quantum-espresso/VdW/pbcg_psi.f90

48 lines
1.4 KiB
Fortran

!
! Copyright (C) 2001 PWSCF group
! 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 .
!
!
!-----------------------------------------------------------------
subroutine pbcg_psi (lda, n, m, psi, h_diag, flag)
!-----------------------------------------------------------------
!
! This routine gives a preconditioning to the linear system solver.
! The preconditioning is diagonal in reciprocal space
!
!
USE kinds, only : DP
implicit none
integer :: lda, n, m, flag
! input: the leading dimension of the psi vector
! input: the real dimension of the vector
! input: the number of vectors
! input: flag=1 use h_diag, flag=-1 use CONJG(h_diag)
complex(kind=DP) :: psi (lda, m)
! inp/out: the vector to be preconditioned
complex(kind=DP) :: h_diag (lda, m)
! input: the preconditioning vector
integer :: k, i
! counter on bands
! counter on the elements of the vector
!
do k = 1, m
do i = 1, n
if (flag .eq. 1) then
psi (i, k) = psi (i, k) * h_diag (i, k)
else if (flag .eq. -1) then
psi (i, k) = psi (i, k) * CONJG(h_diag (i, k))
else
print*, 'flag is neither 1 nor -1. Stop'
endif
enddo
enddo
return
end subroutine pbcg_psi