Getting millisecond elapsed time using Bebbo's Amiga GCC toolchain

[NovaCoder]

Hi,

Wonder if anyone can help.

I need a fast way to tack how much time has passed in my main loop.

I normally use https://www.tutorialspoint.com/c_sta...tion_clock.htm which has a high frequency on the old GCC 3.4 (milliseconds) but in my Bebbo build it seems to be limited to 50fps.

I've hacked together the following code but I'm not really sure it's the best way to do it.

	gettimeofday(&lastFrameTime, NULL);

	while (true) {
		gettimeofday(&currentFrameTime, NULL);

	    double elapsedtime = (currentFrameTime.tv_sec - lastFrameTime.tv_sec) * 1000.0;      // sec to ms
	    elapsedtime += (currentFrameTime.tv_usec - lastFrameTime.tv_usec) / 1000.0;          // us to ms


		// Capture user input and update object positions.
		g_world->updateWorld(elapsedtime / 1000);
		g_world->updateFrame();


		memcpy(&lastFrameTime, &currentFrameTime, sizeof(struct timeval));
	}

Thanks

[Ernst Blofeld]

I don't have a lot of context, but if you're limited to 50 fps, maybe you're using the wrong CIA timer in your gettimeofday?

Anyway, in case it helps, this is how I do it, having taken over the system:

ULONG GetCurrentTime(void) {
    ULONG hi = ciab->ciatodhi;		// latch activated
    ULONG mid = ciab->ciatodmid;
    ULONG low = ciab->ciatodlow;	// latch deactivated

    return ((hi << 8 | mid) << 8 | low) << 8;
}

    Display_Show();

    game.isPaused = FALSE;

    ULONG previousTime = GetCurrentTime();
    ULONG lag = 0;

    Game_UpdateDisplay();

    for (;;) {
        ULONG currentTime = GetCurrentTime();
        ULONG elapsedTime = currentTime - previousTime;
        ULONG fps = (256 * CLOCK_CONSTANT) / (227 * elapsedTime);
        previousTime = currentTime;
        lag += elapsedTime;

        ULONG ticks = 0;
        while (lag >= TIMER_INCREMENT_PER_SIMULATION_STEP) {
            Game_ProcessUserInput();
			
            if (game.exitRequested)
                break;

                Game_UpdateState();
                lag -= TIMER_INCREMENT_PER_SIMULATION_STEP;
                ticks++;
            }
		
            if (game.exitRequested)
                break;

            Game_UpdateDisplay();

            TinyText_MoveTo(80 - 8, 0);
            TinyText_PrintFormatted("%4ld fps", fps);

            TinyText_MoveTo(80 - 8, 1);
            TinyText_PrintFormatted("%4ld ipf", ticks);
    }

    game.isPaused = TRUE;

    PrintStatistics();

with this bit when I take over the system:

    ciab->ciacrb &= ~CIACRBF_ALARM;

[Thomas Richter]

Originally Posted by NovaCoder

I need a fast way to tack how much time has passed in my main loop.

Is that on Amiga or on *ix? On *ix, you have the clock function (as stated) with various clocks offering different resolutions. You also have gettimeofday() which has milliseconds precision which is in most cases precise enough. On Amiga, you have the ReadEClock() function of the timer.device (see its autodocs), which offers milliseconds resolution, though is not very precise over a very long time.



No, I do not recommend accessing the hardware. Reading the E-clock has certain quirks the Os takes care of.