vectortest.cpp

// g++ vectortest.cpp
/*
	emplace_back: 553305 ticks
	push_back: 665359 ticks
	resize: 437487 ticks
*/
// g++ -O3 -ffast-math vectortest.cpp
/*
	emplace_back: 165961 ticks
	push_back: 165695 ticks
	resize: 87059 ticks
*/

#include <iostream>
#include <vector>
#include <ctime>
#include <cstdint>

#define LOG(what, start, end) \
	(end) = clock(); \
	std::cout << (what) << ((end) - (start)) << " ticks" << std::endl;

inline void write4bytes(uint8_t *data)
{
	data[0] = 12;
	data[1] = 75;
	data[2] = 22;
	data[3] = 132;
}

int main()
{
	clock_t start, end;
	uint32_t i;
	{
		// Pre-heat a little
		std::vector<uint8_t> buf;
		for (i = 0; i < 1000000; ++i)
			buf.push_back((uint8_t)i);
	}

	{
		std::vector<uint8_t> buf;
		start = clock();
		for (i = 0; i < 1000000; ++i) {
			buf.emplace_back(1);
			buf.emplace_back(5);
			buf.emplace_back(8);
			buf.emplace_back(2);
			buf.emplace_back(52);
			buf.emplace_back(122);
			buf.emplace_back(240);
			buf.emplace_back(235);
			buf.emplace_back(34);
			buf.emplace_back(182); // 10

			buf.emplace_back(1);
			buf.emplace_back(5);
			buf.emplace_back(8);
			buf.emplace_back(2);
			buf.emplace_back(52);
			buf.emplace_back(122);
			buf.emplace_back(240);
			buf.emplace_back(235);
			buf.emplace_back(34);
			buf.emplace_back(182); // 20
		}
		LOG("emplace_back: ", start, end)
	}
	{
		std::vector<uint8_t> buf;
		start = clock();
		for (i = 0; i < 1000000; ++i) {
			buf.push_back(1);
			buf.push_back(5);
			buf.push_back(8);
			buf.push_back(2);
			buf.push_back(52);
			buf.push_back(122);
			buf.push_back(240);
			buf.push_back(235);
			buf.push_back(34);
			buf.push_back(182); // 10

			buf.push_back(1);
			buf.push_back(5);
			buf.push_back(8);
			buf.push_back(2);
			buf.push_back(52);
			buf.push_back(122);
			buf.push_back(240);
			buf.push_back(235);
			buf.push_back(34);
			buf.push_back(182); // 20
		}
		LOG("push_back: ", start, end)
	}

	{
		std::vector<uint8_t> buf;
		start = clock();
		uint32_t bufsize = 0;
		for (i = 0; i < 1000000; ++i) {
			buf.resize(bufsize + 4);
			write4bytes(&buf[bufsize]);
			bufsize += 4;

			buf.resize(bufsize + 4);
			write4bytes(&buf[bufsize]);
			bufsize += 4;

			buf.resize(bufsize + 4);
			write4bytes(&buf[bufsize]);
			bufsize += 4;

			buf.resize(bufsize + 4);
			write4bytes(&buf[bufsize]);
			bufsize += 4;

			buf.resize(bufsize + 4);
			write4bytes(&buf[bufsize]);
			bufsize += 4;
		}
		LOG("resize: ", start, end)
	}
	return 0;
}