C++ (Cpp) PCBDDCSetLocalAdjacencyGraph Examples

Example #1

PETSC_EXTERN void PETSC_STDCALL  pcbddcsetlocaladjacencygraph_(PC pc,PetscInt *nvtxs, PetscInt xadj[], PetscInt adjncy[],PetscCopyMode *copymode, int *__ierr ){
*__ierr = PCBDDCSetLocalAdjacencyGraph(
	(PC)PetscToPointer((pc) ),*nvtxs,xadj,adjncy,*copymode);
}

Example #2

File: ex59.c Project: tom-klotz/petsc

static PetscErrorCode ComputeKSPBDDC(DomainData dd,Mat A,KSP *ksp)
{
  PetscErrorCode ierr;
  KSP            temp_ksp;
  PC             pc;
  IS             dirichletIS=0,neumannIS=0,*bddc_dofs_splitting;
  PetscInt       localsize,*xadj=NULL,*adjncy=NULL;
  MatNullSpace   near_null_space;

  PetscFunctionBeginUser;
  ierr = KSPCreate(dd.gcomm,&temp_ksp);CHKERRQ(ierr);
  ierr = KSPSetOperators(temp_ksp,A,A);CHKERRQ(ierr);
  ierr = KSPSetType(temp_ksp,KSPCG);CHKERRQ(ierr);
  ierr = KSPGetPC(temp_ksp,&pc);CHKERRQ(ierr);
  ierr = PCSetType(pc,PCBDDC);CHKERRQ(ierr);

  localsize = dd.xm_l*dd.ym_l*dd.zm_l;

  /* BDDC customization */

  /* jumping coefficients case */
  ierr = PCISSetSubdomainScalingFactor(pc,dd.scalingfactor);CHKERRQ(ierr);

  /* Dofs splitting
     Simple stride-1 IS
     It is not needed since, by default, PCBDDC assumes a stride-1 split */
  ierr = PetscMalloc1(1,&bddc_dofs_splitting);CHKERRQ(ierr);
#if 1
  ierr = ISCreateStride(PETSC_COMM_WORLD,localsize,0,1,&bddc_dofs_splitting[0]);CHKERRQ(ierr);
  ierr = PCBDDCSetDofsSplittingLocal(pc,1,bddc_dofs_splitting);CHKERRQ(ierr);
#else
  /* examples for global ordering */

  /* each process lists the nodes it owns */
  PetscInt sr,er;
  ierr = MatGetOwnershipRange(A,&sr,&er);CHKERRQ(ierr);
  ierr = ISCreateStride(PETSC_COMM_WORLD,er-sr,sr,1,&bddc_dofs_splitting[0]);CHKERRQ(ierr);
  ierr = PCBDDCSetDofsSplitting(pc,1,bddc_dofs_splitting);CHKERRQ(ierr);
  /* Split can be passed in a more general way since any process can list any node */
#endif
  ierr = ISDestroy(&bddc_dofs_splitting[0]);CHKERRQ(ierr);
  ierr = PetscFree(bddc_dofs_splitting);CHKERRQ(ierr);

  /* Primal constraints implemented by using a near null space attached to A -> now it passes in only the constants
    (which in practice is not needed since, by default, PCBDDC build the primal space using constants for quadrature formulas */
#if 0
  Vec vecs[2];
  PetscRandom rctx;
  ierr = MatCreateVecs(A,&vecs[0],&vecs[1]);CHKERRQ(ierr);
  ierr = PetscRandomCreate(dd.gcomm,&rctx);CHKERRQ(ierr);
  ierr = VecSetRandom(vecs[0],rctx);CHKERRQ(ierr);
  ierr = VecSetRandom(vecs[1],rctx);CHKERRQ(ierr);
  ierr = MatNullSpaceCreate(dd.gcomm,PETSC_TRUE,2,vecs,&near_null_space);CHKERRQ(ierr);
  ierr = VecDestroy(&vecs[0]);CHKERRQ(ierr);
  ierr = VecDestroy(&vecs[1]);CHKERRQ(ierr);
  ierr = PetscRandomDestroy(&rctx);CHKERRQ(ierr);
#else
  ierr = MatNullSpaceCreate(dd.gcomm,PETSC_TRUE,0,NULL,&near_null_space);CHKERRQ(ierr);
#endif
  ierr = MatSetNearNullSpace(A,near_null_space);CHKERRQ(ierr);
  ierr = MatNullSpaceDestroy(&near_null_space);CHKERRQ(ierr);

  /* CSR graph of subdomain dofs */
  ierr = BuildCSRGraph(dd,&xadj,&adjncy);CHKERRQ(ierr);
  ierr = PCBDDCSetLocalAdjacencyGraph(pc,localsize,xadj,adjncy,PETSC_OWN_POINTER);CHKERRQ(ierr);

  /* Neumann/Dirichlet indices on the global boundary */
  if (dd.DBC_zerorows) {
    /* Only in case you eliminate some rows matrix with zerorows function, you need to set dirichlet indices into PCBDDC data */
    ierr = ComputeSpecialBoundaryIndices(dd,&dirichletIS,&neumannIS);CHKERRQ(ierr);
    ierr = PCBDDCSetNeumannBoundariesLocal(pc,neumannIS);CHKERRQ(ierr);
    ierr = PCBDDCSetDirichletBoundariesLocal(pc,dirichletIS);CHKERRQ(ierr);
  } else {
    if (dd.pure_neumann) {
      /* In such a case, all interface nodes lying on the global boundary are neumann nodes */
      ierr = ComputeSpecialBoundaryIndices(dd,NULL,&neumannIS);CHKERRQ(ierr);
      ierr = PCBDDCSetNeumannBoundariesLocal(pc,neumannIS);CHKERRQ(ierr);
    } else {
      /* It is wrong setting dirichlet indices without having zeroed the corresponding rows in the global matrix */
      /* But we can still compute them since nodes near the dirichlet boundaries does not need to be defined as neumann nodes */
      ierr = ComputeSpecialBoundaryIndices(dd,&dirichletIS,&neumannIS);CHKERRQ(ierr);
      ierr = PCBDDCSetNeumannBoundariesLocal(pc,neumannIS);CHKERRQ(ierr);
    }
  }

  /* Pass local null space information to local matrices (needed when using approximate local solvers) */
  if (dd.ipx || dd.pure_neumann) {
    MatNullSpace nsp;
    Mat          local_mat;

    ierr = MatISGetLocalMat(A,&local_mat);CHKERRQ(ierr);
    ierr = MatNullSpaceCreate(PETSC_COMM_SELF,PETSC_TRUE,0,NULL,&nsp);CHKERRQ(ierr);
    ierr = MatSetNullSpace(local_mat,nsp);CHKERRQ(ierr);
    ierr = MatNullSpaceDestroy(&nsp);CHKERRQ(ierr);
  }
  ierr = KSPSetComputeSingularValues(temp_ksp,PETSC_TRUE);CHKERRQ(ierr);
  ierr = KSPSetFromOptions(temp_ksp);CHKERRQ(ierr);
  ierr = KSPSetUp(temp_ksp);CHKERRQ(ierr);
  *ksp = temp_ksp;
  ierr = ISDestroy(&dirichletIS);CHKERRQ(ierr);
  ierr = ISDestroy(&neumannIS);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}