get_pgen_pick_weighted_hole Function

    function get_pgen_pick_weighted_hole(this, nI, exc) result(pgenVal)
        class(GAS_disc_ExcGenerator_t), intent(in) :: this
        integer, intent(in) :: nI(nel)
        type(Excite_2_t), intent(in) :: exc
        character(*), parameter :: this_routine = 'get_pgen_pick_weighted_hole'

        real(dp) :: pgenVal

        integer :: src1, tgt1, src2, tgt2
        real(dp) :: cSum(this%GAS_size(this%GAS_table(exc%val(2, 2))))
        integer :: gasList(this%GAS_size(this%GAS_table(exc%val(2, 2)))), nOrbs
        integer :: gasInd2

#ifdef DEBUG_
    block
        use util_mod, only: stop_all
        use constants, only: stderr
        if (.not. (defined(exc))) then
            write(stderr, *) ""
            write(stderr, *) "Assertion defined(exc)"
            write(stderr, *) "failed in /scratch/jenkins/jobs/existing_branch_doc/workspace/build_config/gfortran-doc/src/gasci_dis&
                &connected.fpp:388"
            call stop_all (this_routine, "Assert fail: defined(exc)")
        end if
    end block
#endif
        src1 = exc%val(1, 1); tgt1 = exc%val(2, 1)
        src2 = exc%val(1, 2); tgt2 = exc%val(2, 2)

        nOrbs = this%GAS_size(this%GAS_table(tgt2))
        gasList = this%GAS_spin_orb_list(1:nOrbs, this%GAS_table(tgt2), get_spin(tgt2))

        cSum = get_cumulative_list(gasList, nI, Excite_2_t(src1, tgt1, src2))
        ! we know gasList contains tgt2, so we can look up its index with binary search
        gasInd2 = binary_search_first_ge(gasList, tgt2)
        if (gasInd2 == 1) then
            pgenVal = cSum(1)
        else
            pgenVal = (cSum(gasInd2) - cSum(gasInd2 - 1))
        end if
    end function get_pgen_pick_weighted_hole