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vhong
Joined: 19 Jan 2006
Posts: 1
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 Posted: Thu Jan 19, 2006 4:20 pm Post subject: Timing |
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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! |
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jimparis
Joined: 10 Jun 2005
Posts: 1179
Location: Boston
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| Posted: Thu Jan 19, 2006 5:07 pm Post subject: Re: Timing |
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| vhong wrote: | | 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.
| Quote: | | 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. |
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urchin
Joined: 02 Jun 2005
Posts: 121
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| Posted: Thu Jan 19, 2006 7:06 pm Post subject: |
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| sceKernelLibcGettimeofday() definitely gives microseconds. |
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chp
Joined: 23 Jun 2004
Posts: 313
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| Posted: Thu Jan 19, 2006 7:23 pm Post subject: |
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I've more recently started using the realtime clock. This gives you a fixed high-frequency timer and should be very reliable.
Example:
| Code: |
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
}
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PeterM
Joined: 31 Dec 2005
Posts: 125
Location: Edinburgh, UK
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| Posted: Sat Jan 21, 2006 3:58 am Post subject: |
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| chp wrote: | | 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. |
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TyRaNiD
Joined: 18 Jan 2004
Posts: 918
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| Posted: Sat Jan 21, 2006 4:18 am Post subject: |
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| 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. |
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PeterM
Joined: 31 Dec 2005
Posts: 125
Location: Edinburgh, UK
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| Posted: Sat Jan 21, 2006 4:25 am Post subject: |
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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! |
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chp
Joined: 23 Jun 2004
Posts: 313
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| Posted: Sun Jan 22, 2006 7:21 am Post subject: |
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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. :)
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PeterM
Joined: 31 Dec 2005
Posts: 125
Location: Edinburgh, UK
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| Posted: Sun Jan 22, 2006 8:03 am Post subject: |
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| Yep I must have done something very silly - I'll go back and recheck. |
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