1 files changed, 61 insertions, 0 deletions
diff --git a/gcc-4.9/libstdc++-v3/testsuite/20_util/hash/chi2_q_bit_flip_set.cc b/gcc-4.9/libstdc++-v3/testsuite/20_util/hash/chi2_q_bit_flip_set.cc
new file mode 100644
index 000000000..600dd730d
--- /dev/null
+++ b/gcc-4.9/libstdc++-v3/testsuite/20_util/hash/chi2_q_bit_flip_set.cc
@@ -0,0 +1,61 @@
+// { dg-options "-std=gnu++0x" }
+// Use smaller statistics when running on simulators, so it takes less time.
+// { dg-options "-std=gnu++0x -DSAMPLES=30000" { target simulator } }
+
+// Copyright (C) 2010-2014 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 "chi2_quality.h"
+
+// Tests chi^2 for a distribution of strings that differ from each
+// other by only a few bits. We start with an arbitrary base string, and
+// flip three random bits for each member of the set.
+void
+test_bit_flip_set()
+{
+  bool test __attribute__((unused)) = true;
+  const unsigned long N = SAMPLES;
+  const unsigned long k = N/100;
+  const unsigned int len = 67;
+  const unsigned int bitlen = len * 8;
+  const unsigned int bits_to_flip = 3;
+  const char base[len+1] = "abcdefghijklmnopqrstuvwxyz"
+                           "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+                           "0123456789!@#$%";
+
+  std::unordered_set<std::string> set;
+  while (set.size() < N)
+    {
+      std::string s(base, base+len);
+      for (unsigned int i = 0; i < bits_to_flip; ++i)
+        {
+          int bit = rand() % bitlen;
+          s[bit/8] ^= (1 << (bit%8));
+        }
+      set.insert(s);
+    }
+
+  double chi2 = chi2_hash(set, k);
+  VERIFY( chi2 < k*1.1 );
+}
+
+int
+main()
+{
+  test_bit_flip_set();
+  return 0;
+}