Add from_chars benchmark

Author: puji4810

benchmark/0022.from_chars/CMakeLists.txt

@@ -0,0 +1,24 @@
+include(FetchContent)
+
+FetchContent_Declare(
+  fast_float
+  GIT_REPOSITORY https://github.com/fastfloat/fast_float
+  GIT_TAG        main
+)
+FetchContent_MakeAvailable(fast_float)
+
+
+add_executable(benchmark.0022.from_chars ${CMAKE_CURRENT_LIST_DIR}/atoi_vs_from_chars.cc)
+target_include_directories(benchmark.0022.from_chars PRIVATE ${CMAKE_SOURCE_DIR}/include)
+
+target_compile_features(benchmark.0022.from_chars PRIVATE cxx_std_20)
+
+# Prefer official target if provided by fast_float; otherwise include headers directly
+if (TARGET fast_float::fast_float)
+  target_link_libraries(benchmark.0022.from_chars PRIVATE fast_float::fast_float)
+else()
+  FetchContent_GetProperties(fast_float)
+  if (fast_float_SOURCE_DIR)
+    target_include_directories(benchmark.0022.from_chars PRIVATE ${fast_float_SOURCE_DIR}/include)
+  endif()
+endif()

benchmark/0022.from_chars/atoi_vs_from_chars.cc

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+#include <fast_io.h>
+#include <fast_io_device.h>
+#include <fast_io_driver/timer.h>
+#include <vector>
+#include <string>
+#include </home/puji/fast_io/include/fast_io_dsal/string.h>
+#include <charconv>
+#include <fast_float/fast_float.h>
+
+using namespace fast_io::io;
+
+static std::string make_numbers_buffer(std::size_t n)
+{
+	std::string s;
+	s.reserve(n * 8);
+	for (std::size_t i{}; i != n; ++i)
+	{
+		auto old = s.size();
+		s.resize(old + 32);
+		auto *first = s.data() + old;
+		auto *last = s.data() + s.size();
+		auto res = std::to_chars(first, last - 1, i);
+		*res.ptr = '\n';
+		s.resize(res.ptr - s.data() + 1);
+	}
+	return s;
+}
+
+int main()
+{
+	constexpr std::size_t N = 10'000'000;
+	auto buf = make_numbers_buffer(N);
+	char const *begin = buf.data();
+	char const *end = buf.data() + buf.size();
+
+	{
+		std::size_t lines{};
+		for (char const *p = begin; p < end; ++p)
+		{
+			lines += (*p == '\n');
+		}
+		fast_io::println("lines=", lines);
+	}
+
+	// atoi
+	{
+		fast_io::timer t(u8"atoi");
+		std::uint64_t sum{};
+		char const *p = begin;
+		while (p < end)
+		{
+			int v = std::atoi(p);
+			sum += static_cast<std::uint64_t>(v);
+			while (p < end && *p >= '0' && *p <= '9')
+			{
+				++p;
+			}
+			if (p < end && *p == '\n')
+			{
+				++p;
+			}
+		}
+		std::uint64_t volatile sink = sum;
+		(void)sink;
+	}
+
+	// std::from_chars
+	{
+		fast_io::timer t(u8"std_from_chars");
+		std::uint64_t sum{};
+		char const *p = begin;
+		while (p < end)
+		{
+			std::uint64_t v{};
+			auto res = std::from_chars(p, end, v);
+			sum += v;
+			p = res.ptr;
+			if (p < end && *p == '\n')
+			{
+				++p;
+			}
+		}
+		std::uint64_t volatile sink = sum;
+		(void)sink;
+	}
+
+
+	// fast_io char_digit_to_literal
+	{
+		fast_io::timer t(u8"fastio_char_digit_to_literal");
+		std::uint64_t sum{};
+		char const *p = begin;
+		while (p < end)
+		{
+			using UCh = std::make_unsigned_t<char>;
+			std::uint64_t v{};
+			char const *q = p;
+			while (q < end && *q != '\n')
+			{
+				UCh ch = static_cast<UCh>(*q);
+				if (fast_io::details::char_digit_to_literal<10, char>(ch))
+				{
+					break;
+				}
+				v = v * 10 + static_cast<std::uint64_t>(ch);
+				++q;
+			}
+			sum += v;
+			p = (q < end ? q + 1 : q);
+		}
+		std::uint64_t volatile sink = sum;
+		(void)sink;
+	}
+
+	// fast_float
+	{
+		fast_io::timer t(u8"fast_float_from_chars");
+		std::uint64_t sum{};
+		char const *p = begin;
+		while (p < end)
+		{
+			std::uint64_t v{};
+			auto res = fast_float::from_chars(p, end, v);
+			sum += v;
+			p = res.ptr;
+			if (p < end && *p == '\n')
+			{
+				++p;
+			}
+		}
+		std::uint64_t volatile sink = sum;
+		(void)sink;
+	}
+
+}