如何传递函数参数到boost :: thread_groups :: create_thread（） [英] How to pass function parameters to boost::thread_groups::create_thread()

问题描述

我是新的 Boost.Threads ，我想了解如何传递函数参数到 boost :: thread_groups :: create_thread（）功能。阅读一些教程和增强文档后，我明白，可以简单地传递参数到这个函数，但我不能让这个方法工作。

I am new to Boost.Threads and am trying to understand how to pass function arguments to the boost::thread_groups::create_thread() function. After reading some tutorials and the boost documentations, I understand that it is possible to simply pass the arguments to this function but I can't get this method to work.

我读的另一个方法是使用函子将参数绑定到我的函数，但是会创建参数的副本，我严格要求const引用传递参数将是大矩阵（这我计划通过使用 boost :: cref（Matrix）一旦我得到这个简单的例子工作）。

The other method I read about is to use functors to bind the parameters to my function but that would create copies of the arguments and I strictly require that const references be passed since the arguments will be big matrices(this I plan to do by using boost::cref(Matrix) once I get this simple example to work).

现在，让我们来看下面的代码：

Now, let's get down to the code:

void printPower(float b, float e)
{
    cout<<b<<"\t"<<e<<"\t"<<pow(b,e)<<endl;
    boost::this_thread::yield();
    return;
}

void thr_main()
{
    boost::progress_timer timer;
    boost::thread_group threads;
    for (float e=0.; e<20.; e++)
    {
        float b=2.;
        threads.create_thread(&printPower,b,e);
    }
    threads.join_all();
    cout << "Threads Done" << endl;
}

这不会编译出以下错误：

This doesn't compile with the following error:

mt.cc: In function âvoid thr_main()â:
mt.cc:46: error: no matching function for call to âboost::thread_group::create_thread(void (*)(float, float), float&, float&)â
/usr/local/boost_1_44_0/include/boost/thread/detail/thread.hpp: In member function âvoid boost::detail::thread_data<F>::run() [with F = void (*)(float, float)]â:
mt.cc:55:   instantiated from here
/usr/local/boost_1_44_0/include/boost/thread/detail/thread.hpp:61: error: too few arguments to function

我做错了什么？

推荐答案

您不能将参数传递给 boost :: thread_group :: create_thread（）函数，因为它只有一个参数。您可以使用 boost :: bind ：

You can't pass arguments to boost::thread_group::create_thread() function, since it gets only one argument. You could use boost::bind:

threads.create_thread(boost::bind(printPower, boost::cref(b), boost::cref(e)));
#                                             ^ to avoid copying, as you wanted

要使用 boost :: bind ，可以使用 boost :: thread_group :: add_thread（） p>

Or, if you don't want to use boost::bind, you could use boost::thread_group::add_thread() like this:

threads.add_thread(new boost::thread(printPower, b, e));

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