[英]passing Lambda to pthread_create?
I search all the net for answer, but I didn't find any solution. 我搜索所有网络的答案,但我没有找到任何解决方案。 Can you please help.
你能帮忙吗? My problem is I am trying to send Lambda to another function and use
Pthread
library to run the lambda across several threads. 我的问题是我正在尝试将Lambda发送到另一个函数并使用
Pthread
库来跨多个线程运行lambda。 Next is the code: 接下来是代码:
1 #include <iostream>
2 #include <stdlib.h>
3 #include <pthread.h>
4 #include <vector>
5
6 using namespace std;
7
8
9 template<class InputIt, class Function>
10 inline Function parallel_fun(InputIt first, InputIt last, Function f)
11 {
12 pthread_t threads[4];
13
14 for (int i=0; first != last; ++first) {
15
16 pthread_create(&threads[i], nullptr,f , nullptr);
17
18 i++;
19 }
20
21 for (int i=0; i<4;i++) {
22
23 pthread_join(threads[i],nullptr);
24
25
26 }
27
28
29
30
31 return f;
32 }
33
34
35 int main()
36 {
37 int z=90;
38 vector<int> a(4);
39 a[0]=1; a[1]=2;
40 parallel_fun(a.begin(), a.end(), [=](void* data) -> void*
41 {
42 cout<<"test"<<z<<endl;
43 //do something
44 });
45
46
47
48 return 0;
49 }
I compile using the following line: g++ -std=c++0x -pthread test.cpp -oa
我使用以下行进行编译:
g++ -std=c++0x -pthread test.cpp -oa
and I receive this error: 我收到此错误:
test.cpp: In function ‘Function parallel_fun(InputIt, InputIt, Function) [with InputIt = __gnu_cxx::__normal_iterator<int*, std::vector<int> >, Function = main()::<lambda(void*)>]’:
test.cpp:44:11: instantiated from here
test.cpp:16:10: error: cannot convert ‘main()::<lambda(void*)>’ to ‘void* (*)(void*)’ for argument ‘3’ to ‘int pthread_create(pthread_t*, const pthread_attr_t*, void* (*)(void*), void*)’
I am not sure about the new C++11 API.
我不确定新的C ++ 11 API。 I don't think I have enough time to learn new API.
我认为我没有足够的时间学习新的API。
This is your lucky day. 这是你的幸运日。 The C++11 API was strongly influenced by pthreads.
C ++ 11 API受到pthreads的强烈影响。 There is nearly a mechanical translation.
几乎是机械翻译。 Here is your code cast in C++11:
这是您在C ++ 11中的代码转换:
#include <iostream>
#include <stdlib.h>
#include <thread>
#include <vector>
template<class InputIt, class Function>
inline
Function
parallel_fun(InputIt first, InputIt last, Function f)
{
std::thread threads[4];
for (int i=0; first != last; ++first)
{
threads[i] = std::thread(f);
i++;
}
for (int i=0; i<4;i++)
{
threads[i].join();
}
return f;
}
int main()
{
int z=90;
std::vector<int> a(4);
a[0]=1; a[1]=2;
parallel_fun(a.begin(), a.end(), [=]()
{
std::cout<<"test" << z << std::endl;
//do something
});
}
Your alternative, is to figure out how std::thread
gets implemented on top of pthreads, which trust me, is much more complicated than the C++11 translation shown above. 你的另一种方法是弄清楚如何在pthreads之上实现
std::thread
,它相信我,比上面显示的C ++ 11转换要复杂得多。
There is no conversion from a lambda to a function pointer unless the lambda has no captures. 除非 lambda没有捕获, 否则没有从lambda到函数指针的转换。 (§5.1.2p6).
(§5.1.2p6)。 So if you require the capture of
z
, you are out of luck. 所以如果你需要捕获
z
,那你就不走运了。
The C interface expects you to use the void*
argument for your closures. C接口希望您为闭包使用
void*
参数。 You could do that, which would be ugly (but C-like), or you could use the new C++11 thread support library, if your C++ environment supports it. 您可以这样做,这将是丑陋的(但类似于C),或者您可以使用新的C ++ 11线程支持库,如果您的C ++环境支持它。
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