amg4psblas/mlprec/mld_dumf_bld.f90

!!$ 
!!$ 
!!$                           MLD2P4  version 1.0
!!$  MultiLevel Domain Decomposition Parallel Preconditioners Package
!!$             based on PSBLAS (Parallel Sparse BLAS version 2.2)
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!!$
!!$                      Salvatore Filippone  University of Rome Tor Vergata       
!!$                      Alfredo Buttari      University of Rome Tor Vergata
!!$                      Pasqua D'Ambra       ICAR-CNR, Naples
!!$                      Daniela di Serafino  Second University of Naples
!!$ 
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! File: mld_dumf_bld.f90
!
! Subroutine: mld_dumf_bld
! Version:    real
!
!  This routine computes the LU factorization of the local part of the matrix
!  stored into a, by using UMFPACK. 
!  
!  The matrix to be factorized is
!  - either a submatrix of the distributed matrix corresponding to any level
!    of a multilevel preconditioner, and its factorization is used to build
!    the 'base preconditioner' corresponding to that level,
!  - or a copy of the whole matrix corresponding to the coarsest level of
!    a multilevel preconditioner, and its factorization is used to build
!    the 'base preconditioner' corresponding to the coarsest level.
!
!  The data structures allocated by UMFPACK to compute the symbolic and the
!  numeric factorization are pointed by p%iprcparm(mld_umf_symptr_) and
!  p%iprcparm(mld_umf_numptr_).
!
!
! Arguments:
!    a       -  type(psb_dspmat_type), input/output.
!               The sparse matrix structure containing the local submatrix
!               to be factorized. Note that a is intent(inout), and not only
!               intent(in), since the row and column indices of the      matrix
!               stored in a are shifted by -1, and then again by +1, by the
!               routine mld_dumf_fact, which is an interface to the UMFPACK
!               C code performing the factorization.
!    desc_a  -  type(psb_desc_type), input.
!               The communication descriptor associated to a.
!    p       -  type(mld_dbaseprec_type), input/output.
!               The 'base preconditioner' data structure containing the pointers,
!               p%iprcparm(mld_umf_symptr_) and p%iprcparm(mld_umf_numptr_),
!               to the data structures used by UMFPACK for computing the LU
!               factorization.
!    info    -  integer, output.                                                
!               Error code.
!
subroutine mld_dumf_bld(a,desc_a,p,info)

  use psb_base_mod
  use mld_inner_mod, mld_protect_name => mld_dumf_bld

  implicit none 

! Arguments
  type(psb_dspmat_type), intent(inout)      :: a
  type(psb_desc_type), intent(in)        :: desc_a
  type(mld_dbaseprec_type), intent(inout) :: p
  integer, intent(out)                   :: info

  ! Local variables
  integer           :: nzt,ictxt,me,np,err_act
  integer            :: i_err(5)
  character(len=20)  :: name

  info=0
  name='mld_dumf_bld'
  call psb_erractionsave(err_act)
  ictxt = psb_cd_get_context(desc_a)
  call psb_info(ictxt, me, np)

  if (psb_toupper(a%fida) /= 'CSC') then
    info=135
    call psb_errpush(info,name,a_err=a%fida)
    goto 9999
  endif

  nzt = psb_sp_get_nnzeros(a)

  !
  ! Compute the LU factorization
  !
  call mld_dumf_fact(a%m,nzt,&
       & a%aspk,a%ia1,a%ia2,&
       & p%iprcparm(mld_umf_symptr_),p%iprcparm(mld_umf_numptr_),info)

  if (info /= 0) then
    i_err(1) = info 
    info=4110
    call psb_errpush(info,name,a_err='mld_umf_fact',i_err=i_err)
    goto 9999
  end if

  call psb_erractionrestore(err_act)
  return

9999 continue
  call psb_erractionrestore(err_act)
  if (err_act.eq.psb_act_abort_) then
    call psb_error()
    return
  end if
  return

end subroutine mld_dumf_bld