-// Copyright (C) 2007-2015 CEA/DEN, EDF R&D
+// Copyright (C) 2007-2024 CEA, EDF
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
using namespace std;
-namespace ParaMEDMEM
+namespace MEDCoupling
{
const int OverlapElementLocator::START_TAG_MESH_XCH = 1140;
OverlapElementLocator::OverlapElementLocator(const ParaFIELD *sourceField, const ParaFIELD *targetField,
- const ProcessorGroup& group, double epsAbs)
+ const ProcessorGroup& group, double epsAbs, int workSharingAlgo)
: _local_source_field(sourceField),
_local_target_field(targetField),
_local_source_mesh(0),
_local_target_mesh(0),
_domain_bounding_boxes(0),
- _group(group),
- _epsAbs(epsAbs)
+ _epsAbs(epsAbs),
+ _group(group)
{
if(_local_source_field)
_local_source_mesh=_local_source_field->getSupport()->getCellMesh();
if(_local_target_field)
_local_target_mesh=_local_target_field->getSupport()->getCellMesh();
_comm=getCommunicator();
- computeBoundingBoxesAndTodoList();
+
+ computeBoundingBoxesAndInteractionList();
+ switch(workSharingAlgo)
+ {
+ case 0:
+ computeTodoList_original(); break;
+ case 1:
+ computeTodoList_new(false); break;
+ case 2:
+ computeTodoList_new(true); break;
+ default:
+ throw INTERP_KERNEL::Exception("OverlapElementLocator::OverlapElementLocator(): invalid algorithm selected!");
+ }
+
+ fillProcToSend();
}
OverlapElementLocator::~OverlapElementLocator()
return group->getComm();
}
- void OverlapElementLocator::computeBoundingBoxesAndTodoList()
+ void OverlapElementLocator::computeBoundingBoxesAndInteractionList()
{
CommInterface comm_interface=_group.getCommInterface();
const MPIProcessorGroup* group=static_cast<const MPIProcessorGroup*> (&_group);
_domain_bounding_boxes,bbSize, MPI_DOUBLE,
*comm);
- // Computation of all pairs needing an interpolation pairs are duplicated now !
-
+ // Computation of all pairs needing an interpolation - pairs are duplicated now !
_proc_pairs.clear();//first is source second is target
_proc_pairs.resize(_group.size());
for(int i=0;i<_group.size();i++)
for(int j=0;j<_group.size();j++)
- {
- if(intersectsBoundingBox(i,j))
- {
- _proc_pairs[i].push_back(j);
-// std::cout << "(" << _group.myRank() << ") PROC pair: " << i << "," << j << std::endl;
- }
- }
+ if(intersectsBoundingBox(i,j))
+ _proc_pairs[i].push_back(j);
+ }
+
+ /*! See main OverlapDEC documentation for an explanation on this one. This is the original work sharing algorithm.
+ */
+ void OverlapElementLocator::computeTodoList_original()
+ {
// OK now let's assigning as balanced as possible, job to each proc of group
- std::vector< std::vector< ProcCouple > > pairsToBeDonePerProc(_group.size());
- int i=0;
- for(std::vector< std::vector< int > >::const_iterator it1=_proc_pairs.begin();it1!=_proc_pairs.end();it1++,i++)
- for(std::vector< int >::const_iterator it2=(*it1).begin();it2!=(*it1).end();it2++)
+ _all_todo_lists.resize(_group.size());
+ for(int i = 0; i < _group.size(); i++)
+ for(const int j: _proc_pairs[i])
{
- if(pairsToBeDonePerProc[i].size()<=pairsToBeDonePerProc[*it2].size())//it includes the fact that i==*it2
- pairsToBeDonePerProc[i].push_back(ProcCouple(i,*it2));
+ if(_all_todo_lists[i].size()<=_all_todo_lists[j].size())//it includes the fact that i==j
+ _all_todo_lists[i].push_back(ProcCouple(i,j));
else
- pairsToBeDonePerProc[*it2].push_back(ProcCouple(i,*it2));
+ _all_todo_lists[j].push_back(ProcCouple(i,j));
}
//Keeping todo list of current proc. _to_do_list contains a set of pair where at least _group.myRank() appears once.
//This proc will be in charge to perform interpolation of any of element of '_to_do_list'
//If _group.myRank()==myPair.first, current proc should fetch target mesh of myPair.second (if different from _group.myRank()).
//If _group.myRank()==myPair.second, current proc should fetch source mesh of myPair.second.
-
+
int myProcId=_group.myRank();
- _to_do_list=pairsToBeDonePerProc[myProcId];
+ _to_do_list=_all_todo_lists[myProcId];
-// std::stringstream scout;
-// scout << "(" << myProcId << ") my TODO list is: ";
-// for (std::vector< ProcCouple >::const_iterator itdbg=_to_do_list.begin(); itdbg!=_to_do_list.end(); itdbg++)
-// scout << "(" << (*itdbg).first << "," << (*itdbg).second << ")";
-// std::cout << scout.str() << "\n";
+#ifdef DEC_DEBUG
+ std::stringstream scout;
+ scout << "(" << myProcId << ") my TODO list is: ";
+ for (const ProcCouple& pc: _to_do_list)
+ scout << "(" << pc.first << "," << pc.second << ")";
+ std::cout << scout.str() << "\n";
+#endif
+ }
+ /*! More efficient (?) work sharing algorithm: a job (i,j) is initially assigned twice: to proc#i and to proc#j.
+ * Then try to reduce as much as possible the variance of the num of jobs per proc by selecting the right duplicate
+ * to remove:
+ * - take the most loaded proc i,
+ * + select the job (i,j) for which proc#j is the less loaded
+ * + remove this job from proc#i, and mark it as 'unremovable' from proc#j
+ * - repeat until no more duplicates are found
+ */
+ void OverlapElementLocator::computeTodoList_new(bool revertIter)
+ {
+ using namespace std;
+ int infinity = std::numeric_limits<int>::max();
+
+ //
+ // Initialisation
+ //
+ int grp_size = _group.size();
+ // For each proc, a map giving for a job (=an interaction (i,j)) its 'load', i.e. the amount of work found on proc #j
+ vector < map<ProcCouple, int> > full_set(grp_size );
+ for(int srcProcID = 0; srcProcID < _group.size(); srcProcID++)
+ for(const int tgtProcID: _proc_pairs[srcProcID])
+ {
+ // Here a pair of the form (i,i) is added only once!
+ ProcCouple cpl = make_pair(srcProcID, tgtProcID);
+ // The interaction (i,j) is initially given to both procs #i and #j - load is initialised at -1:
+ full_set[srcProcID][cpl] = -1;
+ full_set[tgtProcID][cpl] = -1;
+ }
+ // Compute load:
+ int procID = 0;
+ for(auto& itVector : full_set)
+ {
+ for (auto &mapIt : itVector)
+ {
+ const ProcCouple & cpl = mapIt.first;
+ if (cpl.first == cpl.second) // interaction (i,i) : can not be removed:
+ // special case - this couple can not be removed in the future
+ mapIt.second = infinity;
+ else
+ {
+ if(cpl.first == procID)
+ mapIt.second = (int)full_set[cpl.second].size();
+ else // cpl.second == srcProcID
+ mapIt.second = (int)full_set[cpl.first].size();
+ }
+ }
+ procID++;
+ }
+ INTERP_KERNEL::AutoPtr<bool> proc_valid = new bool[grp_size];
+ fill((bool *)proc_valid, proc_valid+grp_size, true);
+
+ //
+ // Now the algo:
+ //
+ while (find((bool *)proc_valid, proc_valid+grp_size, true) != proc_valid+grp_size) // as long as proc_valid is not full of 'false'
+ {
+ // Most loaded proc:
+ int max_sz = -1, max_id = -1;
+ int procID = 0;
+ for(const auto& a_set: full_set)
+ {
+ int sz = (int)a_set.size();
+ if (proc_valid[procID] && sz > max_sz)
+ {
+ max_sz = sz;
+ max_id = procID;
+ }
+ procID++;
+ }
+
+ // Nothing more to do:
+ if (max_sz == -1) break;
+ // For this proc, job with less loaded second proc:
+ int min_sz = infinity;
+ map<ProcCouple, int> & max_map = full_set[max_id];
+ ProcCouple hit_cpl = make_pair(-1,-1);
+ if(revertIter)
+ {
+ // Use a reverse iterator here increases our chances to hit a couple of the form (i, myProcId)
+ // meaning that the final matrix computed won't have to be sent: save some comm.
+ for(auto ritMap=max_map.rbegin(); ritMap != max_map.rend(); ritMap++)
+ if ((*ritMap).second < min_sz)
+ {
+ hit_cpl = (*ritMap).first;
+ min_sz = (*ritMap).second;
+ }
+ }
+ else
+ {
+ for(const auto& mapIt : max_map)
+ if (mapIt.second < min_sz)
+ {
+ hit_cpl = mapIt.first;
+ min_sz = mapIt.second;
+ }
+ }
+ if (hit_cpl.first == -1)
+ {
+ // Plouf. Current proc 'max_id' can not be reduced. Invalid it and move next:
+ proc_valid[max_id] = false;
+ continue;
+ }
+ // Remove item from proc 'max_id'
+ full_set[max_id].erase(hit_cpl);
+ // And mark it as not removable on the other side:
+ if (hit_cpl.first == max_id)
+ full_set[hit_cpl.second][hit_cpl] = infinity;
+ else // hit_cpl.second == max_id
+ full_set[hit_cpl.first][hit_cpl] = infinity;
+
+ // Now update all counts of valid maps:
+ procID = 0;
+ for(auto& itVector: full_set)
+ {
+ if(proc_valid[procID] && procID != max_id)
+ for(auto& mapIt: itVector)
+ {
+ const ProcCouple & cpl = mapIt.first;
+ if (mapIt.second == infinity) // Unremovable item:
+ continue;
+ if (cpl.first == max_id || cpl.second == max_id)
+ mapIt.second--;
+ }
+ procID++;
+ }
+ }
+
+ //
+ // Final formatting - extract remaining keys in each map:
+ //
+ int myProcId = _group.myRank();
+ _all_todo_lists.resize(grp_size);
+ procID = 0;
+ for(const auto& itVector: full_set)
+ {
+ for(const auto& mapIt: itVector)
+ _all_todo_lists[procID].push_back(mapIt.first);
+ procID++;
+ }
+ _to_do_list=_all_todo_lists[myProcId];
+
+#ifdef DEC_DEBUG
+ std::stringstream scout;
+ scout << "(" << myProcId << ") my TODO list is: ";
+ for (const ProcCouple& pc: _to_do_list)
+ scout << "(" << pc.first << "," << pc.second << ")";
+ std::cout << scout.str() << "\n";
+#endif
+ }
+
+ void OverlapElementLocator::debugPrintWorkSharing(std::ostream & ostr) const
+ {
+ std::vector< std::vector< ProcCouple > >::const_iterator it = _all_todo_lists.begin();
+ ostr << "TODO list lengths: ";
+ for(; it != _all_todo_lists.end(); ++it)
+ ostr << (*it).size() << " ";
+ ostr << "\n";
+ }
+
+ void OverlapElementLocator::fillProcToSend()
+ {
// Feeding now '_procs_to_send*'. A same id can appears twice. The second parameter in pair means what
// to send true=source, false=target
+ int myProcId=_group.myRank();
_procs_to_send_mesh.clear();
_procs_to_send_field.clear();
- for(int i=_group.size()-1;i>=0;i--)
+ for(int i=0;i<_group.size();i++)
{
- const std::vector< ProcCouple >& anRemoteProcToDoList=pairsToBeDonePerProc[i];
- for(std::vector< ProcCouple >::const_iterator it=anRemoteProcToDoList.begin();it!=anRemoteProcToDoList.end();it++)
+ for(const ProcCouple& pc: _all_todo_lists[i])
{
- if((*it).first==myProcId)
+ if(pc.first==myProcId)
{
if(i!=myProcId)
_procs_to_send_mesh.push_back(Proc_SrcOrTgt(i,true));
- _procs_to_send_field.push_back((*it).second);
+ _procs_to_send_field.push_back(pc.second);
}
- if((*it).second==myProcId)
+ if(pc.second==myProcId)
if(i!=myProcId)
_procs_to_send_mesh.push_back(Proc_SrcOrTgt(i,false));
}
}
+ // Sort to avoid deadlocks!!
+ std::sort(_procs_to_send_mesh.begin(), _procs_to_send_mesh.end());
+#ifdef DEC_DEBUG
+ std::stringstream scout;
+ scout << "(" << _group.myRank() << ") PROC TO SEND list is: ";
+ for (const auto& pc: _procs_to_send_mesh)
+ scout << "(" << pc.first << "," << (pc.second ? "src":"tgt") << ") ";
+ std::cout << scout.str() << "\n";
+#endif
}
+
/*!
* The aim of this method is to perform the communication to get data corresponding to '_to_do_list' attribute.
* The principle is the following : if proc n1 and n2 need to perform a cross sending with n1<n2, then n1 will send first and receive then.
{
int myProcId=_group.myRank();
//starting to receive every procs whose id is lower than myProcId.
- std::vector< ProcCouple > toDoListForFetchRemaining;
- for(std::vector< ProcCouple >::const_iterator it=_to_do_list.begin();it!=_to_do_list.end();it++)
+ std::vector<Proc_SrcOrTgt> firstRcv, secondRcv;
+ for (const ProcCouple& pc: _to_do_list)
{
- int first = (*it).first, second = (*it).second;
- if(first!=second)
+ if(pc.first == pc.second) continue; // no xchg needed
+
+ if(pc.first==myProcId)
{
- if(first==myProcId)
- {
- if(second<myProcId)
- receiveRemoteMeshFrom(second,false);
- else
- toDoListForFetchRemaining.push_back(ProcCouple(first,second));
- }
- else
- {//(*it).second==myProcId
- if(first<myProcId)
- receiveRemoteMeshFrom(first,true);
- else
- toDoListForFetchRemaining.push_back(ProcCouple(first,second));
- }
+ if(pc.second<myProcId) firstRcv.push_back(Proc_SrcOrTgt(pc.second,false));
+ else secondRcv.push_back(Proc_SrcOrTgt(pc.second, false));
}
- }
- //sending source or target mesh to remote procs
- for(std::vector< Proc_SrcOrTgt >::const_iterator it2=_procs_to_send_mesh.begin();it2!=_procs_to_send_mesh.end();it2++)
- sendLocalMeshTo((*it2).first,(*it2).second,matrix);
- //fetching remaining meshes
- for(std::vector< ProcCouple >::const_iterator it=toDoListForFetchRemaining.begin();it!=toDoListForFetchRemaining.end();it++)
- {
- if((*it).first!=(*it).second)
- {
- if((*it).first==myProcId)
- receiveRemoteMeshFrom((*it).second,false);
- else//(*it).second==myProcId
- receiveRemoteMeshFrom((*it).first,true);
+ else
+ {//pc.second==myProcId
+ if(pc.first<myProcId) firstRcv.push_back(Proc_SrcOrTgt(pc.first,true));
+ else secondRcv.push_back(Proc_SrcOrTgt(pc.first,true));
}
}
+ // Actual receiving, in order please to avoid deadlocks!
+ std::sort(firstRcv.begin(), firstRcv.end());
+ for (const Proc_SrcOrTgt& pst: firstRcv)
+ receiveRemoteMeshFrom(pst.first, pst.second);
+
+ // Sending source or target mesh to remote procs (_procs_to_send_mesh is sorted too!)
+ for (const Proc_SrcOrTgt& pst: _procs_to_send_mesh)
+ sendLocalMeshTo(pst.first, pst.second,matrix);
+
+ // Actual 2nd receiving, in order again please to avoid deadlocks!
+ std::sort(secondRcv.begin(), secondRcv.end());
+ for (const Proc_SrcOrTgt& pst: secondRcv)
+ receiveRemoteMeshFrom(pst.first, pst.second);
}
std::string OverlapElementLocator::getSourceMethod() const
return (*it).second;
}
- const DataArrayInt *OverlapElementLocator::getSourceIds(int procId) const
+ const DataArrayIdType *OverlapElementLocator::getSourceIds(int procId) const
{
int myProcId=_group.myRank();
if(myProcId==procId)
return (*it).second;
}
- const DataArrayInt *OverlapElementLocator::getTargetIds(int procId) const
+ const DataArrayIdType *OverlapElementLocator::getTargetIds(int procId) const
{
int myProcId=_group.myRank();
if(myProcId==procId)
return (*it).second;
}
+ bool OverlapElementLocator::isInMyTodoList(int i, int j) const
+ {
+ ProcCouple cpl = std::make_pair(i, j);
+ return std::find(_to_do_list.begin(), _to_do_list.end(), cpl)!=_to_do_list.end();
+ }
bool OverlapElementLocator::intersectsBoundingBox(int isource, int itarget) const
{
*/
void OverlapElementLocator::sendLocalMeshTo(int procId, bool sourceOrTarget, OverlapInterpolationMatrix& matrix) const
{
+#ifdef DEC_DEBUG
+ int rank = _group.myRank();
+ std::string st = sourceOrTarget ? "src" : "tgt";
+ std::stringstream scout;
+ scout << "(" << rank << ") SEND part of " << st << " TO: " << procId;
+ std::cout << scout.str() << "\n";
+#endif
+
//int myProcId=_group.myRank();
const double *distant_bb=0;
MEDCouplingPointSet *local_mesh=0;
field=_local_target_field;
}
AutoDAInt elems=local_mesh->getCellsInBoundingBox(distant_bb,getBoundingBoxAdjustment());
- DataArrayInt *old2new_map;
+ DataArrayIdType *old2new_map;
MEDCouplingPointSet *send_mesh=static_cast<MEDCouplingPointSet *>(field->getField()->buildSubMeshData(elems->begin(),elems->end(),old2new_map));
if(sourceOrTarget)
matrix.keepTracksOfSourceIds(procId,old2new_map);
}
/*!
- * This method recieves source remote mesh on proc 'procId' if sourceOrTarget==True
- * This method recieves target remote mesh on proc 'procId' if sourceOrTarget==False
+ * This method receives source remote mesh on proc 'procId' if sourceOrTarget==True
+ * This method receives target remote mesh on proc 'procId' if sourceOrTarget==False
*/
void OverlapElementLocator::receiveRemoteMeshFrom(int procId, bool sourceOrTarget)
{
- DataArrayInt *old2new_map=0;
+#ifdef DEC_DEBUG
+ int rank = _group.myRank();
+ std::string st = sourceOrTarget ? "src" : "tgt";
+ std::stringstream scout;
+ scout << "(" << rank << ") RCV part of " << st << " FROM: " << procId;
+ std::cout << scout.str() << "\n";
+#endif
+ DataArrayIdType *old2new_map=0;
MEDCouplingPointSet *m=0;
receiveMesh(procId,m,old2new_map);
Proc_SrcOrTgt p(procId,sourceOrTarget);
_remote_elems[p]=old2new_map;
}
- void OverlapElementLocator::sendMesh(int procId, const MEDCouplingPointSet *mesh, const DataArrayInt *idsToSend) const
+ void OverlapElementLocator::sendMesh(int procId, const MEDCouplingPointSet *mesh, const DataArrayIdType *idsToSend) const
{
CommInterface comInterface=_group.getCommInterface();
// First stage : exchanging sizes
vector<double> tinyInfoLocalD;//tinyInfoLocalD not used for the moment
- vector<int> tinyInfoLocal;
+ vector<mcIdType> tinyInfoLocal;
vector<string> tinyInfoLocalS;
mesh->getTinySerializationInformation(tinyInfoLocalD,tinyInfoLocal,tinyInfoLocalS);
const MPI_Comm *comm=getCommunicator();
//
- int lgth[2];
- lgth[0]=tinyInfoLocal.size();
+ mcIdType lgth[2];
+ lgth[0]=ToIdType(tinyInfoLocal.size());
lgth[1]=idsToSend->getNbOfElems();
- comInterface.send(&lgth,2,MPI_INT,procId,START_TAG_MESH_XCH,*_comm);
- comInterface.send(&tinyInfoLocal[0],tinyInfoLocal.size(),MPI_INT,procId,START_TAG_MESH_XCH+1,*comm);
+ comInterface.send(&lgth,2,MPI_ID_TYPE,procId,START_TAG_MESH_XCH,*_comm);
+ comInterface.send(&tinyInfoLocal[0],(int)tinyInfoLocal.size(),MPI_ID_TYPE,procId,START_TAG_MESH_XCH+1,*comm);
//
- DataArrayInt *v1Local=0;
+ DataArrayIdType *v1Local=0;
DataArrayDouble *v2Local=0;
mesh->serialize(v1Local,v2Local);
- comInterface.send(v1Local->getPointer(),v1Local->getNbOfElems(),MPI_INT,procId,START_TAG_MESH_XCH+2,*comm);
- comInterface.send(v2Local->getPointer(),v2Local->getNbOfElems(),MPI_DOUBLE,procId,START_TAG_MESH_XCH+3,*comm);
+ comInterface.send(v1Local->getPointer(),(int)v1Local->getNbOfElems(),MPI_ID_TYPE,procId,START_TAG_MESH_XCH+2,*comm);
+ comInterface.send(v2Local->getPointer(),(int)v2Local->getNbOfElems(),MPI_DOUBLE,procId,START_TAG_MESH_XCH+3,*comm);
//finished for mesh, ids now
- comInterface.send(const_cast<int *>(idsToSend->getConstPointer()),lgth[1],MPI_INT,procId,START_TAG_MESH_XCH+4,*comm);
+ comInterface.send(const_cast<mcIdType *>(idsToSend->getConstPointer()),(int)lgth[1],MPI_ID_TYPE,procId,START_TAG_MESH_XCH+4,*comm);
//
v1Local->decrRef();
v2Local->decrRef();
}
- void OverlapElementLocator::receiveMesh(int procId, MEDCouplingPointSet* &mesh, DataArrayInt *&ids) const
+ void OverlapElementLocator::receiveMesh(int procId, MEDCouplingPointSet* &mesh, DataArrayIdType *&ids) const
{
- int lgth[2];
+ mcIdType lgth[2];
MPI_Status status;
const MPI_Comm *comm=getCommunicator();
CommInterface comInterface=_group.getCommInterface();
- comInterface.recv(lgth,2,MPI_INT,procId,START_TAG_MESH_XCH,*_comm,&status);
- std::vector<int> tinyInfoDistant(lgth[0]);
- ids=DataArrayInt::New();
+ comInterface.recv(lgth,2,MPI_ID_TYPE,procId,START_TAG_MESH_XCH,*_comm,&status);
+ std::vector<mcIdType> tinyInfoDistant(lgth[0]);
+ ids=DataArrayIdType::New();
ids->alloc(lgth[1],1);
- comInterface.recv(&tinyInfoDistant[0],lgth[0],MPI_INT,procId,START_TAG_MESH_XCH+1,*comm,&status);
+ comInterface.recv(&tinyInfoDistant[0],(int)lgth[0],MPI_ID_TYPE,procId,START_TAG_MESH_XCH+1,*comm,&status);
mesh=MEDCouplingPointSet::BuildInstanceFromMeshType((MEDCouplingMeshType)tinyInfoDistant[0]);
std::vector<std::string> unusedTinyDistantSts;
vector<double> tinyInfoDistantD(1);//tinyInfoDistantD not used for the moment
- DataArrayInt *v1Distant=DataArrayInt::New();
+ DataArrayIdType *v1Distant=DataArrayIdType::New();
DataArrayDouble *v2Distant=DataArrayDouble::New();
mesh->resizeForUnserialization(tinyInfoDistant,v1Distant,v2Distant,unusedTinyDistantSts);
- comInterface.recv(v1Distant->getPointer(),v1Distant->getNbOfElems(),MPI_INT,procId,START_TAG_MESH_XCH+2,*comm,&status);
- comInterface.recv(v2Distant->getPointer(),v2Distant->getNbOfElems(),MPI_DOUBLE,procId,START_TAG_MESH_XCH+3,*comm,&status);
+ comInterface.recv(v1Distant->getPointer(),(int)v1Distant->getNbOfElems(),MPI_ID_TYPE,procId,START_TAG_MESH_XCH+2,*comm,&status);
+ comInterface.recv(v2Distant->getPointer(),(int)v2Distant->getNbOfElems(),MPI_DOUBLE,procId,START_TAG_MESH_XCH+3,*comm,&status);
mesh->unserialization(tinyInfoDistantD,tinyInfoDistant,v1Distant,v2Distant,unusedTinyDistantSts);
//finished for mesh, ids now
- comInterface.recv(ids->getPointer(),lgth[1],MPI_INT,procId,1144,*comm,&status);
+ comInterface.recv(ids->getPointer(),(int)lgth[1],MPI_ID_TYPE,procId,1144,*comm,&status);
//
v1Distant->decrRef();
v2Distant->decrRef();