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
140
141
142
143
144
145
|
// Copyright (c) 2014-2016, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#pragma once
#include <boost/optional/optional.hpp>
#include <boost/thread/condition_variable.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/thread.hpp>
#include <cstddef>
#include <functional>
#include <thread>
#include <utility>
#include <vector>
namespace tools
{
//! Manages zero or more threads for work dispatching.
class thread_group
{
public:
//! \return `get_max_concurrency() ? get_max_concurrency() - 1 : 0`
static std::size_t optimal();
//! \return `count ? min(count - 1, optimal()) : 0`
static std::size_t optimal_with_max(std::size_t count);
//! Create an optimal number of threads.
explicit thread_group() : thread_group(optimal()) {}
//! Create exactly `count` threads.
explicit thread_group(std::size_t count);
thread_group(thread_group const&) = delete;
thread_group(thread_group&&) = delete;
//! Joins threads, but does not necessarily run all dispatched functions.
~thread_group() = default;
thread_group& operator=(thread_group const&) = delete;
thread_group& operator=(thread_group&&) = delete;
//! \return Number of threads owned by `this` group.
std::size_t count() const noexcept {
if (internal) {
return internal->count();
}
return 0;
}
//! \return True iff a function was available and executed (on `this_thread`).
bool try_run_one() noexcept {
if (internal) {
return internal->try_run_one();
}
return false;
}
/*! `f` is invoked immediately if `count() == 0`, otherwise execution of `f`
is queued for next available thread. If `f` is queued, any exception leaving
that function will result in process termination. Use std::packaged_task if
exceptions need to be handled. */
template<typename F>
void dispatch(F&& f) {
if (internal) {
internal->dispatch(std::forward<F>(f));
}
else {
f();
}
}
private:
class data {
public:
data(std::size_t count);
~data() noexcept;
std::size_t count() const noexcept {
return threads.size();
}
bool try_run_one() noexcept;
void dispatch(std::function<void()> f);
private:
struct work;
struct node {
node() = delete;
std::unique_ptr<work> ptr;
};
struct work {
work() = delete;
std::function<void()> f;
node next;
};
//! Requires lock on `mutex`.
std::unique_ptr<work> get_next() noexcept;
//! Blocks until destructor is invoked, only call from thread.
void run() noexcept;
private:
std::vector<boost::thread> threads;
node head;
node* last;
boost::condition_variable has_work;
boost::mutex mutex;
bool stop;
};
private:
// optionally construct elements, without separate heap allocation
boost::optional<data> internal;
};
}
|
