init_en_pert_t Subroutine

    subroutine init_en_pert_t(en_pert, sign_length, max_ndets, nhashes)

        ! Initialise an en_pert_t object.

        ! Out: en_pert - en_pert_t object to be initialised.
        ! In:  sign_length - the number of signs which can be stored for each element.
        ! In:  max_ndets - the length of the en_pert%dets array.
        ! In:  nhashes - the number of unique hashes for indexing the hash table.

        use hash, only: init_hash_table

        type(en_pert_t), intent(out) :: en_pert
        integer, intent(in) :: sign_length, max_ndets, nhashes

        integer :: ierr

        en_pert%sign_length = sign_length
        en_pert%max_ndets = max_ndets
        en_pert%nhashes = nhashes
        en_pert%ndets = 0

        allocate(en_pert%dets(0:sign_length + nifd, max_ndets))
        en_pert%dets = 0_n_int

        allocate(en_pert%hash_table(nhashes), stat=ierr)
        call init_hash_table(en_pert%hash_table)

    end subroutine init_en_pert_t