amg4psblas/mlprec/mld_zslud_bld.f90

!!$ 
!!$ 
!!$                           MLD2P4  version 2.0
!!$  MultiLevel Domain Decomposition Parallel Preconditioners Package
!!$             based on PSBLAS (Parallel Sparse BLAS version 3.0)
!!$  
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!!$
!!$                      Salvatore Filippone  University of Rome Tor Vergata
!!$                      Alfredo Buttari      CNRS-IRIT, Toulouse
!!$                      Pasqua D'Ambra       ICAR-CNR, Naples
!!$                      Daniela di Serafino  Second University of Naples
!!$ 
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! File: mld_zslud_bld.f90
!
! Subroutine: mld_zsludist_bld
! Version:    real
!
!  This routine computes the LU factorization of of a distributed matrix,
!  by using SuperLU_DIST. 
!  
!  The matrix to be factorized is the coarsest-level matrix of a multilevel
!  preconditioner and is distributed among the processes. Its factorization
!  is used to build the 'base preconditioner' corresponding to the coarsest
!  level.
!
!  The data structure allocated by SuperLU_DIST to store the L and U factors
!  is pointed by p%iprcparm(mld_slud_ptr_).
!
!
! Arguments:
!    a       -  type(psb_zspmat_type), input/output.
!               The sparse matrix structure containing the local part of the
!               matrix to be factorized.
!    desc_a  -  type(psb_desc_type), input.
!               The communication descriptor associated to a.
!    p       -  type(mld_zbaseprec_type), input/output.
!               The 'base preconditioner' data structure containing the pointer, 
!               p%iprcparm(mld_slud_ptr_), to the data structure used by 
!               SuperLU_DIST to store the L and U factors.
!    info    -  integer, output.                                                             
!               Error code.
!  
subroutine mld_zsludist_bld(a,desc_a,p,info)

  use psb_sparse_mod
  use mld_inner_mod, mld_protect_name => mld_zsludist_bld

  implicit none 

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

  ! Local variables
  integer            :: nzt,ictxt,me,np,err_act,&
       &                mglob,ifrst,ibcheck,nrow,ncol,npr,npc
  character(len=20)  :: name, ch_err

  if(psb_get_errstatus().ne.0) return 
  info=psb_success_
  name='mld_zslud_bld'
  call psb_erractionsave(err_act)

  ictxt = psb_cd_get_context(desc_a)

  call psb_info(ictxt, me, np)

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

  !
  ! WARN: we need to check for a BLOCK distribution (this is the
  ! distribution required by SuperLU_DIST)  
  !
  nrow = psb_cd_get_local_rows(desc_a)
  ncol = psb_cd_get_local_cols(desc_a)
  call psb_loc_to_glob(1,ifrst,desc_a,info) 
  call psb_loc_to_glob(nrow,ibcheck,desc_a,info) 
  ibcheck = ibcheck - ifrst + 1 
  ibcheck = ibcheck - nrow
  call psb_amx(ictxt,ibcheck)
  if (ibcheck > 0) then 
    write(0,*) 'Warning: does not look like a BLOCK distribution'
  endif

  mglob = psb_cd_get_global_rows(desc_a)
  nzt   = psb_sp_get_nnzeros(a)

  npr = np
  npc = 1
  call psb_loc_to_glob(a%ia1(1:nzt),desc_a,info,iact='I')
  
  !
  ! Compute the LU factorization
  !
  call mld_zsludist_fact(mglob,nrow,nzt,ifrst,&
       & a%aspk,a%ia2,a%ia1,p%iprcparm(mld_slud_ptr_),&
       & npr, npc, info)
  if (info /= psb_success_) then
    ch_err='psb_sludist_fact'
    call psb_errpush(4110,name,a_err=ch_err,i_err=(/info,0,0,0,0/))
    goto 9999
  end if
  
  call psb_glob_to_loc(a%ia1(1:nzt),desc_a,info,iact='I')

  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_zsludist_bld