25.nth.element.cpp

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#include <algorithm>    // for nth_element, 
#include <cstring>      // for strlen, size_t
 
#include <rw_alg_test.h>
#include <rw_value.h>   // for UserClass
#include <rw_driver.h>  // for rw_test()
 
 
_RWSTD_NAMESPACE (std) { 
 
#ifndef _RWSTD_NO_EXPLICIT_INSTANTIATION
 
template
void
nth_element (RandomAccessIter<lt_comp<assign<base<cpy_ctor> > > >, 
             RandomAccessIter<lt_comp<assign<base<cpy_ctor> > > >,
             RandomAccessIter<lt_comp<assign<base<cpy_ctor> > > >);
 
template
void 
nth_element (RandomAccessIter<lt_comp<assign<base<cpy_ctor> > > >, 
             RandomAccessIter<lt_comp<assign<base<cpy_ctor> > > >,
             RandomAccessIter<lt_comp<assign<base<cpy_ctor> > > >,
             binary_predicate<lt_comp<assign<base<cpy_ctor> > > >);
 
#endif // _RWSTD_NO_EXPLICIT_INSTANTIATION
 
}   // namespace std
 
 
template <class T>
struct StrictWeakLess 
{
    static std::size_t funcalls_;
 
    // dummy arguments provided to prevent the class from being
    // default constructible and implicit conversion from int
    StrictWeakLess (int /* dummy */, int /* dummy */) {
        funcalls_ = 0;
    }
 
    // return a type other than bool but one that is implicitly
    // convertible to bool to detect incorrect assumptions
    conv_to_bool operator() (const T &x, const T &y) /* non-const */ {
        ++funcalls_;
        return conv_to_bool::make (x.data_.val_ < y.data_.val_);
    }
 
    static const char* name () { return "StrictWeakLess"; }
 
private:
    void operator= (StrictWeakLess&);   // not assignable
};
 
template<class T>
std::size_t StrictWeakLess<T>::funcalls_;
 
 
// exrcises nth_element
template <class T, class Predicate>
void test_nth_element (int                 line,
                       const char         *src,
                       const std::size_t   N,
                       const std::size_t   nth,
                       const T*,
                       const Predicate    *ppred)
{
    _RWSTD_UNUSED (ppred);
 
    typedef RandomAccessIter<T> RandIter;
 
    const RandIter it(0, 0, 0);
 
    const char* const itname = type_name (it, (T*)0);
    const char* const fname = "nth_element";
    const char* const funname = Predicate::name();
 
    const std::size_t nsrc = src ? std::strlen (src) : N;
 
    T::gen_ = gen_rnd;
    T* const xsrc = src ? T::from_char (src, nsrc) : new T[nsrc];
 
    T* const xsrc_end = xsrc + nsrc;
 
    //                                 current,    first, last
    const RandIter first  = make_iter (xsrc,       xsrc,  xsrc_end, it);
    const RandIter nth_it = make_iter (xsrc + nth, xsrc,  xsrc_end, it);
    const RandIter last   = make_iter (xsrc_end,   xsrc,  xsrc_end, it);
 
    Predicate pred (0, 0);
 
    const std::size_t last_n_op_lt = T::n_total_op_lt_; 
 
    if (ppred)
        std::nth_element (first, nth_it, last, pred);
    else
        std::nth_element (first, nth_it, last);
 
    // check the results, 25.3.2, p1
    bool success = true;
    std::size_t i = 0;
    std::size_t j = 0;
 
    for (i = 0; i < nth; i++) {
        for (j = nth; j < nsrc; j++) {
            success = xsrc[i].data_.val_ <= xsrc[j].data_.val_;
            if (!success)
                break;
        }
 
        if (!success)
            break;
    }
 
    // to avoid errors in --trace mode
    i = i < nth ? i : nth - 1;
    j = j < nsrc ? j : nsrc - 1;
 
    if (src) {
        rw_assert (success, 0, line,
                   "line %d: %s<%s%{?}, %s%{;}>(\"%s\", %zu, ...) ==> "
                   "\"%{X=*.*}\", got %#c at %zu !< %#c at %zu",
                   __LINE__, fname, itname, ppred, funname, src, nth, 
                   int (sizeof (*xsrc)), int (nsrc), -1, xsrc,
                   xsrc[i].data_.val_, i, xsrc[j].data_.val_, j);
    }
    else {
        rw_assert (success, 0, line,
                   "line %d: %s<%s%{?}, %s%{;}>(%zu, %zu, ...) "
                   "got %d at %zu !< %d at %zu",
                   __LINE__, fname, itname, ppred, funname, N, nth, 
                   xsrc[i].data_.val_, i, xsrc[j].data_.val_, j);
    }
 
    // check the complexity, 25.3.2, p2
    // it should be linear, i.e. <= K * N, there K << N
    // after tests on random sequences use K == 8 as upper bound
    std::size_t n_ops = 
        ppred ? Predicate::funcalls_ : T::n_total_op_lt_ - last_n_op_lt;
    std::size_t exp_ops = 8 * nsrc;
 
    success = n_ops <= exp_ops;
 
    rw_assert (success, 0, line,
               "line %d: %s<%s%{?}, %s%{;}>(%{?}\"%s\"%{;}%{?}%zu%{;}, "
               "%zu, ...): complexity: got %zu, expected no more than %zu",
               __LINE__, fname, itname, ppred, funname, 
               src, src, !src, N, nth, n_ops, exp_ops);
 
    delete[] xsrc;
}
 
 
/* extern */ int rw_opt_nloops = 256;            // --nloops=#
/* extern */ int rw_opt_no_predicate;            // --no-predicate
/* extern */ int rw_opt_no_complexity;           // --no-complexity
 
 
template <class T, class Predicate>
void test_nth_element (const T*,
                       const Predicate *ppred)
{
    typedef RandomAccessIter<T> RandIter;
 
    const char* const itname  = type_name (RandIter (0, 0, 0), (T*)0);
    const char* const fname   = "nth_element";
    const char* const funname = Predicate::name();
 
    rw_info (0, 0, 0,
             "std::%s (%s, %2$s, %2$s%{?}, %s%{;})",
             fname, itname, ppred, funname);
 
#define TEST(src, nth)                                                  \
    test_nth_element (__LINE__, src, 0, nth, (T*)0, ppred)
 
    TEST ("a", 0);
    TEST ("aa", 1);
    TEST ("ab", 0);
 
    TEST ("jihgfedcba", 0);
    TEST ("jihgfedcba", 1);
    TEST ("jihgfedcba", 2);
    TEST ("jihgfedcba", 3);
    TEST ("jihgfedcba", 4);
    TEST ("jihgfedcba", 5);
    TEST ("jihgfedcba", 6);
    TEST ("jihgfedcba", 7);
    TEST ("jihgfedcba", 8);
    TEST ("jihgfedcba", 9);
 
    TEST ("abcdefghij", 0);
    TEST ("abcdefghij", 1);
    TEST ("abcdefghij", 2);
    TEST ("abcdefghij", 3);
    TEST ("abcdefghij", 4);
    TEST ("abcdefghij", 5);
    TEST ("abcdefghij", 6);
    TEST ("abcdefghij", 7);
    TEST ("abcdefghij", 8);
    TEST ("abcdefghij", 9);
 
    TEST ("jijgfgdcda", 5);
    TEST ("jihifefcbc", 5);
    TEST ("jiigffdcca", 5);
    TEST ("jihhfeecbb", 5);
 
    TEST ("cbbbbbbbba", 5);
    TEST ("ccbbbbbbaa", 5);
 
    TEST ("abadedghgj", 5);
    TEST ("abcbefehih", 5);
    TEST ("abbdeeghhj", 5);
    TEST ("abcceffhii", 5);
 
    TEST ("abbbbbbbbc", 5);
    TEST ("aabbbbbbcc", 5);
 
#undef TEST
 
    if (rw_opt_no_complexity) {
        rw_note (0, 0, 0,
                 "std::%s (%s, %2$s, %2$s%{?}, %s%{;}): "
                 "complexity test disabled",
                 fname, itname, ppred, funname);
    }
    else {
        rw_info (0, 0, 0,
                 "std::%s (%s, %2$s, %2$s%{?}, %s%{;}): complexity test",
                 fname, itname, ppred, funname);
 
        const std::size_t N = std::size_t (rw_opt_nloops);
        for (std::size_t i = 1; i < N; i++)
            test_nth_element (__LINE__, 0, i, i / 2, (T*)0, ppred);
    }
}
 
 
static int run_test (int, char*[])
{
    rw_info (0, 0, 0,
             "template <class %s> "
             "void std::nth_element (%1$s, %1$s, %1$s)",
             "RandomAccessIterator");
 
    test_nth_element ((UserClass*)0, (StrictWeakLess<UserClass>*)0);
 
    if (rw_opt_no_predicate) {
        rw_note (0, __FILE__, __LINE__, 
                 "std::nth_element predicate test disabled");
    }
    else {
        rw_info (0, 0, 0,
                 "template <class %s, class %s> "
                 "void std::nth_element (%1$s, %1$s, %1$s, %2$s)",
                 "RandomAccessIterator", "StrictWeakLess");
 
        const StrictWeakLess<UserClass> pred(0, 0);
        test_nth_element ((UserClass*)0, &pred);
    }
 
    return 0;
}
 
 
 
int main (int argc, char *argv[])
{
    return rw_test (argc, argv, __FILE__,
                    "lib.alg.nth_element",
                    0 /* no comment */,
                    run_test,
                    "|-nloops#0 "   // must be non-negative
                    "|-no-predicate#"
                    "|-no-complexity",
                    &rw_opt_nloops,
                    &rw_opt_no_predicate,
                    &rw_opt_no_complexity);
}