void LocalAggregationAlgorithm<LocalOrdinal, GlobalOrdinal, Node, LocalMatOps>::CoarsenUncoupled(GraphBase const & graph, Aggregates & aggregates) const {
Monitor m(*this, "Coarsen Uncoupled");
std::string orderingType;
switch(ordering_) {
case NATURAL:
orderingType="Natural";
break;
case RANDOM:
orderingType="Random";
break;
case GRAPH:
orderingType="Graph";
break;
default:
break;
}
GetOStream(Runtime1) << "Ordering: " << orderingType << std::endl;
GetOStream(Runtime1) << "Min nodes per aggregate: " << minNodesPerAggregate_ << std::endl;
GetOStream(Runtime1) << "Max nbrs already selected: " << maxNeighAlreadySelected_ << std::endl;
/* Create Aggregation object */
my_size_t nAggregates = 0;
/* ============================================================= */
/* aggStat indicates whether this node has been aggreated, and */
/* vertex2AggId stores the aggregate number where this node has */
/* been aggregated into. */
/* ============================================================= */
Teuchos::ArrayRCP<NodeState> aggStat;
const my_size_t nRows = graph.GetNodeNumVertices();
if (nRows > 0) aggStat = Teuchos::arcp<NodeState>(nRows);
for ( my_size_t i = 0; i < nRows; ++i ) aggStat[i] = READY;
/* ============================================================= */
/* Phase 1 : */
/* for all nodes, form a new aggregate with its neighbors */
/* if the number of its neighbors having been aggregated does */
/* not exceed a given threshold */
/* (GetMaxNeighAlreadySelected() = 0 ===> Vanek's scheme) */
/* ============================================================= */
/* some general variable declarations */
Teuchos::ArrayRCP<LO> randomVector;
RCP<MueLu::LinkedList> nodeList; /* list storing the next node to pick as a root point for ordering_ == GRAPH */
MueLu_SuperNode *aggHead=NULL, *aggCurrent=NULL, *supernode=NULL;
/**/
if ( ordering_ == RANDOM ) /* random ordering */
{
//TODO: could be stored in a class that respect interface of LinkedList
randomVector = Teuchos::arcp<LO>(nRows); //size_t or int ?-> to be propagated
for (my_size_t i = 0; i < nRows; ++i) randomVector[i] = i;
RandomReorder(randomVector);
}
else if ( ordering_ == GRAPH ) /* graph ordering */
{
nodeList = rcp(new MueLu::LinkedList());
nodeList->Add(0);
}
/* main loop */
{
LO iNode = 0;
LO iNode2 = 0;
Teuchos::ArrayRCP<LO> vertex2AggId = aggregates.GetVertex2AggId()->getDataNonConst(0); // output only: contents ignored
while (iNode2 < nRows)
{
/*------------------------------------------------------ */
/* pick the next node to aggregate */
/*------------------------------------------------------ */
if ( ordering_ == NATURAL ) iNode = iNode2++;
else if ( ordering_ == RANDOM ) iNode = randomVector[iNode2++];
else if ( ordering_ == GRAPH )
{
if ( nodeList->IsEmpty() )
{
for ( int jNode = 0; jNode < nRows; ++jNode )
{
if ( aggStat[jNode] == READY )
{
nodeList->Add(jNode); //TODO optim: not necessary to create a node. Can just set iNode value and skip the end
break;
}
}
}
if ( nodeList->IsEmpty() ) break; /* end of the while loop */ //TODO: coding style :(
iNode = nodeList->Pop();
}
else {
throw(Exceptions::RuntimeError("CoarsenUncoupled: bad aggregation ordering option"));
}
/*------------------------------------------------------ */
/* consider further only if the node is in READY mode */
/*------------------------------------------------------ */
if ( aggStat[iNode] == READY )
{
// neighOfINode is the neighbor node list of node 'iNode'.
Teuchos::ArrayView<const LO> neighOfINode = graph.getNeighborVertices(iNode);
typename Teuchos::ArrayView<const LO>::size_type length = neighOfINode.size();
supernode = new MueLu_SuperNode;
try {
supernode->list = Teuchos::arcp<int>(length+1);
} catch (std::bad_alloc&) {
TEUCHOS_TEST_FOR_EXCEPTION(true, Exceptions::RuntimeError, "MueLu::LocalAggregationAlgorithm::CoarsenUncoupled(): Error: couldn't allocate memory for supernode! length=" + Teuchos::toString(length));
}
supernode->maxLength = length;
supernode->length = 1;
supernode->list[0] = iNode;
int selectFlag = 1;
{
/*--------------------------------------------------- */
/* count the no. of neighbors having been aggregated */
/*--------------------------------------------------- */
int count = 0;
for (typename Teuchos::ArrayView<const LO>::const_iterator it = neighOfINode.begin(); it != neighOfINode.end(); ++it)
{
int index = *it;
if ( index < nRows )
{
if ( aggStat[index] == READY ||
aggStat[index] == NOTSEL )
supernode->list[supernode->length++] = index;
else count++;
}
}
/*--------------------------------------------------- */
/* if there are too many neighbors aggregated or the */
/* number of nodes in the new aggregate is too few, */
/* don't do this one */
/*--------------------------------------------------- */
if ( count > GetMaxNeighAlreadySelected() ) selectFlag = 0;
}
// Note: the supernode length is actually 1 more than the
// number of nodes in the candidate aggregate. The
// root is counted twice. I'm not sure if this is
// a bug or a feature ... so I'll leave it and change
// < to <= in the if just below.
if (selectFlag != 1 ||
supernode->length <= GetMinNodesPerAggregate())
{
aggStat[iNode] = NOTSEL;
delete supernode;
if ( ordering_ == GRAPH ) /* if graph ordering */
{
for (typename Teuchos::ArrayView<const LO>::const_iterator it = neighOfINode.begin(); it != neighOfINode.end(); ++it)
{
int index = *it;
if ( index < nRows && aggStat[index] == READY )
{
nodeList->Add(index);
}
}
}
}
else
{
aggregates.SetIsRoot(iNode);
for ( int j = 0; j < supernode->length; ++j )
{
int jNode = supernode->list[j];
aggStat[jNode] = SELECTED;
vertex2AggId[jNode] = nAggregates;
if ( ordering_ == GRAPH ) /* if graph ordering */
{
Teuchos::ArrayView<const LO> neighOfJNode = graph.getNeighborVertices(jNode);
for (typename Teuchos::ArrayView<const LO>::const_iterator it = neighOfJNode.begin(); it != neighOfJNode.end(); ++it)
{
int index = *it;
if ( index < nRows && aggStat[index] == READY )
{
nodeList->Add(index);
}
}
}
}
supernode->next = NULL;
supernode->index = nAggregates;
if ( nAggregates == 0 )
{
aggHead = supernode;
aggCurrent = supernode;
}
else
{
aggCurrent->next = supernode;
aggCurrent = supernode;
}
nAggregates++;
// unused aggCntArray[nAggregates] = supernode->length;
}
}
} // end of 'for'
// views on distributed vectors are freed here.
} // end of 'main loop'
nodeList = Teuchos::null;
/* Update aggregate object */
aggregates.SetNumAggregates(nAggregates);
/* Verbose */
{
const RCP<const Teuchos::Comm<int> > & comm = graph.GetComm();
if (IsPrint(Warnings0)) {
GO localReady=0, globalReady;
// Compute 'localReady'
for ( my_size_t i = 0; i < nRows; ++i )
if (aggStat[i] == READY) localReady++;
// Compute 'globalReady'
sumAll(comm, localReady, globalReady);
if(globalReady > 0)
GetOStream(Warnings0) << "Warning: " << globalReady << " READY nodes left" << std::endl;
}
if (IsPrint(Statistics1)) {
// Compute 'localSelected'
LO localSelected=0;
for ( my_size_t i = 0; i < nRows; ++i )
if ( aggStat[i] == SELECTED ) localSelected++;
// Compute 'globalSelected'
GO globalSelected; sumAll(comm, (GO)localSelected, globalSelected);
// Compute 'globalNRows'
GO globalNRows; sumAll(comm, (GO)nRows, globalNRows);
GetOStream(Statistics1) << "Nodes aggregated = " << globalSelected << " (" << globalNRows << ")" << std::endl;
}
if (IsPrint(Statistics1)) {
GO nAggregatesGlobal; sumAll(comm, (GO)nAggregates, nAggregatesGlobal);
GetOStream(Statistics1) << "Total aggregates = " << nAggregatesGlobal << std::endl;
}
} // verbose
/* ------------------------------------------------------------- */
/* clean up */
/* ------------------------------------------------------------- */
aggCurrent = aggHead;
while ( aggCurrent != NULL )
{
supernode = aggCurrent;
aggCurrent = aggCurrent->next;
delete supernode;
}
} // CoarsenUncoupled
