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//! Decision heuristics.
use partial_ref::{partial, PartialRef};
use varisat_formula::Var;
use crate::{
context::{parts::*, Context},
prop::{enqueue_assignment, Reason},
};
pub mod vsids;
/// Make a decision and enqueue it.
///
/// Returns `false` if no decision was made because all variables are assigned.
pub fn make_decision(
mut ctx: partial!(
Context,
mut AssignmentP,
mut ImplGraphP,
mut TrailP,
mut VsidsP
),
) -> bool {
let (vsids, mut ctx) = ctx.split_part_mut(VsidsP);
if let Some(decision_var) = vsids.find(|&var| ctx.part(AssignmentP).var_value(var).is_none()) {
let decision = decision_var.lit(ctx.part(AssignmentP).last_var_value(decision_var));
ctx.part_mut(TrailP).new_decision_level();
enqueue_assignment(ctx.borrow(), decision, Reason::Unit);
true
} else {
false
}
}
/// Make a variable available for decisions.
pub fn make_available(mut ctx: partial!(Context, mut VsidsP), var: Var) {
ctx.part_mut(VsidsP).make_available(var);
}
/// Initialize decision heuristics for a new variable.
pub fn initialize_var(mut ctx: partial!(Context, mut VsidsP), var: Var, available: bool) {
ctx.part_mut(VsidsP).reset(var);
if available {
make_available(ctx.borrow(), var);
}
}
/// Remove a variable from the decision heuristics.
pub fn remove_var(mut ctx: partial!(Context, mut VsidsP), var: Var) {
ctx.part_mut(VsidsP).make_unavailable(var);
}
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