libstdc++-v3/testsuite/25_algorithms/sample/2.cc

   1 // Copyright (C) 2016-2017 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-options "-std=gnu++17" }
  19 // { dg-do run { target c++17 } }
  20
  21 #ifndef _GLIBCXX_ASSERTIONS
  22 // Make std::uniform_int_distribution check its parameters
  23 # define _GLIBCXX_ASSERTIONS
  24 #endif
  25
  26 #include <algorithm>
  27 #include <random>
  28 #include <climits>
  29 #include <testsuite_hooks.h>
  30 #include <testsuite_iterators.h>
  31
  32 std::mt19937 rng;
  33
  34 using std::sample;
  35 using __gnu_test::test_container;
  36 using __gnu_test::output_iterator_wrapper;
  37
  38 void
  39 test01()
  40 {
  41   int pop[UCHAR_MAX]  = { };
  42   for (int i = SCHAR_MAX; i < UCHAR_MAX; ++i)
  43     pop[i] = 1;
  44   const signed char sample_size = SCHAR_MAX; // PR libstdc++/77994
  45   int out[sample_size] = { };
  46
  47   // random access iterators for both population and result
  48   // (uses reservoir sampling)
  49   auto it = sample(std::begin(pop), std::end(pop), out, sample_size, rng);
  50   auto sum = std::accumulate(out, it, 0);
  51   VERIFY( sum != 0 ); // exceedingly unlikely!
  52
  53   // random access iterator for population and output iterator for result
  54   // (uses selection sampling)
  55   test_container<int, output_iterator_wrapper> samp2(out);
  56   sample(std::begin(pop), std::end(pop), samp2.begin(), sample_size, rng);
  57   sum = std::accumulate(std::begin(out), std::end(out), 0);
  58   VERIFY( sum != 0 );
  59 }
  60
  61 int
  62 main()
  63 {
  64   test01();
  65 }