Fast Reading

#include <iostream>
#include <fstream>
#include <algorithm>                              // for std::find
#include <iostream>                               // for std::cout
#include <cstring>
#include <vector>

#include <boost/iostreams/device/mapped_file.hpp> // for mmap
#include <boost/iostreams/stream.hpp>             // for stream
#include <boost/algorithm/string/split.hpp>       // for split operation
#include<boost/algorithm/string.hpp>              // for is_any_of

#include <chrono>

using hrclock = std::chrono::high_resolution_clock;
using namespace std;

const string file_path = "bcsstk01.txt";

int main()
{
    vector<double> vec;

    int n(48), nnz(224);
    long diffs[4];

    // Basic reading
    ifstream ifs2(file_path);
    int i, j;
    double v;
    clock_t start = clock();
    while (ifs2 >> i >> j >> v) {
        /* action */
        cout << i << "\t" << j << "\t" << v << "\n";
        vec.push_back(v);
    }
    vec.clear();
    clock_t end = clock();
    long diff = end - start;
    diffs[0] = diff;
    cout << "Basic: " << diff << endl;
    ifs2.close();

    // Getline reading
    ifstream ifs(file_path);
    std::string s;
    start = clock();
    while (getline(ifs, s)) {
        auto it = s.begin();
        if (it != s.end()) {
            string ss = string{ it, s.end() };
            /* action */
            cout << ss << "\n";
            vector<string> strVec;
            boost::algorithm::split(strVec, ss, boost::is_any_of("\t "), boost::token_compress_on);
            vec.push_back(atof(strVec[strVec.size() - 1].c_str()));
        }
    }
    vec.clear();
    end = clock();
    ifs.close();
    diff = end - start;
    diffs[1] = diff;
    cout << "Getline: " << diff << endl;

    /*
        http://stackoverflow.com/questions/26252893/read-till-end-of-a-boost-memory-mapped-file-in-vc
    */
    // Boost (Using the raw Device source)
    boost::iostreams::mapped_file mmap(file_path, boost::iostreams::mapped_file::readonly);
    auto f = mmap.const_data();
    auto l = f + mmap.size();

    uintmax_t m_numLines = 0;
    start = clock();
    int k = 0;
    while (f && f != l) {
        if ((f = static_cast<const char*>(memchr(f, '\n', l - f)))) {
            cout << f << "\n";
            vector<string> strVec;
            boost::algorithm::split(strVec, f, boost::is_any_of("\t "), boost::token_compress_on);
            vec.push_back(atof(strVec[strVec.size() - 1].c_str()));

            m_numLines++, f++;
        }
    }
    vec.clear();
    end = clock();
    diff = end - start;
    diffs[2] = diff;
    cout << "Boost2: " << diff << "\n";
    cout << "m_numLines = " << m_numLines << "\n";

    // Boost (Wrapping the source device in a istream2)
    using boost::iostreams::mapped_file_source;
    using boost::iostreams::stream;

    mapped_file_source file(file_path);
    stream<mapped_file_source> is(file, std::ios::binary);

    std::string line;

    m_numLines = 0;
    start = clock();
    while (std::getline(is, line))
    {
        cout << line << "\n";
        vector<string> strVec;
        boost::algorithm::split(strVec, line, boost::is_any_of("\t "), boost::token_compress_on);
        vec.push_back(atof(strVec[strVec.size() - 1].c_str()));

        m_numLines++;
    }
    vec.clear();
    end = clock();
    diff = end - start;
    diffs[3] = diff;
    cout << "Boost1 (istream): " << diff << "\n";
    cout << "m_numLines = " << m_numLines << "\n";

    for (int l = 0; l < 4; l++) {
        cout << l << "\t" << diffs[l] << "\n";
    }
}

// FILE
1 1 2832268.51852
5 1 1e6
6 1 2083333.33333
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11 1 1e6
19 1 -2.8e6
25 1 -28935.1851852
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