calc_hamil_contribs_diag Subroutine

public subroutine calc_hamil_contribs_diag(nvecs, krylov_array, ndets, h_matrix, h_diag)


Type IntentOptional Attributes Name
integer, intent(in) :: nvecs
integer(kind=n_int), intent(in) :: krylov_array(0:,:)
integer, intent(in) :: ndets
real(kind=dp), intent(inout) :: h_matrix(:,:)
real(kind=dp), intent(in), optional :: h_diag(:)


Source Code

    subroutine calc_hamil_contribs_diag(nvecs, krylov_array, ndets, h_matrix, h_diag)

        use bit_rep_data, only: IlutBits
        use FciMCData, only: Hii
        use core_space_util, only: cs_replicas
        use global_det_data, only: det_diagH
        use kp_fciqmc_data_mod, only: tSemiStochasticKPHamil
        use Parallel_neci, only: iProcIndex
        use SystemData, only: nel

        integer, intent(in) :: nvecs
        integer(n_int), intent(in) :: krylov_array(0:, :)
        integer, intent(in) :: ndets
        real(dp), intent(inout) :: h_matrix(:, :)
        real(dp), intent(in), optional :: h_diag(:)

        integer :: idet, i, j, min_idet
        integer :: nI_spawn(nel)
        integer(n_int) :: int_sign(lenof_all_signs)
        real(dp) :: real_sign(lenof_all_signs)
        real(dp) :: h_diag_elem

        ! In semi-stochastic calculations the diagonal elements of the core space
        ! are taken care of in the core Hamiltonian calculation, so skip them here.
        ! Core determinants are always kept at the top of the list, so they're simple
        ! to skip.
        if (tSemiStochasticKPHamil) then
            min_idet = cs_replicas(1)%determ_sizes(iProcIndex) + 1
            min_idet = 1
        end if

        do idet = min_idet, ndets
            int_sign = krylov_array(IlutBits%ind_pop:IlutBits%ind_pop + lenof_all_signs - 1, idet)
            real_sign = transfer(int_sign, real_sign)
            if (present(h_diag)) then
                h_diag_elem = h_diag(idet) + Hii
                h_diag_elem = det_diagH(idet) + Hii
            end if

            ! Finally, add in the contribution to the projected Hamiltonian for each pair of Krylov vectors.
            do i = 1, nvecs
                do j = i, nvecs
                    h_matrix(i, j) = h_matrix(i, j) + &
                                     h_diag_elem * (real_sign(kp_ind_1(i)) * real_sign(kp_ind_2(j)) + &
                                                    real_sign(kp_ind_2(i)) * real_sign(kp_ind_1(j))) / 2.0_dp
                end do
            end do

        end do

    end subroutine calc_hamil_contribs_diag