PetscErrorCode MatPartitioningSetFromOptions_Parmetis(PetscOptionItems *PetscOptionsObject,MatPartitioning part)
{
PetscErrorCode ierr;
PetscBool flag = PETSC_FALSE;
PetscFunctionBegin;
ierr = PetscOptionsHead(PetscOptionsObject,"Set ParMeTiS partitioning options");CHKERRQ(ierr);
ierr = PetscOptionsBool("-mat_partitioning_parmetis_coarse_sequential","Use sequential coarse partitioner","MatPartitioningParmetisSetCoarseSequential",flag,&flag,NULL);CHKERRQ(ierr);
if (flag) {
ierr = MatPartitioningParmetisSetCoarseSequential(part);CHKERRQ(ierr);
}
ierr = PetscOptionsBool("-mat_partitioning_parmetis_repartition","","MatPartitioningParmetisSetRepartition",flag,&flag,NULL);CHKERRQ(ierr);
if(flag){
ierr = MatPartitioningParmetisSetRepartition(part);CHKERRQ(ierr);
}
ierr = PetscOptionsTail();CHKERRQ(ierr);
PetscFunctionReturn(0);
}
/*
* Increase overlap for the sub-matrix across sub communicator
* sub-matrix could be a graph or numerical matrix
* */
PetscErrorCode MatIncreaseOverlapSplit_Single(Mat mat,IS *is,PetscInt ov)
{
PetscInt i,nindx,*indices_sc,*indices_ov,localsize,*localsizes_sc,localsize_tmp;
PetscInt *indices_ov_rd,nroots,nleaves,*localoffsets,*indices_recv,*sources_sc,*sources_sc_rd;
const PetscInt *indices;
PetscMPIInt srank,ssize,issamecomm,k,grank;
IS is_sc,allis_sc,partitioning;
MPI_Comm gcomm,dcomm,scomm;
PetscSF sf;
PetscSFNode *remote;
Mat *smat;
MatPartitioning part;
PetscErrorCode ierr;
PetscFunctionBegin;
/* get a sub communicator before call individual MatIncreaseOverlap
* since the sub communicator may be changed.
* */
ierr = PetscObjectGetComm((PetscObject)(*is),&dcomm);CHKERRQ(ierr);
/*make a copy before the original one is deleted*/
ierr = PetscCommDuplicate(dcomm,&scomm,NULL);CHKERRQ(ierr);
/*get a global communicator, where mat should be a global matrix */
ierr = PetscObjectGetComm((PetscObject)mat,&gcomm);CHKERRQ(ierr);
/*increase overlap on each individual subdomain*/
ierr = (*mat->ops->increaseoverlap)(mat,1,is,ov);CHKERRQ(ierr);
/*compare communicators */
ierr = MPI_Comm_compare(gcomm,scomm,&issamecomm);CHKERRQ(ierr);
/* if the sub-communicator is the same as the global communicator,
* user does not want to use a sub-communicator
* */
if(issamecomm == MPI_IDENT || issamecomm == MPI_CONGRUENT) PetscFunctionReturn(0);
/* if the sub-communicator is petsc_comm_self,
* user also does not care the sub-communicator
* */
ierr = MPI_Comm_compare(scomm,PETSC_COMM_SELF,&issamecomm);CHKERRQ(ierr);
if(issamecomm == MPI_IDENT || issamecomm == MPI_CONGRUENT){PetscFunctionReturn(0);}
/*local rank, size in a sub-communicator */
ierr = MPI_Comm_rank(scomm,&srank);CHKERRQ(ierr);
ierr = MPI_Comm_size(scomm,&ssize);CHKERRQ(ierr);
ierr = MPI_Comm_rank(gcomm,&grank);CHKERRQ(ierr);
/*create a new IS based on sub-communicator
* since the old IS is often based on petsc_comm_self
* */
ierr = ISGetLocalSize(*is,&nindx);CHKERRQ(ierr);
ierr = PetscCalloc1(nindx,&indices_sc);CHKERRQ(ierr);
ierr = ISGetIndices(*is,&indices);CHKERRQ(ierr);
ierr = PetscMemcpy(indices_sc,indices,sizeof(PetscInt)*nindx);CHKERRQ(ierr);
ierr = ISRestoreIndices(*is,&indices);CHKERRQ(ierr);
/*we do not need any more*/
ierr = ISDestroy(is);CHKERRQ(ierr);
/*create a index set based on the sub communicator */
ierr = ISCreateGeneral(scomm,nindx,indices_sc,PETSC_OWN_POINTER,&is_sc);CHKERRQ(ierr);
/*gather all indices within the sub communicator*/
ierr = ISAllGather(is_sc,&allis_sc);CHKERRQ(ierr);
ierr = ISDestroy(&is_sc);CHKERRQ(ierr);
/* gather local sizes */
ierr = PetscMalloc1(ssize,&localsizes_sc);CHKERRQ(ierr);
/*get individual local sizes for all index sets*/
ierr = MPI_Gather(&nindx,1,MPIU_INT,localsizes_sc,1,MPIU_INT,0,scomm);CHKERRQ(ierr);
/*only root does these computations */
if(!srank){
/*get local size for the big index set*/
ierr = ISGetLocalSize(allis_sc,&localsize);CHKERRQ(ierr);
ierr = PetscCalloc2(localsize,&indices_ov,localsize,&sources_sc);CHKERRQ(ierr);
ierr = PetscCalloc2(localsize,&indices_ov_rd,localsize,&sources_sc_rd);CHKERRQ(ierr);
ierr = ISGetIndices(allis_sc,&indices);CHKERRQ(ierr);
ierr = PetscMemcpy(indices_ov,indices,sizeof(PetscInt)*localsize);CHKERRQ(ierr);
ierr = ISRestoreIndices(allis_sc,&indices);CHKERRQ(ierr);
/*we do not need it any more */
ierr = ISDestroy(&allis_sc);CHKERRQ(ierr);
/*assign corresponding sources */
localsize_tmp = 0;
for(k=0; k<ssize; k++){
for(i=0; i<localsizes_sc[k]; i++){
sources_sc[localsize_tmp++] = k;
}
}
/*record where indices come from */
ierr = PetscSortIntWithArray(localsize,indices_ov,sources_sc);CHKERRQ(ierr);
/*count local sizes for reduced indices */
ierr = PetscMemzero(localsizes_sc,sizeof(PetscInt)*ssize);CHKERRQ(ierr);
/*initialize the first entity*/
if(localsize){
indices_ov_rd[0] = indices_ov[0];
sources_sc_rd[0] = sources_sc[0];
localsizes_sc[sources_sc[0]]++;
}
localsize_tmp = 1;
/*remove duplicate integers */
for(i=1; i<localsize; i++){
if(indices_ov[i] != indices_ov[i-1]){
indices_ov_rd[localsize_tmp] = indices_ov[i];
sources_sc_rd[localsize_tmp++] = sources_sc[i];
localsizes_sc[sources_sc[i]]++;
}
}
ierr = PetscFree2(indices_ov,sources_sc);CHKERRQ(ierr);
ierr = PetscCalloc1(ssize+1,&localoffsets);CHKERRQ(ierr);
for(k=0; k<ssize; k++){
localoffsets[k+1] = localoffsets[k] + localsizes_sc[k];
}
/*construct a star forest to send data back */
nleaves = localoffsets[ssize];
ierr = PetscMemzero(localoffsets,(ssize+1)*sizeof(PetscInt));CHKERRQ(ierr);
nroots = localsizes_sc[srank];
ierr = PetscCalloc1(nleaves,&remote);CHKERRQ(ierr);
for(i=0; i<nleaves; i++){
remote[i].rank = sources_sc_rd[i];
remote[i].index = localoffsets[sources_sc_rd[i]]++;
}
ierr = PetscFree(localoffsets);CHKERRQ(ierr);
}else{
ierr = ISDestroy(&allis_sc);CHKERRQ(ierr);
/*Allocate a 'zero' pointer */
ierr = PetscCalloc1(0,&remote);CHKERRQ(ierr);
nleaves = 0;
indices_ov_rd = 0;
sources_sc_rd = 0;
}
/*scatter sizes to everybody */
ierr = MPI_Scatter(localsizes_sc,1, MPIU_INT,&nroots,1, MPIU_INT,0,scomm);CHKERRQ(ierr);
/*free memory */
ierr = PetscFree(localsizes_sc);CHKERRQ(ierr);
ierr = PetscCalloc1(nroots,&indices_recv);CHKERRQ(ierr);
/*ierr = MPI_Comm_dup(scomm,&dcomm);CHKERRQ(ierr);*/
/*set data back to every body */
ierr = PetscSFCreate(scomm,&sf);CHKERRQ(ierr);
ierr = PetscSFSetType(sf,PETSCSFBASIC);CHKERRQ(ierr);
ierr = PetscSFSetFromOptions(sf);CHKERRQ(ierr);
ierr = PetscSFSetGraph(sf,nroots,nleaves,PETSC_NULL,PETSC_OWN_POINTER,remote,PETSC_OWN_POINTER);CHKERRQ(ierr);
ierr = PetscSFReduceBegin(sf,MPIU_INT,indices_ov_rd,indices_recv,MPIU_REPLACE);CHKERRQ(ierr);
ierr = PetscSFReduceEnd(sf,MPIU_INT,indices_ov_rd,indices_recv,MPIU_REPLACE);CHKERRQ(ierr);
ierr = PetscSFDestroy(&sf);CHKERRQ(ierr);
/* free memory */
ierr = PetscFree2(indices_ov_rd,sources_sc_rd);CHKERRQ(ierr);
/*create a index set*/
ierr = ISCreateGeneral(scomm,nroots,indices_recv,PETSC_OWN_POINTER,&is_sc);CHKERRQ(ierr);
/*construct a parallel submatrix */
ierr = MatGetSubMatricesMPI(mat,1,&is_sc,&is_sc,MAT_INITIAL_MATRIX,&smat);CHKERRQ(ierr);
/* we do not need them any more */
ierr = ISDestroy(&allis_sc);CHKERRQ(ierr);
/*create a partitioner to repartition the sub-matrix*/
ierr = MatPartitioningCreate(scomm,&part);CHKERRQ(ierr);
ierr = MatPartitioningSetAdjacency(part,smat[0]);CHKERRQ(ierr);
#if PETSC_HAVE_PARMETIS
/* if there exists a ParMETIS installation, we try to use ParMETIS
* because a repartition routine possibly work better
* */
ierr = MatPartitioningSetType(part,MATPARTITIONINGPARMETIS);CHKERRQ(ierr);
/*try to use reparition function, instead of partition function */
ierr = MatPartitioningParmetisSetRepartition(part);CHKERRQ(ierr);
#else
/*we at least provide a default partitioner to rebalance the computation */
ierr = MatPartitioningSetType(part,MATPARTITIONINGAVERAGE);CHKERRQ(ierr);
#endif
/*user can pick up any partitioner by using an option*/
ierr = MatPartitioningSetFromOptions(part);CHKERRQ(ierr);
/* apply partition */
ierr = MatPartitioningApply(part,&partitioning);CHKERRQ(ierr);
ierr = MatPartitioningDestroy(&part);CHKERRQ(ierr);
ierr = MatDestroy(&(smat[0]));CHKERRQ(ierr);
ierr = PetscFree(smat);CHKERRQ(ierr);
/* get local rows including overlap */
ierr = ISBuildTwoSided(partitioning,is_sc,is);CHKERRQ(ierr);
/* destroy */
ierr = ISDestroy(&is_sc);CHKERRQ(ierr);
ierr = ISDestroy(&partitioning);CHKERRQ(ierr);
ierr = PetscCommDestroy(&scomm);CHKERRQ(ierr);
PetscFunctionReturn(0);
}
