forked from boostorg/algorithm
Documentation for the minmax library.
Moved from libs/minmax/ to libs/algorithm/minmax Also changed documentation to reflect use of Boost.tuple and separation into two header files. --Herve' [SVN r23308]
This commit is contained in:
Hervé Brönnimann
207
minmax/example/minmax_timer.cpp
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207
minmax/example/minmax_timer.cpp
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#include <utility>
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#include <functional>
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#include <algorithm>
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#include <numeric>
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#include <iterator>
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#include <vector>
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#include <list>
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#include <set>
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#include <iostream>
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// What's the proper BOOST_ flag for <iomanip.h> vs <ios>
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#include <iomanip>
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#include <boost/timer.hpp>
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#include <boost/algorithm/minmax.hpp>
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template <class T1, class T2>
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void tie(std::pair<T1, T2> p, T1& min, T2& max)
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{
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min = p.first; max = p.second;
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}
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template <class Value>
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struct less_count : std::less<Value> {
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less_count(less_count<Value> const& lc) : _M_counter(lc._M_counter) {}
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less_count(int& counter) : _M_counter(counter) {}
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bool operator()(Value const& a, Value const& b) const {
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++_M_counter;
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return std::less<Value>::operator()(a,b);
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}
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void reset() {
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_M_counter = 0;
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}
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private:
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int& _M_counter;
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};
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inline int opt_min_count(int n) {
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return (n==0) ? 0 : n-1;
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}
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inline int opt_minmax_count(int n) {
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if (n < 2) return 0;
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if (n == 2) return 1;
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return (n%2 == 0) ? 3*(n/2)-1 : 3*(n/2)+1;
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}
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inline int opt_boost_minmax_count(int n) {
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if (n < 2) return 0;
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if (n == 2) return 1;
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return (n%2 == 0) ? 3*(n/2)-2 : 3*(n/2);
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}
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int repeats = 10;
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#define TIMER( n, cmd , cmdname ) \
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t.restart(); \
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for (int i=0; i<repeats; ++i) { cmd ; } \
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std::cout << " " << std::setprecision(4) \
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<< (double)n*repeats/t.elapsed()/1.0E6 \
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<< "M items/sec " << cmdname << "\n"
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#define CTIMER( n, cmd , cmdname, count, opt ) \
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t.restart(); lc.reset(); \
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for (int i=0; i<repeats; ++i) { cmd ; } \
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std::cout << " " << std::setprecision(4) \
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<< (double)n*repeats/t.elapsed()/1.0E6 \
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<< "M items/sec " << cmdname \
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<< " ("<< (count)/repeats << " vs " << opt << ")\n"
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template <class CIterator>
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void test_minmax_element(CIterator first, CIterator last, int n, char* name)
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{
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typedef typename std::iterator_traits<CIterator>::value_type vtype;
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boost::timer t;
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std::cout << " ON " << name << " WITH OPERATOR<()\n";
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TIMER( n, std::min_element(first, last),
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"std::min_element" << name << "");
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TIMER( n, std::max_element(first, last),
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"std::max_element" << name << "");
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TIMER( n, boost::first_min_element(first, last),
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"boost::first_min_element" << name << "");
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TIMER( n, boost::last_min_element(first, last),
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"boost::last_min_element" << name << " ");
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TIMER( n, boost::first_max_element(first, last),
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"boost::first_max_element" << name << "");
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TIMER( n, boost::last_max_element(first, last),
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"boost::last_max_element" << name << " ");
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TIMER( n, boost::minmax_element(first, last),
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"boost::minmax_element" << name << " ");
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TIMER( n, boost::first_min_last_max_element(first, last),
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"boost::first_min_last_max_element" << name << "");
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TIMER( n, boost::last_min_first_max_element(first, last),
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"boost::last_min_first_max_element" << name << "");
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TIMER( n, boost::last_min_last_max_element(first, last),
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"boost::last_min_last_max_element" << name << " ");
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#define pred std::bind2nd( std::greater<vtype>(), vtype(10) )
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TIMER( n, boost::min_element_if(first, last, pred),
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"boost::min_element_if" << name << "");
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TIMER( n, boost::max_element_if(first, last, pred),
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"boost::max_element_if" << name << "");
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TIMER( n, std::min_element(boost::make_filter_iterator(first, last, pred),
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boost::make_filter_iterator(last, last, pred)),
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"std::min_element_with_filter_iterator" << name << "");
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TIMER( n, std::max_element(boost::make_filter_iterator(first, last, pred),
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boost::make_filter_iterator(last, last, pred)),
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"std::max_element_if_with_filter_iterator" << name << "");
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#undef pred
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int counter = 0;
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less_count<vtype> lc(counter);
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std::cout << " ON " << name << " WITH LESS<> AND COUNTING COMPARISONS\n";
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CTIMER( n, std::min_element(first, last, lc),
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"std::min_element" << name << " ",
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counter, opt_min_count(n) );
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CTIMER( n, std::max_element(first, last, lc),
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"std::max_element" << name << " ",
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counter, opt_min_count(n) );
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CTIMER( n, boost::first_min_element(first, last, lc),
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"boost::first_min_element" << name << "",
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counter, opt_min_count(n) );
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CTIMER( n, boost::last_min_element(first, last, lc),
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"boost::last_max_element" << name << " ",
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counter, opt_min_count(n) );
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CTIMER( n, boost::first_max_element(first, last, lc),
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"boost::first_min_element" << name << "",
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counter, opt_min_count(n) );
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CTIMER( n, boost::last_max_element(first, last, lc),
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"boost::last_max_element" << name << " ",
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counter, opt_min_count(n) );
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CTIMER( n, boost::minmax_element(first, last, lc),
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"boost::minmax_element" << name << " ",
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counter, opt_minmax_count(n) );
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CTIMER( n, boost::first_min_last_max_element(first, last, lc),
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"boost::first_min_last_max_element" << name << "",
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counter, opt_boost_minmax_count(n) );
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CTIMER( n, boost::last_min_first_max_element(first, last, lc),
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"boost::last_min_first_max_element" << name << "",
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counter, opt_boost_minmax_count(n) );
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CTIMER( n, boost::last_min_last_max_element(first, last, lc),
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"boost::last_min_last_max_element" << name << " ",
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counter, opt_minmax_count(n) );
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}
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template <class Container, class Iterator, class Value>
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void test_container(Iterator first, Iterator last, int n, char* name)
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{
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Container c(first, last);
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typename Container::iterator fit(c.begin()), lit(c.end());
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test_minmax_element(fit, lit, n, name);
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}
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template <class Iterator>
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void test_range(Iterator first, Iterator last, int n)
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{
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typedef typename std::iterator_traits<Iterator>::value_type Value;
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// Test various containers with these values
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test_container< std::vector<Value>, Iterator, Value >(first, last, n, "<vector>");
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#ifndef ONLY_VECTOR
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test_container< std::list<Value>, Iterator, Value >(first, last, n, "<list> ");
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test_container< std::multiset<Value>, Iterator, Value >(first, last, n, "<set> ");
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#endif
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}
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template <class Value>
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void test(int n)
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{
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// Populate test vector with identical values
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std::cout << "IDENTICAL VALUES... \n";
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std::vector<Value> test_vector(n, Value(1));
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typename std::vector<Value>::iterator first( test_vector.begin() );
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typename std::vector<Value>::iterator last( test_vector.end() );
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test_range(first, last, n);
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// Populate test vector with two values
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std::cout << "TWO DISTINCT VALUES...\n";
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typename std::vector<Value>::iterator middle( first + n/2 );
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std::fill(middle, last, Value(2));
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test_range(first, last, n);
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// Populate test vector with increasing values
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std::cout << "INCREASING VALUES... \n";
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std::fill(first, last, Value(1));
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std::accumulate(first, last, Value(0));
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test_range(first, last, n);
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// Populate test vector with decreasing values
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std::cout << "DECREASING VALUES... \n";
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std::reverse(first, last);
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test_range(first, last, n);
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// Populate test vector with random values
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std::cout << "RANDOM VALUES... \n";
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std::random_shuffle(first, last);
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test_range(first, last, n);
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}
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int
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main(char argc, char** argv)
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{
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int n = 100;
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if (argc > 1) n = atoi(argv[1]);
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if (argc > 2) repeats = atoi(argv[2]);
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test<int>(n);
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return 0;
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}
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