folly/test/BitsTest.cpp

   1 /*
   2  * Copyright 2014 Facebook, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *   http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 // @author Tudor Bosman (tudorb@fb.com)
  18
  19 #include <gflags/gflags.h>
  20 #include <folly/Bits.h>
  21 #include <folly/Benchmark.h>
  22 #include <gtest/gtest.h>
  23
  24 using namespace folly;
  25
  26 // Test constexpr-ness.
  27 #ifndef __clang__
  28 static_assert(findFirstSet(2u) == 2, "findFirstSet");
  29 static_assert(findLastSet(2u) == 2, "findLastSet");
  30 static_assert(nextPowTwo(2u) == 2, "nextPowTwo");
  31 static_assert(isPowTwo(2u), "isPowTwo");
  32 #endif  // __clang__
  33
  34 namespace {
  35
  36 template <class INT>
  37 void testFFS() {
  38   EXPECT_EQ(0, findFirstSet(static_cast<INT>(0)));
  39   size_t bits = std::numeric_limits<
  40     typename std::make_unsigned<INT>::type>::digits;
  41   for (size_t i = 0; i < bits; i++) {
  42     INT v = (static_cast<INT>(1) << (bits - 1)) |
  43             (static_cast<INT>(1) << i);
  44     EXPECT_EQ(i+1, findFirstSet(v));
  45   }
  46 }
  47
  48 template <class INT>
  49 void testFLS() {
  50   typedef typename std::make_unsigned<INT>::type UINT;
  51   EXPECT_EQ(0, findLastSet(static_cast<INT>(0)));
  52   size_t bits = std::numeric_limits<UINT>::digits;
  53   for (size_t i = 0; i < bits; i++) {
  54     INT v1 = static_cast<UINT>(1) << i;
  55     EXPECT_EQ(i + 1, findLastSet(v1));
  56
  57     INT v2 = (static_cast<UINT>(1) << i) - 1;
  58     EXPECT_EQ(i, findLastSet(v2));
  59   }
  60 }
  61
  62 }  // namespace
  63
  64 TEST(Bits, FindFirstSet) {
  65   testFFS<char>();
  66   testFFS<signed char>();
  67   testFFS<unsigned char>();
  68   testFFS<short>();
  69   testFFS<unsigned short>();
  70   testFFS<int>();
  71   testFFS<unsigned int>();
  72   testFFS<long>();
  73   testFFS<unsigned long>();
  74   testFFS<long long>();
  75   testFFS<unsigned long long>();
  76 }
  77
  78 TEST(Bits, FindLastSet) {
  79   testFLS<char>();
  80   testFLS<signed char>();
  81   testFLS<unsigned char>();
  82   testFLS<short>();
  83   testFLS<unsigned short>();
  84   testFLS<int>();
  85   testFLS<unsigned int>();
  86   testFLS<long>();
  87   testFLS<unsigned long>();
  88   testFLS<long long>();
  89   testFLS<unsigned long long>();
  90 }
  91
  92 #define testPowTwo(nextPowTwoFunc) {                              \
  93   EXPECT_EQ(1, nextPowTwoFunc(0u));                               \
  94   EXPECT_EQ(1, nextPowTwoFunc(1u));                               \
  95   EXPECT_EQ(2, nextPowTwoFunc(2u));                               \
  96   EXPECT_EQ(4, nextPowTwoFunc(3u));                               \
  97   EXPECT_EQ(4, nextPowTwoFunc(4u));                               \
  98   EXPECT_EQ(8, nextPowTwoFunc(5u));                               \
  99   EXPECT_EQ(8, nextPowTwoFunc(6u));                               \
 100   EXPECT_EQ(8, nextPowTwoFunc(7u));                               \
 101   EXPECT_EQ(8, nextPowTwoFunc(8u));                               \
 102   EXPECT_EQ(16, nextPowTwoFunc(9u));                              \
 103   EXPECT_EQ(16, nextPowTwoFunc(13u));                             \
 104   EXPECT_EQ(16, nextPowTwoFunc(16u));                             \
 105   EXPECT_EQ(512, nextPowTwoFunc(510u));                           \
 106   EXPECT_EQ(512, nextPowTwoFunc(511u));                           \
 107   EXPECT_EQ(512, nextPowTwoFunc(512u));                           \
 108   EXPECT_EQ(1024, nextPowTwoFunc(513u));                          \
 109   EXPECT_EQ(1024, nextPowTwoFunc(777u));                          \
 110   EXPECT_EQ(1ul << 31, nextPowTwoFunc((1ul << 31) - 1));          \
 111   EXPECT_EQ(1ul << 32, nextPowTwoFunc((1ul << 32) - 1));          \
 112   EXPECT_EQ(1ull << 63, nextPowTwoFunc((1ull << 62) + 1));        \
 113 }
 114
 115
 116 TEST(Bits, nextPowTwoClz) {
 117   testPowTwo(nextPowTwo);
 118 }
 119
 120 BENCHMARK(nextPowTwoClz, iters) {
 121   for (unsigned long i = 0; i < iters; ++i) {
 122     auto x = folly::nextPowTwo(iters);
 123     folly::doNotOptimizeAway(x);
 124   }
 125 }
 126
 127 TEST(Bits, isPowTwo) {
 128   EXPECT_FALSE(isPowTwo(0u));
 129   EXPECT_TRUE(isPowTwo(1ul));
 130   EXPECT_TRUE(isPowTwo(2ull));
 131   EXPECT_FALSE(isPowTwo(3ul));
 132   EXPECT_TRUE(isPowTwo(4ul));
 133   EXPECT_FALSE(isPowTwo(5ul));
 134   EXPECT_TRUE(isPowTwo(8ul));
 135   EXPECT_FALSE(isPowTwo(15u));
 136   EXPECT_TRUE(isPowTwo(16u));
 137   EXPECT_FALSE(isPowTwo(17u));
 138   EXPECT_FALSE(isPowTwo(511ul));
 139   EXPECT_TRUE(isPowTwo(512ul));
 140   EXPECT_FALSE(isPowTwo(513ul));
 141   EXPECT_FALSE(isPowTwo((1ul<<31) - 1));
 142   EXPECT_TRUE(isPowTwo(1ul<<31));
 143   EXPECT_FALSE(isPowTwo((1ul<<31) + 1));
 144   EXPECT_FALSE(isPowTwo((1ull<<63) - 1));
 145   EXPECT_TRUE(isPowTwo(1ull<<63));
 146   EXPECT_FALSE(isPowTwo((1ull<<63) + 1));
 147 }
 148
 149 BENCHMARK_DRAW_LINE();
 150 BENCHMARK(isPowTwo, iters) {
 151   bool b;
 152   for (unsigned long i = 0; i < iters; ++i) {
 153     b = folly::isPowTwo(i);
 154     folly::doNotOptimizeAway(b);
 155   }
 156 }
 157
 158 TEST(Bits, popcount) {
 159   EXPECT_EQ(0, popcount(0U));
 160   EXPECT_EQ(1, popcount(1U));
 161   EXPECT_EQ(32, popcount(uint32_t(-1)));
 162   EXPECT_EQ(64, popcount(uint64_t(-1)));
 163 }
 164
 165 int main(int argc, char** argv) {
 166   testing::InitGoogleTest(&argc, argv);
 167   gflags::ParseCommandLineFlags(&argc, &argv, true);
 168   auto ret = RUN_ALL_TESTS();
 169   if (!ret && FLAGS_benchmark) {
 170     folly::runBenchmarks();
 171   }
 172   return ret;
 173 }
 174
 175 /*
 176 Benchmarks run on dual Xeon X5650's @ 2.67GHz w/hyperthreading enabled
 177   (12 physical cores, 12 MB cache, 72 GB RAM)
 178
 179 Benchmark                               Iters   Total t    t/iter iter/sec
 180 ------------------------------------------------------------------------------
 181 *       nextPowTwoClz                 1000000  1.659 ms  1.659 ns  574.8 M
 182 */