rayon/iter/
fold.rs

1use super::plumbing::*;
2use super::*;
3
4use std::fmt::{self, Debug};
5
6impl<I, ID, F> Fold<I, ID, F> {
7    pub(super) fn new(base: I, identity: ID, fold_op: F) -> Self {
8        Fold {
9            base,
10            identity,
11            fold_op,
12        }
13    }
14}
15
16/// `Fold` is an iterator that applies a function over an iterator producing a single value.
17/// This struct is created by the [`fold()`] method on [`ParallelIterator`]
18///
19/// [`fold()`]: ParallelIterator::fold()
20#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
21#[derive(Clone)]
22pub struct Fold<I, ID, F> {
23    base: I,
24    identity: ID,
25    fold_op: F,
26}
27
28impl<I: Debug, ID, F> Debug for Fold<I, ID, F> {
29    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
30        f.debug_struct("Fold").field("base", &self.base).finish()
31    }
32}
33
34impl<U, I, ID, F> ParallelIterator for Fold<I, ID, F>
35where
36    I: ParallelIterator,
37    F: Fn(U, I::Item) -> U + Sync + Send,
38    ID: Fn() -> U + Sync + Send,
39    U: Send,
40{
41    type Item = U;
42
43    fn drive_unindexed<C>(self, consumer: C) -> C::Result
44    where
45        C: UnindexedConsumer<Self::Item>,
46    {
47        let consumer1 = FoldConsumer {
48            base: consumer,
49            fold_op: &self.fold_op,
50            identity: &self.identity,
51        };
52        self.base.drive_unindexed(consumer1)
53    }
54}
55
56struct FoldConsumer<'c, C, ID, F> {
57    base: C,
58    fold_op: &'c F,
59    identity: &'c ID,
60}
61
62impl<'r, U, T, C, ID, F> Consumer<T> for FoldConsumer<'r, C, ID, F>
63where
64    C: Consumer<U>,
65    F: Fn(U, T) -> U + Sync,
66    ID: Fn() -> U + Sync,
67    U: Send,
68{
69    type Folder = FoldFolder<'r, C::Folder, U, F>;
70    type Reducer = C::Reducer;
71    type Result = C::Result;
72
73    fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
74        let (left, right, reducer) = self.base.split_at(index);
75        (
76            FoldConsumer { base: left, ..self },
77            FoldConsumer {
78                base: right,
79                ..self
80            },
81            reducer,
82        )
83    }
84
85    fn into_folder(self) -> Self::Folder {
86        FoldFolder {
87            base: self.base.into_folder(),
88            item: (self.identity)(),
89            fold_op: self.fold_op,
90        }
91    }
92
93    fn full(&self) -> bool {
94        self.base.full()
95    }
96}
97
98impl<'r, U, T, C, ID, F> UnindexedConsumer<T> for FoldConsumer<'r, C, ID, F>
99where
100    C: UnindexedConsumer<U>,
101    F: Fn(U, T) -> U + Sync,
102    ID: Fn() -> U + Sync,
103    U: Send,
104{
105    fn split_off_left(&self) -> Self {
106        FoldConsumer {
107            base: self.base.split_off_left(),
108            ..*self
109        }
110    }
111
112    fn to_reducer(&self) -> Self::Reducer {
113        self.base.to_reducer()
114    }
115}
116
117struct FoldFolder<'r, C, ID, F> {
118    base: C,
119    fold_op: &'r F,
120    item: ID,
121}
122
123impl<'r, C, ID, F, T> Folder<T> for FoldFolder<'r, C, ID, F>
124where
125    C: Folder<ID>,
126    F: Fn(ID, T) -> ID + Sync,
127{
128    type Result = C::Result;
129
130    fn consume(self, item: T) -> Self {
131        let item = (self.fold_op)(self.item, item);
132        FoldFolder {
133            base: self.base,
134            fold_op: self.fold_op,
135            item,
136        }
137    }
138
139    fn consume_iter<I>(self, iter: I) -> Self
140    where
141        I: IntoIterator<Item = T>,
142    {
143        fn not_full<C, ID, T>(base: &C) -> impl Fn(&T) -> bool + '_
144        where
145            C: Folder<ID>,
146        {
147            move |_| !base.full()
148        }
149
150        let base = self.base;
151        let item = iter
152            .into_iter()
153            // stop iterating if another thread has finished
154            .take_while(not_full(&base))
155            .fold(self.item, self.fold_op);
156
157        FoldFolder {
158            base,
159            item,
160            fold_op: self.fold_op,
161        }
162    }
163
164    fn complete(self) -> C::Result {
165        self.base.consume(self.item).complete()
166    }
167
168    fn full(&self) -> bool {
169        self.base.full()
170    }
171}
172
173// ///////////////////////////////////////////////////////////////////////////
174
175impl<I, U, F> FoldWith<I, U, F> {
176    pub(super) fn new(base: I, item: U, fold_op: F) -> Self {
177        FoldWith {
178            base,
179            item,
180            fold_op,
181        }
182    }
183}
184
185/// `FoldWith` is an iterator that applies a function over an iterator producing a single value.
186/// This struct is created by the [`fold_with()`] method on [`ParallelIterator`]
187///
188/// [`fold_with()`]: ParallelIterator::fold_with()
189#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
190#[derive(Clone)]
191pub struct FoldWith<I, U, F> {
192    base: I,
193    item: U,
194    fold_op: F,
195}
196
197impl<I: Debug, U: Debug, F> Debug for FoldWith<I, U, F> {
198    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
199        f.debug_struct("FoldWith")
200            .field("base", &self.base)
201            .field("item", &self.item)
202            .finish()
203    }
204}
205
206impl<U, I, F> ParallelIterator for FoldWith<I, U, F>
207where
208    I: ParallelIterator,
209    F: Fn(U, I::Item) -> U + Sync + Send,
210    U: Send + Clone,
211{
212    type Item = U;
213
214    fn drive_unindexed<C>(self, consumer: C) -> C::Result
215    where
216        C: UnindexedConsumer<Self::Item>,
217    {
218        let consumer1 = FoldWithConsumer {
219            base: consumer,
220            item: self.item,
221            fold_op: &self.fold_op,
222        };
223        self.base.drive_unindexed(consumer1)
224    }
225}
226
227struct FoldWithConsumer<'c, C, U, F> {
228    base: C,
229    item: U,
230    fold_op: &'c F,
231}
232
233impl<'r, U, T, C, F> Consumer<T> for FoldWithConsumer<'r, C, U, F>
234where
235    C: Consumer<U>,
236    F: Fn(U, T) -> U + Sync,
237    U: Send + Clone,
238{
239    type Folder = FoldFolder<'r, C::Folder, U, F>;
240    type Reducer = C::Reducer;
241    type Result = C::Result;
242
243    fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
244        let (left, right, reducer) = self.base.split_at(index);
245        (
246            FoldWithConsumer {
247                base: left,
248                item: self.item.clone(),
249                ..self
250            },
251            FoldWithConsumer {
252                base: right,
253                ..self
254            },
255            reducer,
256        )
257    }
258
259    fn into_folder(self) -> Self::Folder {
260        FoldFolder {
261            base: self.base.into_folder(),
262            item: self.item,
263            fold_op: self.fold_op,
264        }
265    }
266
267    fn full(&self) -> bool {
268        self.base.full()
269    }
270}
271
272impl<'r, U, T, C, F> UnindexedConsumer<T> for FoldWithConsumer<'r, C, U, F>
273where
274    C: UnindexedConsumer<U>,
275    F: Fn(U, T) -> U + Sync,
276    U: Send + Clone,
277{
278    fn split_off_left(&self) -> Self {
279        FoldWithConsumer {
280            base: self.base.split_off_left(),
281            item: self.item.clone(),
282            ..*self
283        }
284    }
285
286    fn to_reducer(&self) -> Self::Reducer {
287        self.base.to_reducer()
288    }
289}
rayon/iter/fold.rs

rayon/iter/
fold.rs
