From 06719ae42f10d4152780b75173e32fb6f4bb7633 Mon Sep 17 00:00:00 2001
From: "Thiago Marcos P. Santos" <tmpsantos@gmail.com>
Date: Wed, 12 Jul 2017 14:09:59 +0300
Subject: [PATCH] [benchmark] Add a benchmark for our dtoa implementation

Make sure it is faster than std::to_value(). And it is, by ~30% for
the normal use case, and much faster when close to the double limits.

util::dtoa also offers a much better precision.
---
 benchmark/fixtures/api/cache.db   | Bin 1298432 -> 1298432 bytes
 benchmark/util/dtoa.benchmark.cpp |  66 ++++++++++++++++++++++++++++++
 cmake/benchmark-files.cmake       |   3 ++
 3 files changed, 69 insertions(+)
 create mode 100644 benchmark/util/dtoa.benchmark.cpp

diff --git a/benchmark/fixtures/api/cache.db b/benchmark/fixtures/api/cache.db
index c2ada1fbd5b738eae732ff87ad0fac3ff6f6ed24..6a1d60421f8d0ff10f9ec399642b39cf7af8c148 100644
GIT binary patch
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diff --git a/benchmark/util/dtoa.benchmark.cpp b/benchmark/util/dtoa.benchmark.cpp
new file mode 100644
index 000000000..0009c6dd1
--- /dev/null
+++ b/benchmark/util/dtoa.benchmark.cpp
@@ -0,0 +1,66 @@
+#include <benchmark/benchmark.h>
+
+#include <mbgl/util/dtoa.hpp>
+
+#include <cfloat>
+#include <cmath>
+
+using namespace mbgl;
+
+static void Util_dtoa(::benchmark::State& state) {
+    while (state.KeepRunning()) {
+        util::dtoa(0.);
+        util::dtoa(M_E);
+        util::dtoa(M_LOG2E);
+        util::dtoa(M_LOG10E);
+        util::dtoa(M_LN2);
+        util::dtoa(M_LN10);
+        util::dtoa(M_PI);
+        util::dtoa(M_PI_2);
+        util::dtoa(M_PI_4);
+        util::dtoa(M_1_PI);
+        util::dtoa(M_2_PI);
+        util::dtoa(M_2_SQRTPI);
+        util::dtoa(M_SQRT2);
+        util::dtoa(M_SQRT1_2);
+    }
+}
+
+static void Util_standardDtoa(::benchmark::State& state) {
+    while (state.KeepRunning()) {
+        std::to_string(0.);
+        std::to_string(M_E);
+        std::to_string(M_LOG2E);
+        std::to_string(M_LOG10E);
+        std::to_string(M_LN2);
+        std::to_string(M_LN10);
+        std::to_string(M_PI);
+        std::to_string(M_PI_2);
+        std::to_string(M_PI_4);
+        std::to_string(M_1_PI);
+        std::to_string(M_2_PI);
+        std::to_string(M_2_SQRTPI);
+        std::to_string(M_SQRT2);
+        std::to_string(M_SQRT1_2);
+    }
+}
+
+static void Util_dtoaLimits(::benchmark::State& state) {
+    while (state.KeepRunning()) {
+        util::dtoa(DBL_MIN);
+        util::dtoa(DBL_MAX);
+    }
+}
+
+static void Util_standardDtoaLimits(::benchmark::State& state) {
+    while (state.KeepRunning()) {
+        std::to_string(DBL_MIN);
+        std::to_string(DBL_MAX);
+    }
+}
+
+BENCHMARK(Util_dtoa);
+BENCHMARK(Util_standardDtoa);
+
+BENCHMARK(Util_dtoaLimits);
+BENCHMARK(Util_standardDtoaLimits);
diff --git a/cmake/benchmark-files.cmake b/cmake/benchmark-files.cmake
index 35931a6b5..6fb9a80d5 100644
--- a/cmake/benchmark-files.cmake
+++ b/cmake/benchmark-files.cmake
@@ -19,4 +19,7 @@ set(MBGL_BENCHMARK_FILES
     benchmark/src/mbgl/benchmark/benchmark.cpp
     benchmark/src/mbgl/benchmark/util.cpp
     benchmark/src/mbgl/benchmark/util.hpp
+
+    # util
+    benchmark/util/dtoa.benchmark.cpp
 )