├── .gitignore
├── CMakeLists.txt
├── LICENSE
├── README.md
├── affinity.patch
├── example
└── main.cpp
└── include
├── SafeQueue.h
└── ThreadPool.h
/.gitignore:
--------------------------------------------------------------------------------
1 | # Build
2 | #VS
3 | .vs/
4 | Debug/
5 | Release/
6 | # Netbeans
7 | nbproject/
8 | *.user
9 | *.filters
10 | *.vcxproj
11 | *.sln
12 |
13 | # Cmake
14 | build
15 | CMakeCache.txt
16 | CMakeFiles
17 | CMakeScripts
18 | Makefile
19 | cmake_install.cmake
20 | install_manifest.txt
21 | CTestTestfile.cmake
22 |
23 | # Compiled Object files
24 | *.slo
25 | *.lo
26 | *.o
27 | *.obj
28 | !assets/models/*/*.obj
29 |
30 | # Precompiled Headers
31 | *.gch
32 | *.pch
33 |
34 | # Compiled Dynamic libraries
35 | *.so
36 | *.dylib
37 | *.dll
38 |
39 | # Fortran module files
40 | *.mod
41 | *.smod
42 |
43 | # Compiled Static libraries
44 | *.lai
45 | *.la
46 | *.a
47 | *.lib
48 |
49 | # Executables
50 | *.exe
51 | *.out
52 | *.app
53 |
--------------------------------------------------------------------------------
/CMakeLists.txt:
--------------------------------------------------------------------------------
1 | # CMake entry point
2 | cmake_minimum_required (VERSION 3.5)
3 | project (thread-pool)
4 |
5 | ## Add headers files
6 | include_directories (
7 | include/
8 | )
9 |
10 | set(HEADERS include/SafeQueue.h include/ThreadPool.h)
11 |
12 | set(SOURCES example/main.cpp)
13 |
14 | SET(CMAKE_CXX_FLAGS -pthread)
15 |
16 | add_compile_options(
17 | -std=c++11
18 | # -D_DEBUG
19 | # -g
20 | )
21 |
22 | # main.cpp
23 | add_executable(main ${HEADERS} ${SOURCES})
24 | target_link_libraries(main)
25 |
--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
1 | MIT License
2 |
3 | Copyright (c) 2016 Mariano Trebino
4 |
5 | Permission is hereby granted, free of charge, to any person obtaining a copy
6 | of this software and associated documentation files (the "Software"), to deal
7 | in the Software without restriction, including without limitation the rights
8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 |
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 |
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 |
--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
1 | # Table of Contents
2 | [Introduction](https://github.com/mtrebi/thread-pool/blob/master/README.md#introduction)
3 | [Build instructions](https://github.com/mtrebi/thread-pool/blob/master/README.md#build-instructions)
4 | [Thread pool](https://github.com/mtrebi/thread-pool/blob/master/README.md#thread-pool)
5 | [Queue](https://github.com/mtrebi/thread-pool/blob/master/README.md#queue)
6 | [Submit function](https://github.com/mtrebi/thread-pool/blob/master/README.md#submit-function)
7 | [Thread worker](https://github.com/mtrebi/thread-pool/blob/master/README.md#thread-worker)
8 | [Usage example](https://github.com/mtrebi/thread-pool/blob/master/README.md#usage-example)
9 | [Use case#1](https://github.com/mtrebi/thread-pool#use-case-1)
10 | [Use case#2](https://github.com/mtrebi/thread-pool#use-case-2)
11 | [Use case#3](https://github.com/mtrebi/thread-pool#use-case-3)
12 | [Future work](https://github.com/mtrebi/thread-pool/blob/master/README.md#future-work)
13 | [References](https://github.com/mtrebi/thread-pool/blob/master/README.md#references)
14 |
15 | # Introduction:
16 |
17 | A [thread pool](https://en.wikipedia.org/wiki/Thread_pool) is a technique that allows developers to exploit the concurrency of modern processors in an **easy** and **efficient** manner. It's easy because you send "work" to the pool and somehow this work gets done without blocking the main thread. It's efficient because threads are not initialized each time we want the work to be done. Threads are initialized once and remain inactive until some work has to be done. This way we minimize the overhead.
18 |
19 | There are many more Thread pool implementations in C++, many of them are probably better (safer, faster...) than mine. However,I believe my implementation are **very straightforward and easy to understand**.
20 |
21 | __Disclaimer: Please Do not use this project in a professional environment. It may contain bugs and/or not work as expected.__ I did this project to learn how C++11 Threads work and provide an easy way for other people to understand it too.
22 |
23 | # Build instructions:
24 |
25 | This project has been developed using Netbeans and Linux but it should work on Windows, MAC OS and Linux. It can be easily build using CMake and different other generators. The following code can be used to generate the VS 2017 project files:
26 |
27 | ```c
28 | // VS 2017
29 | cd
30 | mkdir build
31 | cd build/
32 | cmake .. "Visual Studio 15 2017 Win64"
33 | ```
34 |
35 | Then, from VS you can edit and execute the project. Make sure that __main project is set up as the startup project__
36 |
37 | If you are using Linux, you need to change the generator (use the default) and execute an extra operation to actually make it executable:
38 |
39 | ```c
40 | // Linux
41 | cd
42 | mkdir build
43 | cd build/
44 | cmake ..
45 | make
46 | ```
47 |
48 | # Thread pool
49 |
50 | The way that I understand things better is with images. So, let's take a look at the image of thread pool given by Wikipedia:
51 |
52 | 
53 |
54 | As you can see, we have three important elements here:
55 | * *Tasks Queue*. This is where the work that has to be done is stored.
56 | * *Thread Pool*. This is set of threads (or workers) that continuously take work from the queue and do it.
57 | * *Completed Tasks*. When the Thread has finished the work we return "something" to notify that the work has finished.
58 |
59 | ## Queue
60 |
61 | We use a queue to store the work because it's the more sensible data structure. We want the work to be **started** in the same order that we sent it. However, this queue is a little bit **special**. As I said in the previous section, threads are continuously (well, not really, but let's assume that they are) querying the queue to ask for work. When there's work available, threads take the work from the queue and do it. What would happen if two threads try to take the same work at the same time? Well, the program would crash.
62 |
63 | To avoid these kinds of problems, I implemented a wrapper over the standard C++ Queue that uses mutex to restrict the concurrent access. Let's see a small sample of the SafeQueue class:
64 |
65 | ```c
66 | void enqueue(T& t) {
67 | std::unique_lock lock(m_mutex);
68 | m_queue.push(t);
69 | }
70 |
71 | ```
72 | To enqueue the first thing we do is lock the mutex to make sure that no one else is accessing the resource. Then, we push the element to the queue. When the lock goes out of scopes it gets automatically released. Easy, huh? This way, we make the Queue thread-safe and thus we don't have to worry many threads accessing and/or modifying it at the same "time".
73 |
74 | ## Submit function
75 |
76 | The most important method of the thread pool is the one responsible of adding work to the queue. I called this method **submit**. It's not difficult to understand how it works but its implementation can seem scary at first. Let's think about **what** should do and after that we will worry about **how** to do it. What:
77 | * Accept any function with any parameters.
78 | * Return "something" immediately to avoid blocking main thread. This returned object should **eventually** contain the result of the operation.
79 |
80 | Cool, let's see **how** we can implement it.
81 |
82 | ### Submit implementation
83 |
84 | The complete submit functions looks like this:
85 |
86 | ```c
87 | // Submit a function to be executed asynchronously by the pool
88 | template
89 | auto submit(F&& f, Args&&... args) -> std::future {
90 | // Create a function with bounded parameters ready to execute
91 | std::function func = std::bind(std::forward(f), std::forward(args)...);
92 | // Encapsulate it into a shared ptr in order to be able to copy construct / assign
93 | auto task_ptr = std::make_shared>(func);
94 |
95 | // Wrap packaged task into void function
96 | std::function wrapper_func = [task_ptr]() {
97 | (*task_ptr)();
98 | };
99 |
100 | // Enqueue generic wrapper function
101 | m_queue.enqueue(wrapperfunc);
102 |
103 | // Wake up one thread if its waiting
104 | m_conditional_lock.notify_one();
105 |
106 | // Return future from promise
107 | return task_ptr->get_future();
108 | }
109 | ```
110 |
111 | Nevertheless, we're going to inspect line by line what's going on in order to fully understand how it works.
112 |
113 | #### Variadic template function
114 |
115 | ```c
116 | template
117 | ```
118 |
119 | This means that the next statement is templated. The first template parameter is called F (our function) and second one is a parameter pack. A parameter pack is a special template parameter that can accept zero or more template arguments. It is, in fact, a way to express a variable number of arguments in a template. A template with at least one parameter pack is called **variadic template**
120 |
121 | Summarizing, we are telling the compiler that our submit function is going to take one generic parameter of type F (our function) and a parameter pack Args (the parameters of the function F).
122 |
123 | #### Function declaration
124 |
125 | ```c
126 | auto submit(F&& f, Args&&... args) -> std::future {
127 | ```
128 |
129 | This may seem weird but, it's not. A function, in fact, can be declared using two different syntaxes. The following is the most well known:
130 |
131 | ```c
132 | return-type identifier ( argument-declarations... )
133 | ```
134 |
135 | But, we can also declare the function like this:
136 |
137 | ```c
138 | auto identifier ( argument-declarations... ) -> return_type
139 | ```
140 |
141 | Why two syntaxes? Well, imagine that you have a function that has a return type that depends on the input parameters of the function. Using the first syntax you can't declare that function without getting a compiler error since you would be using a variable in the return type that has not been declared yet (because the return type declaration goes before the parameters type declaration).
142 |
143 | Using the second syntax you can declare the function to have return type **auto** then, using the -> you can declare the return type depending on the arguments of the functions that have been declared previously.
144 |
145 | Now, let's inspect the parameters of the submit function. When the type of a parameter is declared as **T&&** for some deducted type T that parameter is a **universal reference**. This term was coined by [Scott Meyers](https://isocpp.org/blog/2012/11/universal-references-in-c11-scott-meyers) because **T&&** can also mean r-value reference. However, in the context of type deduction, it means that it can be bound to both l-values and r-values, unlike l-value references that can only be bound to non-const objects (they bind only to modifiable lvalues) and r-value references (they bind only to rvalues).
146 |
147 |
148 | The return type of the function is of type **std::future**. An std::future is a special type that provides a mechanism to access the result of asynchronous operations, in our case, the result of executing a specific function. This makes sense with what we said earlier.
149 |
150 | Finally, the template type of std::future is **decltype(f(args...))**. Decltype is a special C++ keyword that inspects the declared type of an entity or the type and value category of an expression. In our case, we want to know the return type of the function _f_, so we give decltype our generic function _f_ and the parameter pack _args_.
151 |
152 | #### Function body
153 |
154 | ```c
155 | // Create a function with bounded parameters ready to execute
156 | std::function func = std::bind(std::forward(f), std::forward(args)...);
157 | ```
158 |
159 | There are many many things happening here. First of all, the **std::bind(F, Args)** is a function that creates a wrapper for F with the given Args. Caling this wrapper is the same as calling F with the Args that it has been bound. Here, we are simply calling bind with our generic function _f_ and the parameter pack _args_ but using another wrapper **std::forward(t)** for each parameter. This second wrapper is needed to achieve perfect forwarding of universal references.
160 | The result of this bind call is a **std::function**. The std::function is a C++ object that encapsulates a function. It allows you to execute the function as if it were a normal function calling the operator() with the required parameters BUT, because it is an object, you can store it, copy it and move it around. The template type of any std::function is the signature of that function: std::function< return-type (arguments)>. In this case, we already know how to get the return type of this function using decltype. But, what about the arguments? Well, because we bound all arguments _args_ to the function _f_ we just have to add an empty pair of parenthesis that represents an empty list of arguments: **decltype(f(args...))()**.
161 |
162 |
163 | ```c
164 | // Encapsulate it into a shared ptr in order to be able to copy construct / assign
165 | auto task_ptr = std::make_shared>(func);
166 | ```
167 |
168 | The next thing we do is we create a **std::packaged_task(t)**. A packaged_task is a wrapper around a function that can be executed asynchronously. It's result is stored in a shared state inside an std::future object. The templated type T of an std::packaged_task(t) is the type of the function _t_ that is wrapping. Because we said it before, the signature of the function _f_ is **decltype(f(args...))()** that is the same type of the packaged_task. Then, we just wrap again this packaged task inside a **std::shared_ptr** using the initialize function **std::make_shared**.
169 |
170 | ```c
171 | // Wrap packaged task into void function
172 | std::function wrapperfunc = [task_ptr]() {
173 | (*task_ptr)();
174 | };
175 |
176 | ```
177 |
178 | Again, we create a std:.function, but, note that this time its template type is **void()**. Independently of the function _f_ and its parameters _args_ this _wrapperfunc_ the return type will always be **void**. Since all functions _f_ may have different return types, the only way to store them in a container (our Queue) is wrapping them with a generic void function. Here, we are just declaring this _wrapperfunc_ to execute the actual task _taskptr_ that will execute the bound function _func_.
179 |
180 | ```c
181 | // Enqueue generic wrapper function
182 | m_queue.enqueue(wrapperfunc);
183 | ```
184 |
185 | We enqueue this _wrapperfunc_.
186 |
187 | ```c
188 | // Wake up one thread if its waiting
189 | m_conditional_lock.notify_one();
190 | ```
191 |
192 | Before finishing, we wake up one thread in case it is waiting.
193 |
194 | ```c
195 | // Return future from promise
196 | return task_ptr->get_future();
197 | ```
198 |
199 | And finally, we return the future of the packaged_task. Because we are returning the future that is bound to the packaged_task _taskptr_ that, at the same time, is bound with the function _func_, executing this _taskptr_ will automatically update the future. Because we wrapped the execution of the _taskptr_ with a generic wrapper function, is the execution of _wrapperfunc_ that, in fact, updates the future. Aaaaand. since we enqueued this wrapper function, it will be executed by a thread after being dequeued calling the operator().
200 |
201 |
202 | ## Thread worker
203 |
204 | Now that we understand how the submit method works, we're going to focus on how the work gets done. Probably, the simplest implementation of a thread worker could be using polling:
205 |
206 | Loop
207 | If Queue is not empty
208 | Dequeue work
209 | Do it
210 |
211 | This looks alright but it's **not very efficient**. Do you see why? What would happen if there is no work in the Queue? The threads would keep looping and asking all the time: Is the queue empty?
212 |
213 | The more sensible implementation is done by "sleeping" the threads until some work is added to the queue. As we saw before, as soon as we enqueue work, a signal **notify_one()** is sent. This allows us to implement a more efficient algorithm:
214 |
215 | Loop
216 | If Queue is empty
217 | Wait signal
218 | Dequeue work
219 | Do it
220 |
221 | This signal system is implemented in C++ with **conditional variables**. Conditional variables are always bound to a mutex, so I added a mutex to the thread pool class just to manage this. The final code of a worker looks like this:
222 |
223 | ```c
224 | void operator()() {
225 | std::function func;
226 | bool dequeued;
227 | while (!m_pool->m_shutdown) {
228 | {
229 | std::unique_lock lock(m_pool->m_conditional_mutex);
230 | if (m_pool->m_queue.empty()) {
231 | m_pool->m_conditional_lock.wait(lock);
232 | }
233 | dequeued = m_pool->m_queue.dequeue(func);
234 | }
235 | if (dequeued) {
236 | func();
237 | }
238 | }
239 | }
240 |
241 | ```
242 |
243 | The code is really easy to understand so I am not going to explain anything. The only thing to note here is that, _func_ is our wrapper function declared as:
244 |
245 | ```c
246 | std::function wrapperfunc = [task_ptr]() {
247 | (*task_ptr)();
248 | };
249 |
250 | ```
251 |
252 | So, executing this function will automatically update the future.
253 |
254 | # Usage example
255 |
256 | Creating the thread pool is as easy as:
257 |
258 | ```c
259 | // Create pool with 3 threads
260 | ThreadPool pool(3);
261 |
262 | // Initialize pool
263 | pool.init();
264 | ```
265 |
266 | When we want to shutdown the pool just call:
267 |
268 | ```c
269 | // Shutdown the pool, releasing all threads
270 | pool.shutdown()
271 | ```
272 |
273 | Ff we want to send some work to the pool, after we have initialized it, we just have to call the submit function:
274 |
275 | ```c
276 | pool.submit(work);
277 | ```
278 |
279 | Depending on the type of work, I've distinguished different use-cases. Suppose that the work that we have to do is multiply two numbers. We can do it in many different ways. I've implemented the three most common ways to do it that I can imagine:
280 | * Use-Case #1. Function returns the result
281 | * Use-Case #2. Function updates by ref parameter with the result
282 | * Use-Case #3. Function prints the result
283 |
284 | _Note: This is just to show how the submit function works. Options are not exclusive_
285 |
286 | ## Use-Case #1
287 | The multiply function with a return looks like this:
288 |
289 | ```c
290 | // Simple function that adds multiplies two numbers and returns the result
291 | int multiply(const int a, const int b) {
292 | const int res = a * b;
293 | return res;
294 | }
295 | ```
296 |
297 | Then, the submit:
298 |
299 | ```c
300 | // The type of future is given by the return type of the function
301 | std::future future = pool.submit(multiply, 2, 3);
302 | ```
303 |
304 | We can also use the **auto** keyword for convenience:
305 |
306 | ```c
307 | auto future = pool.submit(multiply, 2, 3);
308 | ```
309 |
310 | Nice, when the work is finished by the thread pool we know that the future will get updated and we can retrieve the result calling:
311 | ```c
312 | const int result = future.get();
313 | std::cout << result << std::endl;
314 | ```
315 |
316 | The get() function of std::future always return the type T of the future. **This type will always be equal to the return type of the function passed to the submit method**. In this case, int.
317 |
318 | ## Use-Case #2
319 | The multiply function has a parameter passed by ref:
320 |
321 | ```c
322 | // Simple function that adds multiplies two numbers and updates the out_res variable passed by ref
323 | void multiply(int& out_res, const int a, const int b) {
324 | out_res = a * b;
325 | }
326 | ```
327 |
328 | Now, we have to call the submit function with a subtle difference. Because we are using templates and type deduction (universal references), the parameter passed by ref needs to be called using **std::ref(param)** to make sure that we are passing it by ref and not by value.
329 |
330 | ```c
331 | int result = 0;
332 | auto future = pool.submit(multiply, std::ref(result), 2, 3);
333 | // result is 0
334 | future.get();
335 | // result is 6
336 | std::cout << result << std::endl;
337 | ```
338 |
339 | In this case, what's the type of future? Well, as I said before, the return type will always be equal to the return type of the function passed to the submit method. Because this function is of type void, the future is **std::future**. Calling future.get() returns void. That's not very useful, but we still need to call .get() to make sure that the work has been done.
340 |
341 | ## Use-Case #3
342 | The last case is the easiest one. Our multiply function simply prints the result:
343 |
344 | We have a simple function without output parameters. For this example I implemented the following multiplication function:
345 |
346 | ```c
347 | // Simple function that adds multiplies two numbers and prints the result
348 | void multiply(const int a, const int b) {
349 | const int result = a * b;
350 | std::cout << result << std::endl;
351 | }
352 | ```
353 |
354 | Then, we can simply call:
355 |
356 | ```c
357 | auto future = pool.submit(multiply, 2, 3);
358 | future.get();
359 | ```
360 |
361 | In this case, we know that as soon as the multiplication is done it will be printed. If we care when this is done, we can wait for it calling future.get().
362 |
363 | Checkout the [main](https://github.com/mtrebi/thread-pool/blob/master/src/main.cpp) program for a complete example.
364 |
365 | # Future work
366 |
367 | * Make it more reliable and safer (exceptions)
368 | * Find a better way to use it with member functions (thanks to @rajenk)
369 | * Run benchmarks and improve performance if needed
370 | * Evaluate performance and impact of std::function in the heap and try alternatives if necessary. (thanks to @JensMunkHansen)
371 |
372 | # References
373 |
374 | * [MULTI-THREADED PROGRAMMING TERMINOLOGY - 2017](http://www.bogotobogo.com/cplusplus/multithreaded.php): Fast analysis of how a multi-thread system works
375 |
376 | * [Universal References in C++11—Scott Meyers](https://isocpp.org/blog/2012/11/universal-references-in-c11-scott-meyers): Universal references in C++11 by Scott Meyers
377 |
378 | * [Perfect forwarding and universal references in C++](http://eli.thegreenplace.net/2014/perfect-forwarding-and-universal-references-in-c/): Article about how and when to use perfect forwarding and universal references
379 |
380 | * [C++ documentation](http://www.cplusplus.com/reference/): Thread, conditional variables, mutex and many others...
381 |
--------------------------------------------------------------------------------
/affinity.patch:
--------------------------------------------------------------------------------
1 | --- ThreadPool.h Wed May 17 15:01:04 2017
2 | +++ ThreadPool.h Sun Mar 4 04:32:07 2018
3 | @@ -1,5 +1,18 @@
4 | #pragma once
5 |
6 | +#ifdef AFFINITY
7 | +#if defined __sun__
8 | +#include
9 | +#include
10 | +#include
11 | +#include /* For sysconf */
12 | +#elif __linux__
13 | +#include /* For fprintf */
14 | +#include
15 | +#endif
16 | +#endif
17 | +
18 | +#include /* For std::size_t */
19 | #include
20 | #include
21 | #include
22 | @@ -14,10 +27,10 @@
23 | private:
24 | class ThreadWorker {
25 | private:
26 | - int m_id;
27 | + std::size_t m_id;
28 | ThreadPool * m_pool;
29 | public:
30 | - ThreadWorker(ThreadPool * pool, const int id)
31 | + ThreadWorker(ThreadPool * pool, const std::size_t id)
32 | : m_pool(pool), m_id(id) {
33 | }
34 |
35 | @@ -45,7 +58,7 @@
36 | std::mutex m_conditional_mutex;
37 | std::condition_variable m_conditional_lock;
38 | public:
39 | - ThreadPool(const int n_threads)
40 | + ThreadPool(const std::size_t n_threads)
41 | : m_threads(std::vector(n_threads)), m_shutdown(false) {
42 | }
43 |
44 | @@ -57,7 +70,44 @@
45 |
46 | // Inits thread pool
47 | void init() {
48 | - for (int i = 0; i < m_threads.size(); ++i) {
49 | + #if (defined __sun__ || defined __linux__) && defined AFFINITY
50 | + std::size_t v_cpu = 0;
51 | + std::size_t v_cpu_max = std::thread::hardware_concurrency() - 1;
52 | + #endif
53 | +
54 | + #if defined __sun__ && defined AFFINITY
55 | + std::vector v_cpu_id; /* Struct for CPU/core ID */
56 | +
57 | + processorid_t i, cpuid_max;
58 | + cpuid_max = sysconf(_SC_CPUID_MAX);
59 | + for (i = 0; i <= cpuid_max; i++) {
60 | + if (p_online(i, P_STATUS) != -1) /* Get only online cores ID */
61 | + v_cpu_id.push_back(i);
62 | + }
63 | + #endif
64 | +
65 | + for (std::size_t i = 0; i < m_threads.size(); ++i) {
66 | +
67 | + #if (defined __sun__ || defined __linux__) && defined AFFINITY
68 | + if (v_cpu > v_cpu_max) {
69 | + v_cpu = 0;
70 | + }
71 | +
72 | + #ifdef __sun__
73 | + processor_bind(P_LWPID, P_MYID, v_cpu_id[v_cpu], NULL);
74 | + #elif __linux__
75 | + cpu_set_t mask;
76 | + CPU_ZERO(&mask);
77 | + CPU_SET(v_cpu, &mask);
78 | + pthread_t thread = pthread_self();
79 | + if (pthread_setaffinity_np(thread, sizeof(cpu_set_t), &mask) != 0) {
80 | + fprintf(stderr, "Error setting thread affinity\n");
81 | + }
82 | + #endif
83 | +
84 | + ++v_cpu;
85 | + #endif
86 | +
87 | m_threads[i] = std::thread(ThreadWorker(this, i));
88 | }
89 | }
90 | --- SafeQueue.h Wed May 17 15:01:04 2017
91 | +++ SafeQueue.h Sun Mar 4 04:32:07 2018
92 | @@ -28,7 +28,7 @@
93 | return m_queue.empty();
94 | }
95 |
96 | - int size() {
97 | + std::size_t size() {
98 | std::unique_lock lock(m_mutex);
99 | return m_queue.size();
100 | }
101 |
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/example/main.cpp:
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1 | #include
2 | #include
3 |
4 | #include "../include/ThreadPool.h"
5 |
6 | std::random_device rd;
7 | std::mt19937 mt(rd());
8 | std::uniform_int_distribution dist(-1000, 1000);
9 | auto rnd = std::bind(dist, mt);
10 |
11 |
12 | void simulate_hard_computation() {
13 | std::this_thread::sleep_for(std::chrono::milliseconds(2000 + rnd()));
14 | }
15 |
16 | // Simple function that adds multiplies two numbers and prints the result
17 | void multiply(const int a, const int b) {
18 | simulate_hard_computation();
19 | const int res = a * b;
20 | std::cout << a << " * " << b << " = " << res << std::endl;
21 | }
22 |
23 | // Same as before but now we have an output parameter
24 | void multiply_output(int & out, const int a, const int b) {
25 | simulate_hard_computation();
26 | out = a * b;
27 | std::cout << a << " * " << b << " = " << out << std::endl;
28 | }
29 |
30 | // Same as before but now we have an output parameter
31 | int multiply_return(const int a, const int b) {
32 | simulate_hard_computation();
33 | const int res = a * b;
34 | std::cout << a << " * " << b << " = " << res << std::endl;
35 | return res;
36 | }
37 |
38 |
39 | int main(int argc, char *argv[])
40 | {
41 | // Create pool with 3 threads
42 | ThreadPool pool(3);
43 |
44 | // Initialize pool
45 | pool.init();
46 |
47 | // Submit (partial) multiplication table
48 | for (int i = 1; i < 3; ++i) {
49 | for (int j = 1; j < 10; ++j) {
50 | pool.submit(multiply, i, j);
51 | }
52 | }
53 |
54 | // Submit function with output parameter passed by ref
55 | int output_ref;
56 | auto future1 = pool.submit(multiply_output, std::ref(output_ref), 5, 6);
57 |
58 | // Wait for multiplication output to finish
59 | future1.get();
60 | std::cout << "Last operation result is equals to " << output_ref << std::endl;
61 |
62 | // Submit function with return parameter
63 | auto future2 = pool.submit(multiply_return, 5, 3);
64 |
65 | // Wait for multiplication output to finish
66 | int res = future2.get();
67 | std::cout << "Last operation result is equals to " << res << std::endl;
68 |
69 | pool.shutdown();
70 |
71 | return 0;
72 | }
73 |
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/include/SafeQueue.h:
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1 | #pragma once
2 |
3 | #include
4 | #include
5 |
6 | // Thread safe implementation of a Queue using an std::queue
7 | template
8 | class SafeQueue {
9 | private:
10 | std::queue m_queue;
11 | std::mutex m_mutex;
12 | public:
13 | SafeQueue() {
14 |
15 | }
16 |
17 | SafeQueue(SafeQueue& other) {
18 | //TODO:
19 | }
20 |
21 | ~SafeQueue() {
22 |
23 | }
24 |
25 |
26 | bool empty() {
27 | std::unique_lock lock(m_mutex);
28 | return m_queue.empty();
29 | }
30 |
31 | int size() {
32 | std::unique_lock lock(m_mutex);
33 | return m_queue.size();
34 | }
35 |
36 | void enqueue(T& t) {
37 | std::unique_lock lock(m_mutex);
38 | m_queue.push(t);
39 | }
40 |
41 | bool dequeue(T& t) {
42 | std::unique_lock lock(m_mutex);
43 |
44 | if (m_queue.empty()) {
45 | return false;
46 | }
47 | t = std::move(m_queue.front());
48 |
49 | m_queue.pop();
50 | return true;
51 | }
52 | };
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/include/ThreadPool.h:
--------------------------------------------------------------------------------
1 | #pragma once
2 |
3 | #include
4 | #include
5 | #include
6 | #include
7 | #include
8 | #include
9 | #include
10 |
11 | #include "SafeQueue.h"
12 |
13 | class ThreadPool {
14 | private:
15 | class ThreadWorker {
16 | private:
17 | int m_id;
18 | ThreadPool * m_pool;
19 | public:
20 | ThreadWorker(ThreadPool * pool, const int id)
21 | : m_pool(pool), m_id(id) {
22 | }
23 |
24 | void operator()() {
25 | std::function func;
26 | bool dequeued;
27 | while (!m_pool->m_shutdown) {
28 | {
29 | std::unique_lock lock(m_pool->m_conditional_mutex);
30 | if (m_pool->m_queue.empty()) {
31 | m_pool->m_conditional_lock.wait(lock);
32 | }
33 | dequeued = m_pool->m_queue.dequeue(func);
34 | }
35 | if (dequeued) {
36 | func();
37 | }
38 | }
39 | }
40 | };
41 |
42 | bool m_shutdown;
43 | SafeQueue> m_queue;
44 | std::vector m_threads;
45 | std::mutex m_conditional_mutex;
46 | std::condition_variable m_conditional_lock;
47 | public:
48 | ThreadPool(const int n_threads)
49 | : m_threads(std::vector(n_threads)), m_shutdown(false) {
50 | }
51 |
52 | ThreadPool(const ThreadPool &) = delete;
53 | ThreadPool(ThreadPool &&) = delete;
54 |
55 | ThreadPool & operator=(const ThreadPool &) = delete;
56 | ThreadPool & operator=(ThreadPool &&) = delete;
57 |
58 | // Inits thread pool
59 | void init() {
60 | for (int i = 0; i < m_threads.size(); ++i) {
61 | m_threads[i] = std::thread(ThreadWorker(this, i));
62 | }
63 | }
64 |
65 | // Waits until threads finish their current task and shutdowns the pool
66 | void shutdown() {
67 | m_shutdown = true;
68 | m_conditional_lock.notify_all();
69 |
70 | for (int i = 0; i < m_threads.size(); ++i) {
71 | if(m_threads[i].joinable()) {
72 | m_threads[i].join();
73 | }
74 | }
75 | }
76 |
77 | // Submit a function to be executed asynchronously by the pool
78 | template
79 | auto submit(F&& f, Args&&... args) -> std::future {
80 | // Create a function with bounded parameters ready to execute
81 | std::function func = std::bind(std::forward(f), std::forward(args)...);
82 | // Encapsulate it into a shared ptr in order to be able to copy construct / assign
83 | auto task_ptr = std::make_shared>(func);
84 |
85 | // Wrap packaged task into void function
86 | std::function wrapper_func = [task_ptr]() {
87 | (*task_ptr)();
88 | };
89 |
90 | // Enqueue generic wrapper function
91 | m_queue.enqueue(wrapper_func);
92 |
93 | // Wake up one thread if its waiting
94 | m_conditional_lock.notify_one();
95 |
96 | // Return future from promise
97 | return task_ptr->get_future();
98 | }
99 | };
100 |
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