en_pert_t Derived Type

    type en_pert_t
        ! The number of integers available to store signs, for each
        ! RDM entry in the elements array.
        integer :: sign_length = 0
        ! Array which holds the RDM elements.
        integer(n_int), allocatable :: dets(:, :)
        ! Hash table to the rdm array.
        type(ll_node), pointer :: hash_table(:)
        ! The allocated size of the elements array.
        integer :: max_ndets = 0
        ! The number of determinants contributing to the perturbation
        ! currently stored in the dets array.
        integer :: ndets = 0
        ! The number of determinants contributing to the perturbation
        ! currently stored in the dets array, across all processors.
        integer :: ndets_all = 0
        ! Maximum number of unique hashes available in hash_table (not the
        ! number of currently unused ones, but the total number, i.e. the
        ! length of the hash_table array).
        integer :: nhashes = 0
    end type en_pert_t