Benchmark std::to_string vs. folly::to<std::string>

Summary: We wanted to compare the benefits of using folly::to<std::string> directly, and decided this benchmarking might as well be contributed back to folly.  Here are the results:

```
  ============================================================================
  folly/test/ConvTest.cpp                         relative  time/iter  iters/s
  ============================================================================
  ...
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(1)                                  157.88ns    6.33M
  u64ToStringFollyMeasure(1)                       212.52%    74.29ns   13.46M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(12)                                 158.14ns    6.32M
  u64ToStringFollyMeasure(12)                      212.55%    74.40ns   13.44M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(123)                                152.26ns    6.57M
  u64ToStringFollyMeasure(123)                     210.95%    72.18ns   13.85M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(1234)                               152.40ns    6.56M
  u64ToStringFollyMeasure(1234)                    204.82%    74.41ns   13.44M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(12345)                              156.01ns    6.41M
  u64ToStringFollyMeasure(12345)                   208.90%    74.68ns   13.39M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(123456)                             178.21ns    5.61M
  u64ToStringFollyMeasure(123456)                  238.77%    74.63ns   13.40M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(1234567)                            161.38ns    6.20M
  u64ToStringFollyMeasure(1234567)                 203.09%    79.46ns   12.58M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(12345678)                           159.01ns    6.29M
  u64ToStringFollyMeasure(12345678)                192.42%    82.64ns   12.10M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(123456789)                          169.07ns    5.91M
  u64ToStringFollyMeasure(123456789)               203.70%    83.00ns   12.05M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(1234567890)                         166.56ns    6.00M
  u64ToStringFollyMeasure(1234567890)              187.21%    88.97ns   11.24M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(12345678901)                        176.22ns    5.67M
  u64ToStringFollyMeasure(12345678901)             197.57%    89.20ns   11.21M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(123456789012)                       174.74ns    5.72M
  u64ToStringFollyMeasure(123456789012)            182.52%    95.74ns   10.45M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(1234567890123)                      178.47ns    5.60M
  u64ToStringFollyMeasure(1234567890123)           186.81%    95.54ns   10.47M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(12345678901234)                     187.33ns    5.34M
  u64ToStringFollyMeasure(12345678901234)          184.05%   101.78ns    9.82M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(123456789012345)                    198.16ns    5.05M
  u64ToStringFollyMeasure(123456789012345)         182.48%   108.59ns    9.21M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(1234567890123456)                   182.56ns    5.48M
  u64ToStringFollyMeasure(1234567890123456)        164.19%   111.19ns    8.99M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(12345678901234567)                  186.80ns    5.35M
  u64ToStringFollyMeasure(12345678901234567)       162.33%   115.07ns    8.69M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(123456789012345678)                 195.08ns    5.13M
  u64ToStringFollyMeasure(123456789012345678)      165.51%   117.87ns    8.48M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(1234567890123456789)                200.27ns    4.99M
  u64ToStringFollyMeasure(1234567890123456789)     164.62%   121.65ns    8.22M
  ----------------------------------------------------------------------------
  u64ToStringClibMeasure(12345678901234567890U)              203.18ns    4.92M
  u64ToStringFollyMeasure(12345678901234567890U)   162.38%   125.13ns    7.99M
  ----------------------------------------------------------------------------
  ...
  ============================================================================
```

Reviewed By: yfeldblum

Differential Revision: D2680998

fb-gh-sync-id: 179fbd756c714c92b7230d3750af024865ecbb0a

diff --git a/folly/test/ConvTest.cpp b/folly/test/ConvTest.cpp
index 8967a7d0f0a454a66739a1de33b2467a4d4a5fd9..3cf6d5b8a06e735894bfb5175b6b458dbf8eab01 100644 (file)
--- a/folly/test/ConvTest.cpp
+++ b/folly/test/ConvTest.cpp
@@ -1021,6 +1021,22 @@ void u64ToAsciiFollyBM(unsigned int n, uint64_t value) {
   }
 }
 
+// Benchmark unsigned to string conversion
+
+void u64ToStringClibMeasure(unsigned int n, uint64_t value) {
+  // FOLLY_RANGE_CHECK_TO_STRING expands to std::to_string, except on Android
+  // where std::to_string is not supported
+  FOR_EACH_RANGE (i, 0, n) {
+    FOLLY_RANGE_CHECK_TO_STRING(value + n);
+  }
+}
+
+void u64ToStringFollyMeasure(unsigned int n, uint64_t value) {
+  FOR_EACH_RANGE (i, 0, n) {
+    to<std::string>(value + n);
+  }
+}
+
 // Benchmark uitoa with string append
 
 void u2aAppendClassicBM(unsigned int n, uint64_t value) {
@@ -1130,6 +1146,34 @@ DEFINE_BENCHMARK_GROUP(12345678901234567890U);
 
 #undef DEFINE_BENCHMARK_GROUP
 
+#define DEFINE_BENCHMARK_GROUP(n)                        \
+  BENCHMARK_PARAM(u64ToStringClibMeasure, n);            \
+  BENCHMARK_RELATIVE_PARAM(u64ToStringFollyMeasure, n);  \
+  BENCHMARK_DRAW_LINE();
+
+DEFINE_BENCHMARK_GROUP(1);
+DEFINE_BENCHMARK_GROUP(12);
+DEFINE_BENCHMARK_GROUP(123);
+DEFINE_BENCHMARK_GROUP(1234);
+DEFINE_BENCHMARK_GROUP(12345);
+DEFINE_BENCHMARK_GROUP(123456);
+DEFINE_BENCHMARK_GROUP(1234567);
+DEFINE_BENCHMARK_GROUP(12345678);
+DEFINE_BENCHMARK_GROUP(123456789);
+DEFINE_BENCHMARK_GROUP(1234567890);
+DEFINE_BENCHMARK_GROUP(12345678901);
+DEFINE_BENCHMARK_GROUP(123456789012);
+DEFINE_BENCHMARK_GROUP(1234567890123);
+DEFINE_BENCHMARK_GROUP(12345678901234);
+DEFINE_BENCHMARK_GROUP(123456789012345);
+DEFINE_BENCHMARK_GROUP(1234567890123456);
+DEFINE_BENCHMARK_GROUP(12345678901234567);
+DEFINE_BENCHMARK_GROUP(123456789012345678);
+DEFINE_BENCHMARK_GROUP(1234567890123456789);
+DEFINE_BENCHMARK_GROUP(12345678901234567890U);
+
+#undef DEFINE_BENCHMARK_GROUP
+
 #define DEFINE_BENCHMARK_GROUP(n)                       \
   BENCHMARK_PARAM(clibAtoiMeasure, n);                  \
   BENCHMARK_RELATIVE_PARAM(lexicalCastMeasure, n);      \