使用boost累加器库的正确选项是什么？

Question

我正在尝试编译this example

但这一个头是不够的，我已经花了半个小时试图消除所有的错误。为什么没有指定必需的includes？

我这样做了：

#include <boost/accumulators/statistics/weighted_p_square_cumulative_distribution.hpp>
#include <vector>
#include <boost/accumulators/accumulators.hpp> 
#include <boost/test/test_tools.hpp>
#include <boost/random/lagged_fibonacci.hpp>
#include <boost/random/normal_distribution.hpp>
#include <boost/random/variate_generator.hpp>
#include <boost/range/iterator_range.hpp>
#include <boost/fusion/support/void.hpp>
#include <boost/accumulators/framework/depends_on.hpp>

using namespace boost::accumulators;
using namespace boost;

int main() {
    // tolerance in %
    double epsilon = 4;

    typedef accumulator_set<double, stats<tag::weighted_p_square_cumulative_distribution>, double > accumulator_t;

    accumulator_t acc_upper(tag::weighted_p_square_cumulative_distribution::num_cells = 100);
    accumulator_t acc_lower(tag::weighted_p_square_cumulative_distribution::num_cells = 100);

    // two random number generators
    double mu_upper = 1.0;
    double mu_lower = -1.0;
    boost::lagged_fibonacci607 rng;
    boost::normal_distribution<> mean_sigma_upper(mu_upper,1);
    boost::normal_distribution<> mean_sigma_lower(mu_lower,1);
    boost::variate_generator<boost::lagged_fibonacci607&, boost::normal_distribution<> > normal_upper(rng, mean_sigma_upper);
    boost::variate_generator<boost::lagged_fibonacci607&, boost::normal_distribution<> > normal_lower(rng, mean_sigma_lower);

    for (std::size_t i=0; i<100000; ++i)
    {
        double sample = normal_upper();
        acc_upper(sample, weight = std::exp(-mu_upper * (sample - 0.5 * mu_upper)));
    }

    for (std::size_t i=0; i<100000; ++i)
    {
        double sample = normal_lower();
        acc_lower(sample, weight = std::exp(-mu_lower * (sample - 0.5 * mu_lower)));
    }

    typedef iterator_range<std::vector<std::pair<double, double> >::iterator > histogram_type;
    histogram_type histogram_upper = weighted_p_square_cumulative_distribution(acc_upper);
    histogram_type histogram_lower = weighted_p_square_cumulative_distribution(acc_lower);

    // Note that applaying importance sampling results in a region of the distribution 
    // to be estimated more accurately and another region to be estimated less accurately
    // than without importance sampling, i.e., with unweighted samples

    for (std::size_t i = 0; i < histogram_upper.size(); ++i)
    {
        // problem with small results: epsilon is relative (in percent), not absolute!

        // check upper region of distribution
        if ( histogram_upper[i].second > 0.1 )    
            BOOST_CHECK_CLOSE( 0.5 * (1.0 + erf( histogram_upper[i].first / sqrt(2.0) )), histogram_upper[i].second, epsilon );
        // check lower region of distribution
        if ( histogram_lower[i].second < -0.1 )    
            BOOST_CHECK_CLOSE( 0.5 * (1.0 + erf( histogram_lower[i].first / sqrt(2.0) )), histogram_lower[i].second, epsilon );
    }
}

我得到了这些错误：

In file included from /opt/local/include/boost/accumulators/statistics/weighted_p_square_cumulative_distribution.hpp:17,
                 from a.cc:1:
/opt/local/include/boost/accumulators/framework/extractor.hpp: In instantiation of 'boost::accumulators::detail::accumulator_set_result<boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::weighted_p_square_cumulative_distribution, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, double>, boost::accumulators::tag::weighted_p_square_cumulative_distribution>':
/opt/local/include/boost/mpl/eval_if.hpp:38:   instantiated from 'boost::mpl::eval_if<boost::accumulators::detail::is_accumulator_set<boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::weighted_p_square_cumulative_distribution, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, double> >, boost::accumulators::detail::accumulator_set_result<boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::weighted_p_square_cumulative_distribution, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, double>, boost::accumulators::tag::weighted_p_square_cumulative_distribution>, boost::accumulators::detail::argument_pack_result<boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::weighted_p_square_cumulative_distribution, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, double>, boost::accumulators::tag::weighted_p_square_cumulative_distribution> >'
/opt/local/include/boost/accumulators/framework/extractor.hpp:57:   instantiated from 'boost::accumulators::detail::extractor_result<boost::accumulators::accumulator_set<double, boost::accumulators::stats<boost::accumulators::tag::weighted_p_square_cumulative_distribution, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, double>, boost::accumulators::tag::weighted_p_square_cumulative_distribution>'
a.cc:47:   instantiated from here
/opt/local/include/boost/accumulators/framework/extractor.hpp:36: error: no type named 'result_type' in 'struct boost::fusion::void_'
a.cc: In function 'int main()':
a.cc:47: error: no match for call to '(const boost::accumulators::extractor<boost::accumulators::tag::weighted_p_square_cumulative_distribution>) (main()::accumulator_t&)'
a.cc:48: error: no match for call to '(const boost::accumulators::extractor<boost::accumulators::tag::weighted_p_square_cumulative_distribution>) (main()::accumulator_t&)'

Answer 1

文档中显示的示例是从库的单元测试中提取出来的。看一看libs/accumulators/test/weighted_p_square_cum_dist.cpp

Answer 2

不幸的是，您没有显示您得到的编译错误，所以我将尝试在黑暗中拍摄：

你有没有使用

using namespace boost::accumulators;

在你的代码中？为了简洁起见，大多数示例都需要这样做。

编辑：

现在您发布了您的代码(我也检查了链接中的代码示例)，在我看来，这个示例是错误的。关键错误似乎是：

结构错误：“

boost：：fusion：：void_”中没有名为“result_type”的类型

但由于我没有使用boost：：累加器的经验，我不得不放弃这里:-(

也许你可以联系boost::accumulators的作者，让他知道这个例子没有开箱即用编译。他应该能够修复这个例子。你甚至可能会因为发现了问题而获得赞誉:-)

Answer 3

 error: no type named ‘result_type’ in ‘struct boost::fusion::void_’

很抱歉，我不能提供一个明确的解决方案，但我希望我能帮助找出问题所在。Boost fusion使您能够构建与结构等效的对象，其中可以使用模板参数访问字段。我为什么要告诉你这些？因为您得到的错误通常是在尝试访问一个不存在于fusion-struct中的字段时得到的错误。

这些错误是由以下几行生成的：

accumulator_t acc_upper(tag::weighted_p_square_cumulative_distribution::num_cells = 100);
accumulator_t acc_lower(tag::weighted_p_square_cumulative_distribution::num_cells = 100);

我非常确定，如果删除构造函数的参数，错误就会消失

accumulator_t acc_upper;
accumulator_t acc_lower;

我不太了解boost累加器，但错误可能来自两个原因:要么是您对accumulator_set的定义不正确(您使用的"stats“和boost累加器文档中建议的"features”之间有区别吗?)，要么是您对构造函数中使用的参数的定义(不正确)。找出哪一个，你很可能已经解决了你的编译错误。