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Hi Thomas,
> Tomasz wrote in the "Data And PlugIn Speed" thread
>I may add that the concept of independent rendering from multiple threads
>although attractive from first look, it inevitably hits the wall of GDI
>which in all current versions of Windows has
> single system-wide exclusive global lock, which means that only ONE thread
> can actually render at one time. This means that adding threads does not
> give you better performance.
>The truth is that all current releases of Windows are not particularly
>suited for multi-core/multi-CPU
>but good news is that Microsoft apparently have given these limitations
>some thought and
>many of them are removed in Windows 7.
That is true for rendering only! (Apps main thread is allowed to write the
GDI device. So rendering is limited to a single thread.)
But indicator calculation (and trading logic) could get executed by any
threads. Am I right? So doing the calculation on a background thread than
doing chart painting with the "main" thread would increase processor usage
and increase chart refresh reate? (I guess we all have dual and quad core
CPUs...)
How about separating "calculation refresh rate" and "chart refresh rate"? So
I could request my panel to execute 3 times per sec without chart repaint
(this could be executed by any threads) and refresh visible chart in every
3rd sec (this requires rendering, so calculation is done by a background
thread, and painting is done by main thread))?
Any thoughts?
Regards,
Y
(I know it is not doable in a day work, but I guess all short
term/daytraders are having trouble bacause of refresh limitations.)
--------------------------------------------------
From: "Julian" <juliangoodsell@xxxxxxxxxxxx>
Sent: Sunday, July 12, 2009 8:14 PM
To: <amibroker@xxxxxxxxxxxxxxx>
Subject: [amibroker] Per Chart Refresh Rates
> Hi Tomasz, I thought I'd start a new thread on this topic as I think it's
> an interesting one.
>
> Tomasz wrote in the "Data And PlugIn Speed" thread
>> I may add that the concept of independent rendering from multiple threads
>> although attractive from first look, it inevitably hits the wall of GDI
>> which in all current versions of Windows has
> single system-wide exclusive global lock, which means that only ONE thread
> can actually render at one time. This means that adding threads does not
> give you better performance.
>
> In response to that Tomasz,
> you're referring to performance on the basis of multiple charts being
> rendered per refresh update.
> E.g. If you have ten charts on screen, and they take a total of 2 seconds
> to render, then there's little performance gain to be had by threading
> them because of the GDI lock. That is fine and I get that.
>
> But what I'm referring to is the ability to control which charts render
> when, so that all ten don't have to be updated every refresh.
> The problem is that in real time mode with the refresh interval set to 0
> in the preferences, if I have a tick chart that only takes 10ms to update,
> it's still only going to be rendered every 2 seconds because that's how
> long the other nine charts take to render, even though I don't need them
> to be updated multiple times per second, but maybe only once every 5
> seconds or even every minute.
>
> If we could set refresh rates per chart, then you could have time critical
> tick charts update as fast as possible, and longer timeframe or more time
> expensive/less critical charts only update every 5 seconds or even longer.
>
> By staggering chart updates, traders would have much greater control over
> performance and not waste so much processing power updating charts that
> don't need to be. This would trounce any other kind of performance
> improvement that could be gained by optimizing the rendering engine
> itself, and would require no threading or any real change to the current
> architecture that I can see.
>
> Moreover, it appears this functionality is already in AB, but just that
> there's no way for the user to control it.
> The requestTimedRefresh() function enables you to update only the chart it
> is applied to, so they can obviously be rendered independently of each
> other.
>
> The problem though is that it is not enforceable. If I specify a refresh
> interval of 1 in the preferences, and then requestTimedRefresh(10) on a
> chart, that chart still gets updated every second along with all the
> others, and then once more after ten seconds.
>
> Giving the option to make requestTimedRefresh() enforceable would be one
> way of enabling this functionality. Perhaps add an enforceable parameter
> to the function like:
> requestTimedRefresh(10, onlyvisible=True, enforceable=false).
> Then if I specify requestTimedRefresh(10, true, true), that chart should
> only update every 10 seconds, irrespective of what I've set in the
> preferences.
>
> Would this be as easy to implement as I think it is? If so, I think the
> benefits would be rather large.
>
> Jules.
>
>
>
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