which parameters define time slice duration in FreeRTOS, and how to calculate how long it will run one task before switching out that task and switching in another task.
I've found configTICK_RATE_HZ which sets number of ticks per second but how it relates to switch in and switch out in terms of tasks.
configTICK_RATE_HZ defines the timer tick frequency and thus the timeslice duration. With pre-emption enabled the set of tasks that have the highest priority and are ready to run (ie not blocked) will share the CPU with round-robin. On every tick interrupt a new task from that set will be scheduled.
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I have a NSTimer (running on main thread) that is supposed to go off every 0.02s. However, I notice that as memory usage start going up (the app captures a frame every tick and stores in an array) subsequent ticks begin to take more then 0.02s.
How can I solve this issue? I'm starting to think NSTimer is not suited for high-frequency tasks like this.
As the docs state,
A timer is not a real-time mechanism; it fires only when one of the
run loop modes to which the timer has been added is running and able
to check if the timer’s firing time has passed. Because of the various
input sources a typical run loop manages, the effective resolution of
the time interval for a timer is limited to on the order of 50-100
milliseconds.
Since 100 milliseconds = .1 seconds and your timer is supposed to run every 0.02 seconds, your timer schedule is far shorter than the timer's effective resolution and so you timer can easily get out of sync.
I want to determine necessary time to execute a procedure, time value must be returned in the first instruction in this procedure, like this:
procedure myProcedure;
begin
// determine necessary time here
//other instructions
end;
First, of all, is this possible? if yes, how can I do this?
Thanks for your replies
In general you cannot expect to do this. Unless you have carefully profiled the code on the machine on which you run it, under the exact conditions in which it runs. Without that information there's no way to reliably predict run time up front.
You actually want to display progress. Typically you do that by keeping track of how the overall task is progressing. If the task is made up of 50 similarly sized sub tasks, then you can measure proportion complete simply by knowing how many sub tasks are complete.
That's the normal way to measure progress for a progress bar. If you wish to estimate time to completion then make a note of when the task starts. Then, as worl proceeds, you can use simple maths to work out an estimate of the time remaining. If the first 10 sub tasks took 30 seconds, then estimate that the next 10 will take another 30 seconds.
I am trying to find out a way to increase the computation time of a function to 1 second without using the sleep function in xilinx microblaze, using the xilkernel.
Hence, may i know how many iterations do i need to do in a simple for loop to increase the computation time to 1 second?
You can't do this reliably and accurately. If you want do a bodge like this, you'll have to calibrate it yourself for your particular system as Microblaze is so configurable, there isn't one right answer. The bodgy way is:
Set up a GPIO peripheral, set one of the pins to '1', run a loop of 1000 iterations (make sure the compiler doesn't optimise it away!) set the pins to '0'. Hang a scope off that pin (you're doing work on embedded systems, you do have a scope, right?) and see how long it takes to run the loop.
But the right way to do it is to use a hardware timer peripheral. Even at a very simple level, you could clear the timer at the start of the function, then poll it at the end until it reaches whatever value corresponds to 1 second. This will still have some imperfections, but given that you haven't specified how close to 1 sec you need to be, it is probably adequate.
I have to display a timer in 10th second for a sport competition. I have do this using the OnTimer event of a TTimer. the interval is set to 100. My routine display the current min:sec.10th (ex.: 02:45.7 ) correctly but it seem that my timer loose about 4 second at each minutes if I comp. to normal clock.
There is a better way to get a time accuracy timer in Delphi XE2 (or XE3) ?
You can use a timer to display the current value of the clock, but use a different approach to calculate the elapsed time.
You have to know that Windows timers are not time accurate, and even if you set it to elapse every 100 milliseconds, it can take more to fire the OnTimer event and even it can miss some intervals if for some reason elapses two or more times before your application process it.
You can, for example, use the system high-resolution performance counter to track times with nano-second accuracy.
You can also use the Delphi TStopwatch class, which encapsulates the system calls and falls back to other method (GetTickCount) if the high resolution performance counter is not available in your machine.
Take also a look at the How to Accurately Measure Elapsed Time Using High-Resolution Performance Counter delphi.about.com article.
I am using Complex Event Processing (Esper) technology to provide a real-time candlestick calculations in my system. I am doing fine with calculating values, however I find it difficult to ensure that candle window starts at full minutes (for one minute candle) and ends before the next minute starts (i.e. candle 1[06:00.000 - 06:00.999], candle 2[06:01.000 - 06:01.999], etc... ).
Is there a pattern or command in Esper's query language that is able to provide such functionality?
I'd appreciate constructive comments and directions.
In Esper you can use a pattern to fire every minute at the zero second, i.e.
insert into TriggerEvent select * from pattern[pattern[every timer:interval(1 min).]
// named window to hold candle data, compute next candle
on TriggerEvent select * from NamedWindowCandle ....
// delete old data
on TriggerEvent delete from NamedWindowCandle
-rg
Local time is often different from exchange time, also there is latency in delivering tick data. Minute bars are often computed using exchange timestamp. The exchange timestamp value must be extracted from tick events. New minute bar event is sent when the tick timestamps enter new minute.