!
! Copyright (C) 2002-2005 FPMD-CPV groups
! This file is distributed under the terms of the
! GNU General Public License. See the file `License'
! in the root directory of the present distribution,
! or http://www.gnu.org/copyleft/gpl.txt .
!

MODULE cg_module

 USE kinds, ONLY: DP

  IMPLICIT NONE
  SAVE

      logical      :: tcg        = .false.   ! if true do conjugate gradient minimization for electrons
      integer      :: maxiter    = 100      ! maximum number of iterations
      real(DP) :: conv_thr    = 1.d-5   !energy treshold 
      real(DP) :: passop    =0.3d0    !small step for conjugate gradient

!***
!***  Conjugate Gradient
!***
      real(DP)  esse,essenew !factors in c.g.
      COMPLEX(DP), ALLOCATABLE :: c0old(:,:)!old wfcs for extrapolation
      real(DP)  ene0,ene1,dene0,enever,enesti !energy terms for linear minimization along hi
      real(DP)  passof,passov !step to minimum: effective, estimated
      integer itercg !iteration number
      logical ltresh!flag for convergence on energy
      real(DP) passo!step to minimum
      real(DP) etotnew,etotold!energies
      real(DP) spasso!sign of small step
      logical tcutoff!
      logical restartcg!if .true. restart again the CG algorithm, performing a SD step
      integer numok!counter on converged iterations
      real(DP) pcnum,pcden
      integer iter3
      real(DP) ebanda
      logical ene_ok!if .true. do not recalculate energy
      integer ninner_ef


CONTAINS


  SUBROUTINE cg_init( tcg_ , maxiter_ , conv_thr_ , passop_ )
    USE kinds, ONLY: DP
    LOGICAL, INTENT(IN) :: tcg_
    INTEGER, INTENT(IN) :: maxiter_
    REAL(DP), INTENT(IN) :: conv_thr_ , passop_
    tcg=tcg_
    maxiter=maxiter_
    conv_thr=conv_thr_
    passop=passop_
    IF (tcg) CALL cg_info()
    RETURN
  END SUBROUTINE cg_init

  SUBROUTINE cg_info()
    USE io_global, ONLY: stdout 
    if(tcg) then
       write (stdout,400) maxiter,conv_thr,passop                         
    endif
400 format (/4x,'========================================'                          &
   &        /4x,'|  CONJUGATE GRADIENT                  |'                          &
   &        /4x,'========================================'                          &
   &        /4x,'| iterations   =',i14,'         |'                             &
   &        /4x,'| conv_thr     =',f14.11,' a.u.    |'                           &
   &        /4x,'| passop       =',f14.5,' a.u.    |'                           &
   &        /4x,'========================================')
    RETURN
  END SUBROUTINE cg_info


  SUBROUTINE allocate_cg( ngw, nx, nhsavb )
    IMPLICIT NONE
    INTEGER, INTENT(IN) :: ngw, nx, nhsavb
    allocate(c0old(ngw,nx))
    RETURN
  END SUBROUTINE allocate_cg

  SUBROUTINE deallocate_cg( )
    IMPLICIT NONE
    IF( ALLOCATED( c0old ) ) deallocate(c0old )
    RETURN
  END SUBROUTINE deallocate_cg

  SUBROUTINE cg_update( tfirst, nfi, c0 )
    use gvecw, only: ngw
    use electrons_base, only: n => nbsp
    IMPLICIT NONE
    COMPLEX(DP) :: c0( :, :, :, : )
    INTEGER :: nfi
    LOGICAL :: tfirst
    INTEGER :: i, ig
    if(.not. tfirst.and.(mod(nfi,10).ne.1)) then
      call DSWAP(2*ngw*n,c0,1,c0old,1)
      do i=1,n
        do ig=1,ngw
          c0(ig,i,1,1)=-c0(ig,i,1,1)+2.d0*c0old(ig,i)
        enddo
      enddo
    else
      do i=1,n
        do ig=1,ngw
          c0old(ig,i)=c0(ig,i,1,1)
        enddo
      enddo
    endif
    RETURN
  END SUBROUTINE cg_update

  SUBROUTINE print_clock_tcg()
  CALL print_clock( 'runcg_uspp')
  CALL print_clock( 'inner_loop')
  CALL print_clock( 'rotate' )
  CALL print_clock( 'calcmt' )
  CALL print_clock( 'calcm' )
  CALL print_clock( 'pc2' )
  CALL print_clock( 'pcdaga2' )
  CALL print_clock( 'set_x_minus1' )
  CALL print_clock( 'xminus1' )
  CALL print_clock( 'emass_p_tpa' )
  CALL print_clock( 'mxma' )
  return
  END SUBROUTINE print_clock_tcg

END MODULE cg_module