empty. Disconnected graph! */
if (nleft == 0 || drain)
break;
k = RandomInRange(nleft);
for (i=0; i<nvtxs; i++) {
if (touched[i] == 0) {
if (k == 0)
break;
else
k--;
}
}
queue[0] = i;
touched[i] = 1;
first = 0; last = 1;;
nleft--;
}
i = queue[first++];
if (pwgts[1]-vwgt[i] < minpwgt[1]) {
drain = 1;
continue;
}
where[i] = 0;
INC_DEC(pwgts[0], pwgts[1], vwgt[i]);
if (pwgts[1] <= maxpwgt[1])
break;
drain = 0;
for (j=xadj[i]; j<xadj[i+1]; j++) {
k = adjncy[j];
if (touched[k] == 0) {
queue[last++] = k;
touched[k] = 1;
nleft--;
}
}
}
}
/*************************************************************
* Do some partition refinement
**************************************************************/
Compute2WayPartitionParams(ctrl, graph);
Balance2Way(ctrl, graph, tpwgts, ubfactor);
FM_2WayEdgeRefine(ctrl, graph, tpwgts, 4);
/* Construct and refine the vertex separator */
for (i=0; i<graph->nbnd; i++)
where[bndind[i]] = 2;
Compute2WayNodePartitionParams(ctrl, graph);
FM_2WayNodeRefine(ctrl, graph, ubfactor, 6);
/* printf("ISep: [%d %d %d] %d\n", graph->pwgts[0], graph->pwgts[1], graph->pwgts[2], bestcut); */
if (bestcut > graph->mincut) {
bestcut = graph->mincut;
idxcopy(nvtxs, where, bestwhere);
}
}
graph->mincut = bestcut;
idxcopy(nvtxs, bestwhere, where);
Compute2WayNodePartitionParams(ctrl, graph);
GKfree(&bestwhere, &queue, &touched, LTERM);
}
