examples/algo/phonebills_genlog.cpp

This example code is explain in A Billing System for Phone Calls (stxxl::vector and stxxl::sort)

/***************************************************************************
 * examples/algo/phonebills_genlog.cpp
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2004 Roman Dementiev <[email protected]>
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

#include <stxxl.h>

#include <fstream>
#include <ctime>

struct LogEntry
{
 long long unsigned from; // callers number
 long long unsigned to; // destination number
 time_t timestamp; // time of event
 int event; // event type 1 - call started
 // 2 - call ended
};

struct cmp
{
 bool operator () (const LogEntry& a, const LogEntry& b) const
 {
 return a.timestamp < b.timestamp;
 }
 static LogEntry min_value()
 {
 LogEntry e;
 e.timestamp = std::numeric_limits<time_t>::min();
 return e;
 }
 static LogEntry max_value()
 {
 LogEntry e;
 e.timestamp = std::numeric_limits<time_t>::max();
 return e;
 }
};

typedef stxxl::VECTOR_GENERATOR<LogEntry, 1, 1>::result vector_type;

std::ostream& operator << (std::ostream& i, const LogEntry& entry)
{
 i << entry.from << " ";
 i << entry.to << " ";
 i << entry.timestamp << " ";
 i << entry.event << "\n";
 return i;
}

int main(int argc, char* argv[])
{
 if (argc < 5)
 {
 STXXL_MSG("Usage: " << argv[0] << " ncalls avcalls main logfile");
 STXXL_MSG(" ncalls - number of calls");
 STXXL_MSG(" avcalls - average number of calls per client");
 STXXL_MSG(" main - memory to use (in MiB)");
 STXXL_MSG(" logfile - file name of the output");

 return 0;
 }
 stxxl::internal_size_type M = atol(argv[3]) * 1024 * 1024;
 const stxxl::uint64 ncalls = stxxl::atouint64(argv[1]);
 const long av_calls = atol(argv[2]);
 const stxxl::uint64 nclients = ncalls / av_calls;
 stxxl::uint64 calls_made = 0;

 time_t now = time(NULL);

 vector_type log;
 log.reserve(2 * ncalls);

 stxxl::random_number64 rnd;

 for (stxxl::uint64 number = 0;
 number < nclients && calls_made < ncalls;
 ++number)
 {
 long long int serv = std::min<long long int>(rnd(av_calls * 2), (ncalls - calls_made));
 LogEntry e;
 e.from = number;

 time_t cur = now;

 while (serv-- > 0)
 {
 cur += (time_t)(1 + rnd(3600 * 24));

 e.to = rnd(nclients);
 e.timestamp = cur;

 ++calls_made;
 e.event = 1;
 log.push_back(e);

 cur += (time_t)(1 + rnd(1800));
 e.timestamp = cur;
 e.event = 2;

 log.push_back(e);
 }
 }

 // sort events in order of their appereance
 stxxl::sort(log.begin(), log.end(), cmp(), M);

 std::fstream out(argv[4], std::ios::out);

 std::copy(log.begin(), log.end(), std::ostream_iterator<LogEntry>(out));

 STXXL_MSG("\n" << calls_made << " calls made.");
 STXXL_MSG("The log is written to '" << argv[4] << "'.");

 return 0;
}