1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139

pub use self::actual::map_reduce;
pub use self::actual::parallel_collect;
pub use self::actual::parallel_foreach_mut;
pub use self::actual::parallel_into_collect;
pub use self::actual::ThreadPool;

#[cfg(not(target_arch = "wasm32"))]
mod actual {
    extern crate rayon;
    use self::rayon::{ThreadPool as RayonThreadPool, ThreadPoolBuilder};
    use rayon::prelude::*;

    /// Represents a thread pool wrapper.
    pub struct ThreadPool {
        inner: RayonThreadPool,
    }

    impl ThreadPool {
        /// Creates a new instance of `ThreadPool`
        pub fn new(num_threads: usize) -> Self {
            Self {
                inner: ThreadPoolBuilder::new().num_threads(num_threads).build().expect("cannot build a thread pool"),
            }
        }

        /// Executes given operation on thread pool.
        pub fn execute<OP, R>(&self, op: OP) -> R
        where
            OP: FnOnce() -> R + Send,
            R: Send,
        {
            self.inner.install(op)
        }
    }

    /// Maps collection and collects results into vector in parallel.
    pub fn parallel_collect<T, F, R>(source: &[T], map_op: F) -> Vec<R>
    where
        T: Send + Sync,
        F: Fn(&T) -> R + Sync + Send,
        R: Send,
    {
        source.par_iter().map(map_op).collect()
    }

    /// Maps collection and collects results into vector in parallel.
    pub fn parallel_into_collect<T, F, R>(source: Vec<T>, map_op: F) -> Vec<R>
    where
        T: Send + Sync,
        F: Fn(T) -> R + Sync + Send,
        R: Send,
    {
        source.into_par_iter().map(map_op).collect()
    }

    /// Performs map reduce operations in parallel.
    pub fn map_reduce<T, FM, FR, FD, R>(source: &[T], map_op: FM, default_op: FD, reduce_op: FR) -> R
    where
        T: Send + Sync,
        FM: Fn(&T) -> R + Sync + Send,
        FR: Fn(R, R) -> R + Sync + Send,
        FD: Fn() -> R + Sync + Send,
        R: Send,
    {
        source.par_iter().map(map_op).reduce(default_op, reduce_op)
    }

    /// Performs mutable foreach in parallel.
    pub fn parallel_foreach_mut<T, F>(source: &mut [T], action: F)
    where
        T: Send + Sync,
        F: Fn(&mut T) + Send + Sync,
    {
        source.par_iter_mut().for_each(action)
    }
}

#[cfg(target_arch = "wasm32")]
mod actual {
    /// Represents a thread pool wrapper.
    pub struct ThreadPool;

    impl ThreadPool {
        /// Creates a new instance of `ThreadPool`.
        pub fn new(_num_threads: usize) -> Self {
            Self {}
        }

        /// Executes given operation on thread pool (dummy).
        pub fn execute<OP, R>(&self, op: OP) -> R
        where
            OP: FnOnce() -> R + Send,
            R: Send,
        {
            op()
        }
    }

    /// Map collections and collects results into vector synchronously.
    pub fn parallel_collect<T, F, R>(source: &[T], map_op: F) -> Vec<R>
    where
        T: Send + Sync,
        F: Fn(&T) -> R + Sync + Send,
        R: Send,
    {
        source.iter().map(map_op).collect()
    }

    /// Map collections and collects results into vector synchronously.
    pub fn parallel_into_collect<T, F, R>(source: Vec<T>, map_op: F) -> Vec<R>
    where
        T: Send + Sync,
        F: Fn(T) -> R + Sync + Send,
        R: Send,
    {
        source.into_iter().map(map_op).collect()
    }

    /// Performs map reduce operations synchronously.
    pub fn map_reduce<T, FM, FR, FD, R>(source: &[T], map_op: FM, default_op: FD, reduce_op: FR) -> R
    where
        T: Send + Sync,
        FM: Fn(&T) -> R + Sync + Send,
        FR: Fn(R, R) -> R + Sync + Send,
        FD: Fn() -> R + Sync + Send,
        R: Send,
    {
        source.iter().map(map_op).fold(default_op(), reduce_op)
    }

    /// Performs mutable foreach in parallel.
    pub fn parallel_foreach_mut<T, F>(source: &mut [T], action: F)
    where
        T: Send + Sync,
        F: Fn(&mut T) + Send + Sync,
    {
        source.iter_mut().for_each(action)
    }
}