/*

 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

#include "precompiled.hpp"

#include "libadt/vectset.hpp"

#include "runtime/os.hpp"

#include "utilities/population_count.hpp"

#include "utilities/globalDefinitions.hpp"

#include "unittest.hpp"

TEST(population_count, sparse) {

  extern uint8_t bitsInByte[BITS_IN_BYTE_ARRAY_SIZE];

  // Step through the entire input range from a random starting point,

  // verify population_count return values against the lookup table

  // approach used historically

  uint32_t step = 4711;

  for (uint32_t value = os::random() % step; value < UINT_MAX - step; value += step) {

    uint32_t lookup = bitsInByte[(value >> 24) & 0xff] +

                      bitsInByte[(value >> 16) & 0xff] +

                      bitsInByte[(value >> 8)  & 0xff] +

                      bitsInByte[ value        & 0xff];

    EXPECT_EQ(lookup, population_count(value))

        << "value = " << value;

  }

  // Test a few edge cases

  EXPECT_EQ(0u, population_count(0u))

      << "value = " << 0;

  EXPECT_EQ(1u, population_count(1u))

      << "value = " << 1;

  EXPECT_EQ(1u, population_count(2u))

      << "value = " << 2;

  EXPECT_EQ(32u, population_count(UINT_MAX))

      << "value = " << UINT_MAX;

  EXPECT_EQ(31u, population_count(UINT_MAX - 1))

      << "value = " << (UINT_MAX - 1);

}