SDL Performance Counter vs Ticks

SDL_GetPerformanceCounter() and SDL_GetTicks64() are both functions provided by SDL for timing purposes, but they serve different needs and have distinct characteristics:

The main difference lies in their resolution. SDL_GetPerformanceCounter() offers a higher resolution timer, often at the nanosecond level, while SDL_GetTicks64() provides millisecond precision.

1#include <SDL.h>
2#include <iostream>
3
4int main(int argc, char** argv) {
5  SDL_Init(SDL_INIT_TIMER);
6
7  Uint64 perfCounterStart{
8    SDL_GetPerformanceCounter()};
9  Uint64 ticksStart{SDL_GetTicks64()};
10
11  // Simulate some work
12  for (int i{0}; i < 1000; ++i) {
13    std::cout << "Working...\n";
14  }
15
16  Uint64 perfCounterEnd{
17    SDL_GetPerformanceCounter()};
18  Uint64 ticksEnd{SDL_GetTicks64()};
19
20  std::cout << "Performance Counter delta: "
21    << perfCounterEnd - perfCounterStart
22    << "\nTicks delta: "
23    << ticksEnd - ticksStart << '\n';
24
25  SDL_Quit();
26  return 0;
27}

1...
2Working...
3Working...
4Working...
5Performance Counter delta: 413164
6Ticks delta: 41

In this example, you can see that the performance counter captures a much more precise time difference.

SDL_GetTicks64() always returns milliseconds, making it straightforward to use. However, SDL_GetPerformanceCounter() returns platform-specific units, requiring conversion using SDL_GetPerformanceFrequency() to get meaningful time intervals:

1#include <SDL.h>
2#include <iostream>
3
4int main(int argc, char** argv) {
5  SDL_Init(SDL_INIT_TIMER);
6
7  Uint64 perfCounterStart{
8    SDL_GetPerformanceCounter()};
9  // Simulate some work
10  for (int i{0}; i < 1000; ++i) {
11    std::cout << "Working...\n";
12  }
13  Uint64 perfCounterEnd{
14    SDL_GetPerformanceCounter()};
15
16  double secondsElapsed{
17    static_cast<double>(perfCounterEnd -
18      perfCounterStart) /
19    SDL_GetPerformanceFrequency()};
20
21  std::cout << "Seconds elapsed: " <<
22    secondsElapsed << '\n';
23
24  SDL_Quit();
25  return 0;
26}

1...
2Working...
3Working...
4Working...
5Seconds elapsed: 0.0456831

SDL_GetTicks64() is suitable for general timing needs, like measuring longer intervals or implementing game logic that doesn't require extreme precision. SDL_GetPerformanceCounter() is ideal for high-precision timing, such as frame time calculations, performance profiling, or implementing smooth animations.

In game development, you might use SDL_GetPerformanceCounter() for your main game loop timing, while SDL_GetTicks64() could be used for less critical timings like cooldowns or periodic events.