csp_solver/constraint/
dispatch.rs

1//! ConstraintEnum: devirtualized dispatch for hot-path constraints.
2
3use crate::domain::Domain;
4use crate::variable::Variable;
5
6use super::all_different::AllDifferent;
7use super::all_different_except::AllDifferentExcept;
8use super::not_equal::NotEqual;
9use super::soft::SoftLambdaConstraint;
10use super::traits::{Constraint, Revision, VarId};
11
12/// Enum-dispatched constraint storage. Avoids vtable indirection for built-in types.
13///
14/// There is deliberately no `Lambda` variant: every closure-based constraint
15/// (`add_equals`, `add_less_than`, `add_greater_than`, and external
16/// `LambdaConstraint`s) enters through [`Custom`](Self::Custom), which boxes
17/// the `dyn Constraint`. A devirtualized `Lambda` arm carried zero
18/// construction sites (Pass-1 R1) and was excised; W10 may re-introduce it
19/// behind profiling if the boxed dispatch shows up hot.
20pub enum ConstraintEnum<D: Domain> {
21    NotEqual(NotEqual),
22    AllDifferent(AllDifferent),
23    AllDifferentExcept(AllDifferentExcept<D::Value>),
24    Soft(SoftLambdaConstraint<D>),
25    Custom(Box<dyn Constraint<D>>),
26}
27
28impl<D: Domain> std::fmt::Debug for ConstraintEnum<D> {
29    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
30        match self {
31            Self::NotEqual(c) => c.fmt(f),
32            Self::AllDifferent(c) => c.fmt(f),
33            Self::AllDifferentExcept(c) => c.fmt(f),
34            Self::Soft(c) => c.fmt(f),
35            Self::Custom(c) => c.fmt(f),
36        }
37    }
38}
39
40impl<D: Domain> ConstraintEnum<D>
41where
42    D::Value: PartialEq,
43{
44    #[inline]
45    pub fn scope(&self) -> &[VarId] {
46        match self {
47            Self::NotEqual(c) => &c.scope,
48            Self::AllDifferent(c) => &c.scope,
49            Self::AllDifferentExcept(c) => &c.scope,
50            Self::Soft(c) => &c.scope,
51            Self::Custom(c) => c.scope(),
52        }
53    }
54
55    #[inline]
56    pub fn check(&self, assignment: &[Option<D::Value>]) -> bool {
57        match self {
58            Self::NotEqual(c) => c.check_impl(assignment),
59            Self::AllDifferent(c) => c.check_impl(assignment),
60            Self::AllDifferentExcept(c) => c.check_impl(assignment),
61            Self::Soft(_) => true, // soft constraints never reject
62            Self::Custom(c) => c.check(assignment),
63        }
64    }
65
66    /// For soft constraints, compute the penalty if the underlying predicate
67    /// is violated. Returns 0.0 for hard constraints or satisfied soft constraints.
68    #[inline]
69    pub fn soft_penalty(&self, assignment: &[Option<D::Value>]) -> f64 {
70        match self {
71            Self::Soft(c) => {
72                if c.is_satisfied(assignment) {
73                    0.0
74                } else {
75                    c.penalty
76                }
77            }
78            _ => 0.0,
79        }
80    }
81}
82
83impl<D: Domain> ConstraintEnum<D>
84where
85    D::Value: PartialEq + 'static,
86{
87    #[inline]
88    pub fn revise(&self, vars: &mut [Variable<D>], depth: usize) -> Revision {
89        match self {
90            Self::NotEqual(c) => c.revise_impl(vars, depth),
91            Self::AllDifferent(c) => c.revise_impl(vars, depth),
92            Self::AllDifferentExcept(c) => c.revise_impl(vars, depth),
93            Self::Soft(_) => Revision::Unchanged, // soft constraints don't prune
94            Self::Custom(c) => c.revise(vars, depth),
95        }
96    }
97}
csp_solver/constraint/dispatch.rs

csp_solver/constraint/
dispatch.rs
