amg4psblas/mlprec/impl/mld_daggrmat_nosmth_asb.f90

!!$ 
!!$ 
!!$                           MLD2P4  version 2.1
!!$  MultiLevel Domain Decomposition Parallel Preconditioners Package
!!$             based on PSBLAS (Parallel Sparse BLAS version 3.4)
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!!$      Salvatore Filippone    Cranfield University
!!$      Ambra Abdullahi Hassan University of Rome Tor Vergata
!!$      Alfredo Buttari        CNRS-IRIT, Toulouse
!!$      Pasqua D'Ambra         ICAR-CNR, Naples
!!$      Daniela di Serafino    University of Campania "L. Vanvitelli", Caserta
!!$ 
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! File: mld_daggrmat_nosmth_asb.F90
!
! Subroutine: mld_daggrmat_nosmth_asb
! Version:    real
!
!  This routine builds a coarse-level matrix A_C from a fine-level matrix A
!  by using the Galerkin approach, i.e.
!
!                               A_C = P_C^T A P_C,
!
!  where P_C is the piecewise constant interpolation operator corresponding
!  the fine-to-coarse level mapping built by mld_aggrmap_bld.
! 
!  The coarse-level matrix A_C is distributed among the parallel processes or
!  replicated on each of them, according to the value of p%parms%coarse_mat
!  specified by the user through mld_dprecinit and mld_zprecset.
!  On output from this routine the entries of AC, op_prol, op_restr
!  are still in "global numbering" mode; this is fixed in the calling routine
!  mld_d_lev_aggrmat_asb.
!
!  For details see
!    P. D'Ambra, D. di Serafino and  S. Filippone, On the development of
!    PSBLAS-based parallel two-level Schwarz preconditioners, Appl. Num. Math.,
!    57 (2007), 1181-1196.
!
!
! Arguments:
!    a          -  type(psb_dspmat_type), input.     
!                  The sparse matrix structure containing the local part of
!                  the fine-level matrix.
!    desc_a     -  type(psb_desc_type), input.
!                  The communication descriptor of the fine-level matrix.
!    p          -  type(mld_d_onelev_type), input/output.
!                  The 'one-level' data structure that will contain the local
!                  part of the matrix to be built as well as the information
!                  concerning the prolongator and its transpose.
!    parms      -   type(mld_dml_parms), input
!                  Parameters controlling the choice of algorithm
!    ac         -  type(psb_dspmat_type), output
!                  The coarse matrix on output 
!                  
!    ilaggr     -  integer, dimension(:), input
!                  The mapping between the row indices of the coarse-level
!                  matrix and the row indices of the fine-level matrix.
!                  ilaggr(i)=j means that node i in the adjacency graph
!                  of the fine-level matrix is mapped onto node j in the
!                  adjacency graph of the coarse-level matrix. Note that the indices
!                  are assumed to be shifted so as to make sure the ranges on
!                  the various processes do not   overlap.
!    nlaggr     -  integer, dimension(:) input
!                  nlaggr(i) contains the aggregates held by process i.
!    op_prol    -  type(psb_dspmat_type), input/output
!                  The tentative prolongator on input, the computed prolongator on output
!               
!    op_restr    -  type(psb_dspmat_type), output
!                  The restrictor operator; normally, it is the transpose of the prolongator. 
!               
!    info       -  integer, output.
!                  Error code.
!
!
subroutine mld_daggrmat_nosmth_asb(a,desc_a,ilaggr,nlaggr,parms,ac,op_prol,op_restr,info)
  use psb_base_mod
  use mld_d_inner_mod, mld_protect_name => mld_daggrmat_nosmth_asb

  implicit none

  ! Arguments
  type(psb_dspmat_type), intent(in)        :: a
  type(psb_desc_type), intent(in)            :: desc_a
  integer(psb_ipk_), intent(inout)           :: ilaggr(:), nlaggr(:)
  type(mld_dml_parms), intent(inout)      :: parms 
  type(psb_dspmat_type), intent(inout)     :: op_prol
  type(psb_dspmat_type), intent(out)       :: ac,op_restr
  integer(psb_ipk_), intent(out)             :: info

  ! Local variables
  integer(psb_ipk_)  :: err_act
  integer(psb_ipk_)  :: ictxt,np,me, icomm, ndx, minfo
  character(len=20)  :: name
  integer(psb_ipk_)  :: ierr(5) 
  type(psb_d_coo_sparse_mat) :: ac_coo, acoo
  type(psb_d_csr_sparse_mat) :: acsr1, acsr2
  integer(psb_ipk_) :: debug_level, debug_unit
  integer(psb_ipk_) :: nrow, nglob, ncol, ntaggr, nzl, ip, &
       & naggr, nzt, naggrm1, i, k

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


  ictxt = desc_a%get_context()
  icomm = desc_a%get_mpic()
  call psb_info(ictxt, me, np)
  nglob = desc_a%get_global_rows()
  nrow  = desc_a%get_local_rows()
  ncol  = desc_a%get_local_cols()


  naggr  = nlaggr(me+1)
  ntaggr = sum(nlaggr)
  naggrm1=sum(nlaggr(1:me))

  call acoo%allocate(ncol,ntaggr,ncol)

  call op_prol%cscnv(info,type='csr',dupl=psb_dupl_add_)
  if (info /= psb_success_) goto 9999
  call op_prol%transp(op_restr)
  
  call a%cp_to(ac_coo)

  nzt = ac_coo%get_nzeros()
  k = 0
  do i=1, nzt 
    k = k + 1 
    ac_coo%ia(k)  = ilaggr(ac_coo%ia(i))
    ac_coo%ja(k)  = ilaggr(ac_coo%ja(i))
    ac_coo%val(k) = ac_coo%val(i)
  enddo
  call ac_coo%set_nrows(naggr)
  call ac_coo%set_ncols(naggr)
  call ac_coo%set_nzeros(k)
  call ac_coo%set_dupl(psb_dupl_add_)
  call ac_coo%fix(info)
  call ac%mv_from(ac_coo) 


  call psb_erractionrestore(err_act)
  return

9999 call psb_error_handler(err_act)

  return

end subroutine mld_daggrmat_nosmth_asb