libstdc++: Add performance test for <random>

This tests std::uniform_int_distribution with various parameters and
engines.

libstdc++-v3/ChangeLog:

	* testsuite/performance/26_numerics/random_dist.cc: New test.

1 files changed, 102 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/performance/26_numerics/random_dist.cc b/libstdc++-v3/testsuite/performance/26_numerics/random_dist.cc
new file mode 100644
index 00000000000..673992d1949
--- /dev/null
+++ b/libstdc++-v3/testsuite/performance/26_numerics/random_dist.cc
@@ -0,0 +1,102 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+
+#include <random>
+#include <testsuite_performance.h>
+
+namespace counters
+{
+  __gnu_test::time_counter time;
+  __gnu_test::resource_counter resource;
+}
+
+
+template<typename Dist, typename Engine>
+void do_fill_with_uniform_ints(std::string name, Dist& d, Engine& e)
+{
+  using counters::time;
+  using counters::resource;
+
+  std::vector<typename Dist::result_type> r;
+  int n = 10000000;
+  {
+    const auto suffix = "-e" + std::to_string((int)std::log10(n));
+    r.resize(n);
+
+    start_counters(time, resource);
+    for (auto& x : r)
+      x = d(e);
+    stop_counters(time, resource);
+    report_performance(__FILE__, name+suffix, time, resource);
+    clear_counters(time, resource);
+
+    d.reset();
+
+    start_counters(time, resource);
+    d.__generate(begin(r), end(r), e);
+    stop_counters(time, resource);
+    report_performance(__FILE__, name+"-range"+suffix, time, resource);
+    clear_counters(time, resource);
+  }
+}
+
+template<typename Engine>
+void fill_with_uniform_ints(std::string name, Engine& e)
+{
+  using Dist = std::uniform_int_distribution<typename Engine::result_type>;
+  using param_type = typename Dist::param_type;
+
+  unsigned maxima[]{6, 10, 32, 100, 1000, 1024, (1<<16)-1, 1<<16, 1<<20, -1u};
+  for (auto hi : maxima)
+  {
+    Dist dist(param_type{0, hi});
+    std::ostringstream s;
+    s << name << "-uniform_int-" << (dist.max() - dist.min());
+    do_fill_with_uniform_ints(s.str(), dist, e);
+  }
+}
+
+int main()
+{
+  using namespace std;
+
+  std::mt19937 mt;
+  fill_with_uniform_ints("mt19937", mt);
+  std::mt19937_64 mt64;
+  fill_with_uniform_ints("mt19937_64", mt64);
+
+  // Same as std::mt19937 but using uint32_t not uint_fast32_t for result_type
+  using mt19937_32 = std::mersenne_twister_engine<uint32_t, 32, 624, 397, 31,
+                                                  0x9908b0df, 11, 0xffffffff,
+                                                  7, 0x9d2c5680, 15,
+                                                  0xefc60000, 18, 1812433253>;
+  mt19937_32 mt32;
+  fill_with_uniform_ints("mt19937_32", mt32);
+
+  std::minstd_rand0 lcg;
+  fill_with_uniform_ints("minstd_rand0", lcg);
+
+  // Same as std::minstd_rand0 but using uint32_t not uint_fast32_t
+  using minstd_rand0_32 = std::linear_congruential_engine<uint32_t, 48271, 0,
+                                                          2147483647>;
+  minstd_rand0_32 lcg_32;
+  fill_with_uniform_ints("minstd_rand0_32", lcg_32);
+
+  return 0;
+}
+