my_murmur3-t.cc

/* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.

   This program 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; version 2 of the License.

   This program 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 program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */


// First include (the generated) my_config.h, to get correct platform defines.
#include "my_config.h"
#include <gtest/gtest.h>

#include "my_murmur3.h"

/*
  Putting everything in a namespace prevents any (unintentional)
  name clashes with the code under test.
*/

namespace murmur3_unittest {

/* Simple test checking that hash for fixed key has correct value. */

TEST(Murmur3, Basic)
{
  const char *str= "To be, or not to be, that is the question;";

  uint hash= murmur3_32((uchar*)str, strlen(str), 0);
  EXPECT_EQ(2385370181U, hash);
}


/* Test for empty key. */

TEST(Murmur3, Empty)
{
  uint hash= murmur3_32(NULL, 0, 0);
  EXPECT_EQ(0U, hash);
}


/*
  Test that shows that when we hash zero-keys of different length we
  get different results. Our my_hash_sort_bin is not good at that.
*/

TEST(Murmur3, Zeroes)
{
  uchar buff[32];
  memset(buff, 0, sizeof(buff));

  uint hash1= murmur3_32(buff, sizeof(buff)/2, 0);
  uint hash2= murmur3_32(buff, sizeof(buff), 0);
  EXPECT_NE(hash1, hash2);
}


/* Test that seed matters. */

TEST(Murmur3, Seed)
{
  const char *str= "Whether 'tis nobler in the mind to suffer";

  uint hash1= murmur3_32((uchar *)str, strlen(str), 0);
  uint hash2= murmur3_32((uchar *)str, strlen(str), 1);
  EXPECT_NE(hash1, hash2);
}


/*
  Test for bug #16396598 "MDL HASH CAN STILL BE CONCURRENCY BOTTLENECK".
  Hashes for 8 keys from the bug report should have sufficiently different
  lower bits, so corresponding MDL objects won't fall into the same MDL map
  partitions.
*/

TEST(Murmur3, Bug16396598)
{
  const char keys[8][14]= {"\002test\000sbtest1", "\002test\000sbtest2",
                           "\002test\000sbtest3", "\002test\000sbtest4",
                           "\002test\000sbtest5", "\002test\000sbtest6",
                           "\002test\000sbtest7", "\002test\000sbtest8" };
  /* Array for number of keys falling into n-th bucket. */
  uint buckets[8];
  int i;

  memset(buckets, 0, sizeof(buckets));

  for (i= 0; i < 8; ++i)
    buckets[murmur3_32((const uchar *)keys[i], sizeof(keys[0]), 0) % 8]++;

  /*
    It is OK for a few keys to fall into the same bucket.
    But not for the half of the keys.
  */
  for (i= 0; i < 8; ++i)
    EXPECT_GT(4U, buckets[i]);
}

}  // namespace