folly/test/BitsTest.cpp

   1 /*
   2  * Copyright 2012 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 namespace {
  27
  28 template <class INT>
  29 void testFFS() {
  30   EXPECT_EQ(0, findFirstSet(static_cast<INT>(0)));
  31   size_t bits = std::numeric_limits<
  32     typename std::make_unsigned<INT>::type>::digits;
  33   for (size_t i = 0; i < bits; i++) {
  34     INT v = (static_cast<INT>(1) << (bits - 1)) |
  35             (static_cast<INT>(1) << i);
  36     EXPECT_EQ(i+1, findFirstSet(v));
  37   }
  38 }
  39
  40 template <class INT>
  41 unsigned int findLastSetPortable(INT x) {
  42   return detail::findLastSetPortable(
  43       static_cast<typename std::make_unsigned<INT>::type>(x));
  44 }
  45
  46 template <class INT>
  47 void testFLS() {
  48   typedef typename std::make_unsigned<INT>::type UINT;
  49   EXPECT_EQ(0, findLastSet(static_cast<INT>(0)));
  50   size_t bits = std::numeric_limits<UINT>::digits;
  51   for (size_t i = 0; i < bits; i++) {
  52     INT v1 = static_cast<UINT>(1) << i;
  53     EXPECT_EQ(i + 1, findLastSet(v1));
  54     EXPECT_EQ(i + 1, findLastSetPortable(v1));
  55
  56     INT v2 = (static_cast<UINT>(1) << i) - 1;
  57     EXPECT_EQ(i, findLastSet(v2));
  58     EXPECT_EQ(i, findLastSetPortable(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 #ifdef __GNUC__
 117
 118 TEST(Bits, nextPowTwoClz) {
 119   testPowTwo(nextPowTwo);
 120 }
 121
 122 int x; // prevent the loop from getting optimized away
 123 BENCHMARK(nextPowTwoClz, iters) {
 124   x = folly::nextPowTwo(iters);
 125 }
 126
 127 #endif
 128
 129 TEST(Bits, nextPowTwoPortable) {
 130   testPowTwo(detail::nextPowTwoPortable);
 131 }
 132
 133 BENCHMARK(nextPowTwoPortable, iters) {
 134   x = detail::nextPowTwoPortable(iters);
 135 }
 136
 137 BENCHMARK_DRAW_LINE();
 138
 139 int main(int argc, char** argv) {
 140   testing::InitGoogleTest(&argc, argv);
 141   google::ParseCommandLineFlags(&argc, &argv, true);
 142   auto ret = RUN_ALL_TESTS();
 143   if (!ret && FLAGS_benchmark) {
 144     folly::runBenchmarks();
 145   }
 146   return ret;
 147 }
 148
 149 /*
 150 Benchmarks run on dual Xeon X5650's @ 2.67GHz w/hyperthreading enabled
 151   (12 physical cores, 12 MB cache, 72 GB RAM)
 152
 153 Benchmark                               Iters   Total t    t/iter iter/sec
 154 ------------------------------------------------------------------------------
 155 *       nextPowTwoClz                 1000000  1.659 ms  1.659 ns  574.8 M
 156  +66.8% nextPowTwoPortable            1000000  2.767 ms  2.767 ns  344.7 M
 157 */