inline bool f1ni(int i) {
  return i % 2 == 0;
}

TEST(OptionalTest, TestOptionalPerf) {
  auto f2 = [](int i) -> std::optional<int> {
    if (i % 2 == 0) {
      return {};
    }
    return i + 1;
  };

  // run 1M cycles
  constexpr auto cycles = 100000000;
  nebula::common::Evidence::Duration duration;
  long sum2 = 0;
  for (int i = 0; i < cycles; ++i) {
    auto x = f2(i);
    if (x) {
      sum2 += x.value();
    }
  }
  LOG(INFO) << fmt::format("optional approach: sum={0}, time={1}", sum2, duration.elapsedMs());

  duration.reset();
  long sum1 = 0;
  for (int i = 0; i < cycles; ++i) {
    if (i % 2 != 0) {
      sum1 += f1(i);
    }
  }
  LOG(INFO) << fmt::format("special value approach: sum={0}, time={1}", sum1, duration.elapsedMs());
  EXPECT_EQ(sum1, sum2);

--------------------------
Laptop Mac MacOs Mojave 
Processor 2.6 GHz Intel Core i7
/usr/bin/g++ --version
> Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1
> Apple LLVM version 10.0.1 (clang-1001.0.46.4)
> Target: x86_64-apple-darwin18.7.0
> Thread model: posix
> InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

[Test Output]
I0812 09:36:20.678683 348009920 TestCommon.cpp:354] optional approach: sum=2500000050000000, time=13
I0812 09:36:20.692001 348009920 TestCommon.cpp:363] special value approach: sum=2500000050000000, time=12

Linux Ubuntu 18.04 LTS
36 cores - one of them
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 85
model name      : Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz
stepping        : 4
microcode       : 0x100014a
cpu MHz         : 1685.329
cache size      : 25344 KB
physical id     : 0
siblings        : 36
core id         : 0
cpu cores       : 18
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq monitor ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single pti fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx avx512f avx512dq rdseed adx smap clflushopt clwb avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves ida arat pku ospke


/usr/bin/g++ --version
> g++ (Ubuntu 9.1.0-2ubuntu2~18.04) 9.1.0
> Copyright (C) 2019 Free Software Foundation, Inc.

[Test Output]
I0812 16:42:07.391607 15080 TestCommon.cpp:354] optional approach: sum=2500000050000000, time=59
I0812 16:42:07.473335 15080 TestCommon.cpp:363] special value approach: sum=2500000050000000, time=81