solverforge_solver/phase/construction/
placer.rs

1/* Entity placers for construction heuristic
2
3Placers enumerate the entities that need values assigned and
4generate candidate moves for each entity.
5*/
6
7use std::fmt::Debug;
8use std::marker::PhantomData;
9
10use solverforge_core::domain::PlanningSolution;
11use solverforge_scoring::Director;
12
13use crate::heuristic::r#move::{ChangeMove, Move};
14use crate::heuristic::selector::{EntityReference, EntitySelector, ValueSelector};
15
16use super::ConstructionSlotId;
17
18/// A placement represents an entity that needs a value assigned,
19/// along with the candidate moves to assign values.
20///
21/// # Type Parameters
22/// * `S` - The planning solution type
23/// * `M` - The move type
24pub struct Placement<S, M>
25where
26    S: PlanningSolution,
27    M: Move<S>,
28{
29    // The entity reference.
30    pub entity_ref: EntityReference,
31    // Candidate moves for this placement.
32    pub moves: Vec<M>,
33    // Whether keeping the current value is a legal construction choice.
34    keep_current_legal: bool,
35    slot_id: Option<ConstructionSlotId>,
36    _phantom: PhantomData<fn() -> S>,
37}
38
39impl<S, M> Placement<S, M>
40where
41    S: PlanningSolution,
42    M: Move<S>,
43{
44    pub fn new(entity_ref: EntityReference, moves: Vec<M>) -> Self {
45        Self {
46            entity_ref,
47            moves,
48            keep_current_legal: false,
49            slot_id: None,
50            _phantom: PhantomData,
51        }
52    }
53
54    pub fn is_empty(&self) -> bool {
55        self.moves.is_empty()
56    }
57
58    pub fn with_keep_current_legal(mut self, legal: bool) -> Self {
59        self.keep_current_legal = legal;
60        self
61    }
62
63    pub fn keep_current_legal(&self) -> bool {
64        self.keep_current_legal
65    }
66
67    pub(crate) fn with_slot_id(mut self, slot_id: ConstructionSlotId) -> Self {
68        self.slot_id = Some(slot_id);
69        self
70    }
71
72    pub(crate) fn slot_id(&self) -> Option<ConstructionSlotId> {
73        self.slot_id
74    }
75
76    /// Takes ownership of a move at the given index.
77    ///
78    /// Uses swap_remove for O(1) removal.
79    pub fn take_move(&mut self, index: usize) -> M {
80        self.moves.swap_remove(index)
81    }
82}
83
84impl<S, M> Debug for Placement<S, M>
85where
86    S: PlanningSolution,
87    M: Move<S>,
88{
89    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
90        f.debug_struct("Placement")
91            .field("entity_ref", &self.entity_ref)
92            .field("move_count", &self.moves.len())
93            .field("keep_current_legal", &self.keep_current_legal)
94            .field("slot_id", &self.slot_id)
95            .finish()
96    }
97}
98
99/// Trait for placing entities during construction.
100///
101/// Entity placers iterate over uninitialized entities and generate
102/// candidate moves for each.
103///
104/// # Type Parameters
105/// * `S` - The planning solution type
106/// * `M` - The move type
107pub trait EntityPlacer<S, M>: Send + Debug
108where
109    S: PlanningSolution,
110    M: Move<S>,
111{
112    // Returns all placements (entities + their candidate moves).
113    fn get_placements<D: Director<S>>(&self, score_director: &D) -> Vec<Placement<S, M>>;
114}
115
116/// A queued entity placer that processes entities in order.
117///
118/// For each uninitialized entity, generates change moves for all possible values.
119/// Uses typed function pointers for zero-erasure access.
120///
121/// # Type Parameters
122/// * `S` - The planning solution type
123/// * `V` - The value type
124/// * `ES` - The entity selector type
125/// * `VS` - The value selector type
126pub struct QueuedEntityPlacer<S, V, ES, VS>
127where
128    S: PlanningSolution,
129    ES: EntitySelector<S>,
130    VS: ValueSelector<S, V>,
131{
132    // The entity selector.
133    entity_selector: ES,
134    // The value selector.
135    value_selector: VS,
136    // Typed getter function pointer.
137    getter: fn(&S, usize, usize) -> Option<V>,
138    // Typed setter function pointer.
139    setter: fn(&mut S, usize, usize, Option<V>),
140    variable_index: usize,
141    // The variable name.
142    variable_name: &'static str,
143    // The descriptor index.
144    descriptor_index: usize,
145    // Whether the variable can remain unassigned during construction.
146    allows_unassigned: bool,
147    _phantom: PhantomData<fn() -> V>,
148}
149
150impl<S, V, ES, VS> QueuedEntityPlacer<S, V, ES, VS>
151where
152    S: PlanningSolution,
153    ES: EntitySelector<S>,
154    VS: ValueSelector<S, V>,
155{
156    pub fn new(
157        entity_selector: ES,
158        value_selector: VS,
159        getter: fn(&S, usize, usize) -> Option<V>,
160        setter: fn(&mut S, usize, usize, Option<V>),
161        descriptor_index: usize,
162        variable_index: usize,
163        variable_name: &'static str,
164    ) -> Self {
165        Self {
166            entity_selector,
167            value_selector,
168            getter,
169            setter,
170            variable_index,
171            variable_name,
172            descriptor_index,
173            allows_unassigned: false,
174            _phantom: PhantomData,
175        }
176    }
177
178    pub fn with_allows_unassigned(mut self, allows_unassigned: bool) -> Self {
179        self.allows_unassigned = allows_unassigned;
180        self
181    }
182}
183
184impl<S, V, ES, VS> Debug for QueuedEntityPlacer<S, V, ES, VS>
185where
186    S: PlanningSolution,
187    ES: EntitySelector<S> + Debug,
188    VS: ValueSelector<S, V> + Debug,
189{
190    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
191        f.debug_struct("QueuedEntityPlacer")
192            .field("entity_selector", &self.entity_selector)
193            .field("value_selector", &self.value_selector)
194            .field("variable_name", &self.variable_name)
195            .field("allows_unassigned", &self.allows_unassigned)
196            .finish()
197    }
198}
199
200impl<S, V, ES, VS> EntityPlacer<S, ChangeMove<S, V>> for QueuedEntityPlacer<S, V, ES, VS>
201where
202    S: PlanningSolution,
203    V: Clone + PartialEq + Send + Sync + Debug + 'static,
204    ES: EntitySelector<S>,
205    VS: ValueSelector<S, V>,
206{
207    fn get_placements<D: Director<S>>(
208        &self,
209        score_director: &D,
210    ) -> Vec<Placement<S, ChangeMove<S, V>>> {
211        let variable_name = self.variable_name;
212        let descriptor_index = self.descriptor_index;
213        let getter = self.getter;
214        let setter = self.setter;
215        let variable_index = self.variable_index;
216        let allows_unassigned = self.allows_unassigned;
217
218        self.entity_selector
219            .iter(score_director)
220            .filter_map(|entity_ref| {
221                // Check if entity is uninitialized using typed getter - zero erasure
222                let current_value = getter(
223                    score_director.working_solution(),
224                    entity_ref.entity_index,
225                    variable_index,
226                );
227
228                // Only include uninitialized entities
229                if current_value.is_some() {
230                    return None;
231                }
232
233                // Generate moves for all possible values
234                let moves: Vec<ChangeMove<S, V>> = self
235                    .value_selector
236                    .iter(
237                        score_director,
238                        entity_ref.descriptor_index,
239                        entity_ref.entity_index,
240                    )
241                    .map(|value| {
242                        ChangeMove::new(
243                            entity_ref.entity_index,
244                            Some(value),
245                            getter,
246                            setter,
247                            variable_index,
248                            variable_name,
249                            descriptor_index,
250                        )
251                    })
252                    .collect();
253
254                if moves.is_empty() {
255                    None
256                } else {
257                    Some(
258                        Placement::new(entity_ref, moves)
259                            .with_keep_current_legal(allows_unassigned),
260                    )
261                }
262            })
263            .collect()
264    }
265}
266
267/// Entity placer that sorts placements by a comparator function.
268///
269/// Wraps an inner placer and sorts its placements using a typed comparator.
270/// This enables FIRST_FIT_DECREASING and similar construction variants.
271///
272/// # Example
273///
274/// ```
275/// use solverforge_solver::phase::construction::{SortedEntityPlacer, QueuedEntityPlacer, EntityPlacer};
276/// use solverforge_solver::heuristic::r#move::ChangeMove;
277/// use solverforge_solver::heuristic::selector::{FromSolutionEntitySelector, StaticValueSelector};
278/// use solverforge_core::domain::PlanningSolution;
279/// use solverforge_core::score::SoftScore;
280/// use solverforge_scoring::ScoreDirector;
281/// use std::cmp::Ordering;
282///
283/// #[derive(Clone, Debug)]
284/// struct Task { difficulty: i32, assigned: Option<i32> }
285///
286/// #[derive(Clone, Debug)]
287/// struct Solution { tasks: Vec<Task>, score: Option<SoftScore> }
288///
289/// impl PlanningSolution for Solution {
290///     type Score = SoftScore;
291///     fn score(&self) -> Option<Self::Score> { self.score }
292///     fn set_score(&mut self, score: Option<Self::Score>) { self.score = score; }
293/// }
294///
295/// fn get_assigned(s: &Solution, i: usize) -> Option<i32> {
296///     s.tasks.get(i).and_then(|t| t.assigned)
297/// }
298/// fn set_assigned(s: &mut Solution, i: usize, v: Option<i32>) {
299///     if let Some(t) = s.tasks.get_mut(i) { t.assigned = v; }
300/// }
301///
302/// // Sort entities by difficulty (descending) for FIRST_FIT_DECREASING
303/// fn difficulty_descending(s: &Solution, a: usize, b: usize) -> Ordering {
304///     let da = s.tasks.get(a).map(|t| t.difficulty).unwrap_or(0);
305///     let db = s.tasks.get(b).map(|t| t.difficulty).unwrap_or(0);
306///     db.cmp(&da)  // Descending order
307/// }
308/// ```
309pub struct SortedEntityPlacer<S, M, Inner>
310where
311    S: PlanningSolution,
312    M: Move<S>,
313    Inner: EntityPlacer<S, M>,
314{
315    inner: Inner,
316    // Comparator function: takes (solution, entity_index_a, entity_index_b) -> Ordering
317    comparator: fn(&S, usize, usize) -> std::cmp::Ordering,
318    _phantom: PhantomData<fn() -> (S, M)>,
319}
320
321impl<S, M, Inner> SortedEntityPlacer<S, M, Inner>
322where
323    S: PlanningSolution,
324    M: Move<S>,
325    Inner: EntityPlacer<S, M>,
326{
327    /// Creates a new sorted entity placer.
328    ///
329    /// # Arguments
330    /// * `inner` - The inner placer to wrap
331    /// * `comparator` - Function to compare entities: `(solution, idx_a, idx_b) -> Ordering`
332    pub fn new(inner: Inner, comparator: fn(&S, usize, usize) -> std::cmp::Ordering) -> Self {
333        Self {
334            inner,
335            comparator,
336            _phantom: PhantomData,
337        }
338    }
339}
340
341impl<S, M, Inner> Debug for SortedEntityPlacer<S, M, Inner>
342where
343    S: PlanningSolution,
344    M: Move<S>,
345    Inner: EntityPlacer<S, M>,
346{
347    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
348        f.debug_struct("SortedEntityPlacer")
349            .field("inner", &self.inner)
350            .finish()
351    }
352}
353
354impl<S, M, Inner> EntityPlacer<S, M> for SortedEntityPlacer<S, M, Inner>
355where
356    S: PlanningSolution,
357    M: Move<S>,
358    Inner: EntityPlacer<S, M>,
359{
360    fn get_placements<D: Director<S>>(&self, score_director: &D) -> Vec<Placement<S, M>> {
361        let mut placements = self.inner.get_placements(score_director);
362        let solution = score_director.working_solution();
363        let cmp = self.comparator;
364
365        placements.sort_by(|a, b| {
366            cmp(
367                solution,
368                a.entity_ref.entity_index,
369                b.entity_ref.entity_index,
370            )
371        });
372
373        placements
374    }
375}
376
377#[cfg(test)]
378mod tests;
solverforge_solver/phase/construction/placer.rs

solverforge_solver/phase/construction/
placer.rs
