Struct ddo::Decreasing

pub struct Decreasing;

This strategy selects the variable in decreasing order. This means, it has provides and order which is the opposite of the NaturalOrder.

Example

let mut variables = VarSet::all(3);
assert_eq!(Some(Variable(2)), Decreasing.next_var(&variables, &mut current_layer, &mut next_layer));

variables.remove(Variable(2)); // move on to the next layer
assert_eq!(Some(Variable(1)), Decreasing.next_var(&variables, &mut current_layer, &mut next_layer));

variables.remove(Variable(1)); // move on to the next layer
assert_eq!(Some(Variable(0)), Decreasing.next_var(&variables, &mut current_layer, &mut next_layer));

variables.remove(Variable(0)); // move on to the last layer, no more var to branch on
assert_eq!(None, Decreasing.next_var(&variables, &mut current_layer, &mut next_layer));

Note:

Even though any variable heuristic may access the current and next layers of the mdd being developed, the natural ordering heuristic does not use that access.

Trait Implementations

impl Clone for Decreasing

pub fn clone(&self) -> Decreasing

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Decreasing

impl Debug for Decreasing

pub fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Decreasing

pub fn default() -> Decreasing

Returns the "default value" for a type.

impl<T> VariableHeuristic<T> for Decreasing

pub fn next_var(
    &self,
    vars: &VarSet,
    _: &mut dyn Iterator<Item = &T>,
    _: &mut dyn Iterator<Item = &T>
) -> Option<Variable>

Returns the best variable to branch on from the set of free_vars or None in case no branching is useful (free_vars is empty, no decision left to make, etc...).