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

   1 // Copyright (C) 2016-2018 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 // { dg-require-cstdint "" }
  21
  22 #ifndef _GLIBCXX_ASSERTIONS
  23 // Make std::uniform_int_distribution check its parameters
  24 # define _GLIBCXX_ASSERTIONS
  25 #endif
  26
  27 #include <algorithm>
  28 #include <random>
  29 #include <climits>
  30 #include <testsuite_hooks.h>
  31 #include <testsuite_iterators.h>
  32
  33 std::mt19937 rng;
  34
  35 using std::sample;
  36 using __gnu_test::test_container;
  37 using __gnu_test::output_iterator_wrapper;
  38
  39 void
  40 test01()
  41 {
  42   int pop[UCHAR_MAX]  = { };
  43   for (int i = SCHAR_MAX; i < UCHAR_MAX; ++i)
  44     pop[i] = 1;
  45   const signed char sample_size = SCHAR_MAX; // PR libstdc++/77994
  46   int out[sample_size] = { };
  47
  48   // random access iterators for both population and result
  49   // (uses reservoir sampling)
  50   auto it = sample(std::begin(pop), std::end(pop), out, sample_size, rng);
  51   auto sum = std::accumulate(out, it, 0);
  52   VERIFY( sum != 0 ); // exceedingly unlikely!
  53
  54   // random access iterator for population and output iterator for result
  55   // (uses selection sampling)
  56   test_container<int, output_iterator_wrapper> samp2(out);
  57   sample(std::begin(pop), std::end(pop), samp2.begin(), sample_size, rng);
  58   sum = std::accumulate(std::begin(out), std::end(out), 0);
  59   VERIFY( sum != 0 );
  60 }
  61
  62 int
  63 main()
  64 {
  65   test01();
  66 }