Created
August 12, 2019 16:44
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understand perf of std::optional
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| 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 |
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