N Boost interval_set的组合

Question

我有一个服务,在4个不同的地方停运.我将每个位置中断建模为Boost ICL interval_set.我想知道什么时候至少有N个地点有活动中断.

因此,在这个答案之后,我实现了一个组合算法,因此我可以通过interval_set交集创建elemenets之间的组合.

当这个过程结束时,我应该有一定数量的interval_set,每个interval_set同时定义N个位置的中断,最后一步将加入它们以获得所需的全图.

问题是我正在调试代码,当打印每个交集的时间到了,输出文本变得疯狂(即使我正在逐步使用gdb进行调试),我看不到它们,导致大量CPU使用.

我想我不知何故发送输出的内存比我应该多,但我看不出问题出在哪里.

这是一个SSCCE:

#include <boost/icl/interval_set.hpp>
#include <algorithm>
#include <iostream>
#include <vector>


int main() {
    // Initializing data for test
    std::vector<boost::icl::interval_set<unsigned int> > outagesPerLocation;
    for(unsigned int j=0; j<4; j++){
        boost::icl::interval_set<unsigned int> outages;
        for(unsigned int i=0; i<5; i++){
            outages += boost::icl::discrete_interval<unsigned int>::closed(
                (i*10), ((i*10) + 5 - j));
        }
        std::cout << "[Location " << (j+1) << "] " << outages << std::endl;
        outagesPerLocation.push_back(outages);
    }

    // So now we have a vector of interval_sets, one per location. We will combine
    // them so we get an interval_set defined for those periods where at least
    // 2 locations have an outage (N)
    unsigned int simultaneusOutagesRequired = 2;  // (N)

    // Create a bool vector in order to filter permutations, and only get
    // the sorted permutations (which equals the combinations)
    std::vector<bool> auxVector(outagesPerLocation.size());
    std::fill(auxVector.begin() + simultaneusOutagesRequired, auxVector.end(), true);

    // Create a vector where combinations will be stored
    std::vector<boost::icl::interval_set<unsigned int> > combinations;

    // Get all the combinations of N elements
    unsigned int numCombinations = 0;
    do{
        bool firstElementSet = false;
        for(unsigned int i=0; i<auxVector.size(); i++){
            if(!auxVector[i]){
                if(!firstElementSet){
                    // First location, insert to combinations vector
                    combinations.push_back(outagesPerLocation[i]);
                    firstElementSet = true;
                }
                else{
                    // Intersect with the other locations
                    combinations[numCombinations] -= outagesPerLocation[i];
                }
            }
        }
        numCombinations++;
        std::cout << "[-INTERSEC-] " << combinations[numCombinations] << std::endl;  // The problem appears here
    }
    while(std::next_permutation(auxVector.begin(), auxVector.end()));

    // Get the union of the intersections and see the results
    boost::icl::interval_set<unsigned int> finalOutages;
    for(std::vector<boost::icl::interval_set<unsigned int> >::iterator
        it = combinations.begin(); it != combinations.end(); it++){
        finalOutages += *it;
    }

    std::cout << finalOutages << std::endl;
    return 0;
}

有帮助吗？

Answer 1

正如我猜测的那样,这里有一种"高级"方法.

提升ICL容器不仅仅是"美化的间隔起点/终点对"的容器.他们的目的是实现这一点相结合,搜索,在一般优化的方式经营.

所以你不必.

如果你让图书馆做它应该做的事情:

using TimePoint = unsigned;
using DownTimes = boost::icl::interval_set<TimePoint>;
using Interval  = DownTimes::interval_type;
using Records   = std::vector<DownTimes>;

使用功能域typedef会引发更高级别的方法.现在,让我们问一下假设的"商业问题":

我们对每个位置停机记录实际上想做些什么？

好吧,我们基本上想要

1. 为所有可辨别的时间段计算它们
2. 过滤那些标记至少为2的那些
3. 最后,我们想展示剩下的"合并"时段.

好的,工程师:实现它!

1. 嗯.清点.它能有多难？

   elegant优雅解决方案的关键是选择正确的数据结构

   using Tally     = unsigned; // or: bit mask representing affected locations?
   using DownMap   = boost::icl::interval_map<TimePoint, Tally>;
   

   现在它只是批量插入:

   // We will do a tally of affected locations per time slot
   DownMap tallied;
   for (auto& location : records)
       for (auto& incident : location)
           tallied.add({incident, 1u});
   

2. 好的,让我们过滤一下.我们只需要适用于我们的DownMap的谓词

   // define threshold where at least 2 locations have an outage
   auto exceeds_threshold = [](DownMap::value_type const& slot) {
       return slot.second >= 2;
   };
   

3. 合并时间段!

   其实.我们只是创建另一个DownTimes集.只是,这次不是每个地点.

   数据结构的选择再次获胜:

   // just printing the union of any criticals:
   DownTimes merged;
   for (auto&& slot : tallied | filtered(exceeds_threshold) | map_keys)
       merged.insert(slot);
   

报告!

std::cout << "Criticals: " << merged << "\n";

请注意,我们无处接近操纵数组索引,重叠或非重叠间隔,闭合或开放边界.或者,[eeeeek!]收集元素的强力排列.

我们刚刚阐述了目标,让图书馆开展工作.

完整的演示

Live On Coliru

#include <boost/icl/interval_set.hpp>
#include <boost/icl/interval_map.hpp>
#include <boost/range.hpp>
#include <boost/range/algorithm.hpp>
#include <boost/range/adaptors.hpp>
#include <boost/range/numeric.hpp>
#include <boost/range/irange.hpp>
#include <algorithm>
#include <iostream>
#include <vector>

using TimePoint = unsigned;
using DownTimes = boost::icl::interval_set<TimePoint>;
using Interval  = DownTimes::interval_type;
using Records   = std::vector<DownTimes>;

using Tally     = unsigned; // or: bit mask representing affected locations?
using DownMap   = boost::icl::interval_map<TimePoint, Tally>;

// Just for fun, removed the explicit loops from the generation too. Obviously,
// this is bit gratuitous :)
static DownTimes generate_downtime(int j) {
    return boost::accumulate(
            boost::irange(0, 5),
            DownTimes{},
            [j](DownTimes accum, int i) { return accum + Interval::closed((i*10), ((i*10) + 5 - j)); }
        );
}

int main() {
    // Initializing data for test
    using namespace boost::adaptors;
    auto const records = boost::copy_range<Records>(boost::irange(0,4) | transformed(generate_downtime));

    for (auto location : records | indexed()) {
        std::cout << "Location " << (location.index()+1) << " " << location.value() << std::endl;
    }

    // We will do a tally of affected locations per time slot
    DownMap tallied;
    for (auto& location : records)
        for (auto& incident : location)
            tallied.add({incident, 1u});

    // We will combine them so we get an interval_set defined for those periods
    // where at least 2 locations have an outage
    auto exceeds_threshold = [](DownMap::value_type const& slot) {
        return slot.second >= 2;
    };

    // just printing the union of any criticals:
    DownTimes merged;
    for (auto&& slot : tallied | filtered(exceeds_threshold) | map_keys)
        merged.insert(slot);

    std::cout << "Criticals: " << merged << "\n";
}

哪个打印

Location 1 {[0,5][10,15][20,25][30,35][40,45]}
Location 2 {[0,4][10,14][20,24][30,34][40,44]}
Location 3 {[0,3][10,13][20,23][30,33][40,43]}
Location 4 {[0,2][10,12][20,22][30,32][40,42]}
Criticals: {[0,4][10,14][20,24][30,34][40,44]}