Timing

[vhong]

Hello,

I've recently gotten into PSP development, and I'm totally loving it! I have one question which I have not been able to find any answers for.

From the examples and such I've seen, the only way to do timing is through sceKernelLibcTime, which returns seconds. Is there any way to retreive time in milliseconds?

I'd like to do some simple 2d animations properly, but I've been unable to find any examples/documentation on precise timing.

Thanks in advance!

[jimparis]

From the examples and such I've seen, the only way to do timing is through sceKernelLibcTime, which returns seconds. Is there any way to retreive time in milliseconds?

clock() and gettimeofday() should both give you microseconds.

I'd like to do some simple 2d animations properly, but I've been unable to find any examples/documentation on precise timing.

I'd recommend using SDL, there's plenty of documentation and example code on the net.

[urchin]

sceKernelLibcGettimeofday() definitely gives microseconds.

[chp]

I've more recently started using the realtime clock. This gives you a fixed high-frequency timer and should be very reliable.

Example:

Code: Select all

u64 last;
u32 tickFrequency = sceRtcGetTickResolution();
sceRtcGetCurrentTick(&last);

while (1)
{
 // get delta-time for current frame
 u64 curr;
 sceRtcGetCurrentTick(&curr);

 float deltaTime = (curr-last) / (float)tickFrequency;
 last = curr;

 // ... do whatever you want with the delta-time
}

[PeterM]

sceRtcGetCurrentTick()

I've no idea why, but when I tried using this function (before giving up and switching to clock()), it was taking a long time to finish (around .2 seconds per call!)

Perhaps I was doing something silly, but I'm pretty sure not.

[TyRaNiD]

Well the rtc stuff is probably sitting on an external bus so it perhaps needs to to query it. Maybe :P One thing you can possibly use is the profile registers though I don't think they are available when not running in kernel mode.

[PeterM]

It's no big deal now, since clock() works fine in Quake, but I assume that clock() probably just calls sceRtcGetCurrentTick() internally.

I must be doing something wrong there - I really didn't expect a high res timer query to take so long!

[chp]

I did a test of your claim, and I can safely say that it's false. :) Here's some info over the different methods used for timing and how often they can get called:

sceRtcGetCurrentTick() - around 511900 calls per second, or 1.953 microseconds per call.

gettimeofday() - around 120310 calls per second, or 8.311 microseconds per call.
4 times slower than using the RTC.

clock() - around 512500 calls per second, or 1.951 microseconds per call.
Actually slightly faster than the RTC, but I suspect this is because it returns a 32-bit value.

I don't know about you, but I'm sticking with the RTC timer mostly because it offers 64 bit values, and I like using native interfaces. Using gettimeofday() should be a big no-no if you want proper resolution. :)

[PeterM]

Yep I must have done something very silly - I'll go back and recheck.