fn concretize_cube(cube: &mut [OptBool]) {

    for bit in cube {

        if *bit == OptBool::None {

            *bit = OptBool::False;

        }

}

pub fn convert_symbolic_lts_bdd<B: LtsBuilder<String>>(

    _manager_ref: &BDDManagerRef,

    output: &mut B,

    lts: &SymbolicLtsBdd,

) -> Result<B::LTS, MercError> {

    let state_variables = lts.state_variables().to_vec();

    let next_state_variables = lts.next_state_variables().to_vec();

    let action_variables = lts.action_variables().to_vec();

    let state_variable_indices = state_variables

        .iter()

        .enumerate()

        .map(|(index, &var)| (var, index))

        .collect::<FxHashMap<VarNo, usize>>();

    let next_state_variable_indices = next_state_variables

        .iter()

        .enumerate()

        .map(|(index, &var)| (var, index))

        .collect::<FxHashMap<VarNo, usize>>();

    let state_group_offsets = {

        let mut offsets = Vec::with_capacity(lts.state_variable_num_of_bits().len());

        let mut offset = 0usize;

        for &num_of_bits in lts.state_variable_num_of_bits() {

            offsets.push(offset);

            offset += num_of_bits as usize;

        }

        offsets

    let read_groups = lts

        .transition_groups()

        .iter()

        .map(|group| {

            group

                .read_variables()

                .iter()

                .map(|var| {

                    *state_variable_indices

                        .get(var)

                        .expect("Read variable was not found in state variables")

                })

                .collect::<FxHashSet<usize>>()

        })

        .collect::<Vec<_>>();

    let write_groups = lts

        .transition_groups()

        .iter()

        .map(|group| {

            group

                .write_variables()

                .iter()

                .map(|var| {

                    *next_state_variable_indices

                        .get(var)

                        .expect("Write variable was not found in next-state variables")

                })

                .collect::<FxHashSet<usize>>()

        })

        .collect::<Vec<_>>();

    let mut read_positions = Vec::new();

    let mut write_positions = Vec::new();

    let mut transition_variables = Vec::new();

    let mut action_positions = Vec::new();

    for (group_index, _group) in lts.transition_groups().iter().enumerate() {

        let mut variables = Vec::new();

        let (rpos, wpos) = compute_positions(

            &state_variables,

            &next_state_variables,

            &action_variables,

            &state_group_offsets,

            &read_groups[group_index],

            &write_groups[group_index],

            &mut variables,

        );

        let action_start = variables.len() - action_variables.len();

        action_positions.push(action_start);

        transition_variables.push(variables);

        read_positions.push(rpos);

        write_positions.push(wpos);

    }

    let total_number_of_states: u64 = lts.states().sat_count(

        lts.state_variables().len() as VarNo,

        &mut SatCountCache::<u64, FxBuildHasher>::default(),

    info!(

    let state_progress = TimeProgress::new(

        move |number_of_states| {

            info!(

        },

    let mut discovered: IndexedSet<Vec<OptBool>, FxBuildHasher> = IndexedSet::new();

    for cube in CubeIterAll::with_variables(lts.states(), &state_variables) {

        let mut cube = cube?;

        concretize_cube(&mut cube);

        let (_, inserted) = discovered.insert(cube);

        debug_assert!(inserted, "State space contains duplicate states");

        state_progress.print(discovered.len())

    let progress = TimeProgress::new(

        move |(number_of_states, number_of_transitions)| {

            info!(

        },

    let mut outgoing = FxHashSet::default();

    let mut target = vec![OptBool::False; state_variables.len()];

    let mut index = 0usize;

    for cube in CubeIterAll::with_variables(lts.states(), &state_variables) {

        let mut cube = cube?;

        concretize_cube(&mut cube);

        let state_index = discovered

            .index(&cube)

            .ok_or("Found state that was not in the state set")?;

        for (group_index, group) in lts.transition_groups().iter().enumerate() {

            for transition in CubeIterAll::with_variables(group.relation(), &transition_variables[group_index]) {

                let mut transition = transition?;

                concretize_cube(&mut transition);

                let mut matches = true;

                for (&read_variable, &read_position) in

                    group.read_variables().iter().zip(read_positions[group_index].iter())

                    let state_pos = *state_variable_indices

                        .get(&read_variable)

                        .expect("Read variable was not found in state variables");

                    if cube[state_pos] != transition[read_position] {

                        matches = false;

                        break;

                    }

                if !matches {

                    continue;

                }

                target.clone_from_slice(&cube);

                trace!("transition {:?}", transition);

                for (&write_variable, &write_position) in

                    group.write_variables().iter().zip(write_positions[group_index].iter())

                {

                    let state_pos = *next_state_variable_indices

                        .get(&write_variable)

                        .expect("Write variable was not found in next-state variables");

                    target[state_pos] = transition[write_position];

                }

                let action_bits = &transition[action_positions[group_index]..];

                let action_value = to_value(action_bits);

                let label = lts

                    .action_labels()

                    .get(action_value as usize)

                    .ok_or("Found transition with unknown action label")?;

                let target_index = discovered

                    .index(&target)

                    .ok_or("Found state that was not in the state set")?;

                if outgoing.insert((*state_index, action_value, *target_index)) {

                    trace!(

                    output.add_transition(StateIndex::new(*state_index), label, StateIndex::new(*target_index))?;

                }

        progress.print((index, output.num_of_transitions()));

        index += 1;

        outgoing.clear();

    let mut initial_state = CubeIterAll::with_variables(lts.initial_state(), &state_variables);

    let mut initial_state = initial_state.next().ok_or("Symbolic LTS has no initial state")??;

    concretize_cube(&mut initial_state);

    let initial_state_index = discovered

        .index(&initial_state)

        .ok_or("Initial state was not found in the discovered state set")?;

    output.finish(StateIndex::new(*initial_state_index))

}

fn compute_positions(

    state_variables: &[VarNo],

    next_state_variables: &[VarNo],

    action_variables: &[VarNo],

    state_group_offsets: &[usize],

    read_group: &FxHashSet<usize>,

    write_group: &FxHashSet<usize>,

    transition_variables: &mut Vec<VarNo>,

) -> (Vec<usize>, Vec<usize>) {

    let mut rpos = Vec::new();

    let mut wpos = Vec::new();

    for (state_group, &offset) in state_group_offsets.iter().enumerate() {

        let end = state_group_offsets

            .get(state_group + 1)

            .copied()

            .unwrap_or(state_variables.len());

        if read_group.contains(&offset) {

            for bit in state_variables.iter().take(end).skip(offset) {

                rpos.push(transition_variables.len());

                transition_variables.push(*bit);

            }

        }

        if write_group.contains(&offset) {

            for bit in next_state_variables.iter().take(end).skip(offset) {

                wpos.push(transition_variables.len());

                transition_variables.push(*bit);

            }

        }

    transition_variables.extend(action_variables.iter().copied());

    (rpos, wpos)

}

    fn test_convert_symbolic_lts_bdd_abp() {

        test_logger();

        let input = include_bytes!("../../../examples/lts/abp.sym");

        let mut storage = Storage::new();

        let manager_ref = oxidd::bdd::new_manager(2048, 1024, 1);

        let symbolic_lts = read_symbolic_lts(&mut storage, &input[..]).unwrap();

        let symbolic_lts_bdd = SymbolicLtsBdd::from_symbolic_lts(&mut storage, &manager_ref, &symbolic_lts).unwrap();

        let mut builder = LtsBuilderMem::new(Vec::new(), Vec::new());

        let lts = convert_symbolic_lts_bdd(&manager_ref, &mut builder, &symbolic_lts_bdd).unwrap();

        assert_eq!(lts.num_of_states(), 74);

        assert_eq!(lts.num_of_transitions(), 92);

    }

    fn test_random_convert_symbolic_lts_bdd() {

        random_test(100, |rng| {

            let mut storage = Storage::new();

            let lts = random_symbolic_lts(rng, &mut storage, 10, 5).unwrap();

            let mut builder = LtsBuilderMem::new(Vec::new(), Vec::new());

            let explicit_lts = convert_symbolic_lts(&mut storage, &mut builder, &lts).unwrap();

            let manager_ref = oxidd::bdd::new_manager(2028, 2028, 1);

            let lts_bdd = SymbolicLtsBdd::from_symbolic_lts(&mut storage, &manager_ref, &lts).unwrap();

            let mut builder = LtsBuilderMem::new(Vec::new(), Vec::new());

            let explicit_lts_bdd = convert_symbolic_lts_bdd(&manager_ref, &mut builder, &lts_bdd).unwrap();

            assert!(

                compare_lts(

                    Equivalence::StrongBisim,

                    explicit_lts,

                    explicit_lts_bdd,

                    &mut Timing::new()

        });

    }