1 | use super::plumbing::*; |
2 | use super::ParallelIterator; |
3 | |
4 | use std::iter::{self, Sum}; |
5 | use std::marker::PhantomData; |
6 | |
7 | pub(super) fn sum<PI, S>(pi: PI) -> S |
8 | where |
9 | PI: ParallelIterator, |
10 | S: Send + Sum<PI::Item> + Sum, |
11 | { |
12 | pi.drive_unindexed(SumConsumer::new()) |
13 | } |
14 | |
15 | fn add<T: Sum>(left: T, right: T) -> T { |
16 | [left, right].into_iter().sum() |
17 | } |
18 | |
19 | struct SumConsumer<S: Send> { |
20 | _marker: PhantomData<*const S>, |
21 | } |
22 | |
23 | unsafe impl<S: Send> Send for SumConsumer<S> {} |
24 | |
25 | impl<S: Send> SumConsumer<S> { |
26 | fn new() -> SumConsumer<S> { |
27 | SumConsumer { |
28 | _marker: PhantomData, |
29 | } |
30 | } |
31 | } |
32 | |
33 | impl<S, T> Consumer<T> for SumConsumer<S> |
34 | where |
35 | S: Send + Sum<T> + Sum, |
36 | { |
37 | type Folder = SumFolder<S>; |
38 | type Reducer = Self; |
39 | type Result = S; |
40 | |
41 | fn split_at(self, _index: usize) -> (Self, Self, Self) { |
42 | (SumConsumer::new(), SumConsumer::new(), SumConsumer::new()) |
43 | } |
44 | |
45 | fn into_folder(self) -> Self::Folder { |
46 | SumFolder { |
47 | sum: iter::empty::<T>().sum(), |
48 | } |
49 | } |
50 | |
51 | fn full(&self) -> bool { |
52 | false |
53 | } |
54 | } |
55 | |
56 | impl<S, T> UnindexedConsumer<T> for SumConsumer<S> |
57 | where |
58 | S: Send + Sum<T> + Sum, |
59 | { |
60 | fn split_off_left(&self) -> Self { |
61 | SumConsumer::new() |
62 | } |
63 | |
64 | fn to_reducer(&self) -> Self::Reducer { |
65 | SumConsumer::new() |
66 | } |
67 | } |
68 | |
69 | impl<S> Reducer<S> for SumConsumer<S> |
70 | where |
71 | S: Send + Sum, |
72 | { |
73 | fn reduce(self, left: S, right: S) -> S { |
74 | add(left, right) |
75 | } |
76 | } |
77 | |
78 | struct SumFolder<S> { |
79 | sum: S, |
80 | } |
81 | |
82 | impl<S, T> Folder<T> for SumFolder<S> |
83 | where |
84 | S: Sum<T> + Sum, |
85 | { |
86 | type Result = S; |
87 | |
88 | fn consume(self, item: T) -> Self { |
89 | SumFolder { |
90 | sum: add(self.sum, iter::once(item).sum()), |
91 | } |
92 | } |
93 | |
94 | fn consume_iter<I>(self, iter: I) -> Self |
95 | where |
96 | I: IntoIterator<Item = T>, |
97 | { |
98 | SumFolder { |
99 | sum: add(self.sum, iter.into_iter().sum()), |
100 | } |
101 | } |
102 | |
103 | fn complete(self) -> S { |
104 | self.sum |
105 | } |
106 | |
107 | fn full(&self) -> bool { |
108 | false |
109 | } |
110 | } |
111 | |