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Thanks TJ. I've been playing around with code all morning and I'm now
starting to understand the implications of this for chart redraw speed.
I have found this confusing. For example, I have some quite complex
code that only requires 100 previous bars. As such it excutes nice and
fast because it doesn't use a lot of history. However, if I then drag
onto that chart, some ostensibly very simple 'daily pivot' calcualtion
code that requires the use of TimeFrameGetPrice() three times, then
the number of bars required jumps up to 15,000 odd for the reasons you
have outlined. Suddenly the whole chart becomes completely unusably
slow since it is now having to calculate 15,000 bars on ALL code on
the chart I assume?? So simple code added to complex code on a chart
can create a huge calculation overhead?
As an aside, I assume you can only make one call to Setbarsrequired()
per chart...? What happens if you drag and drop a number of indicators
onto one chart that each have their own settings of Setbarsrequired()...?
Many Thanks for clearing this up for me.
--- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko" <groups@xxx> wrote:
>
> As written here:
> http://www.amibroker.com/kb/2008/07/03/quickafl/
> and illustrated here:
> http://www.amibroker.com/gifs/barindex_small.gif
>
> BarCount is in direct relation with bar requirements.
> BarCount is actually number of bars visible PLUS calculated
requirements.
>
> > They require 5,000 bars each. Again, why?
> Again as written here:
> http://www.amibroker.com/kb/2008/07/03/quickafl/
> every function has internally known requirements.
> QuickAFL does not really care about "exact" requirements.
> It just needs to have some safe estimate. With safe
> it means that too much is good, too few is not.
> For some functions with dynamic requirements, some kind
> of assumption is being made. For those functions it is 5000.
> Read however the "IMPORTANT NOTES" part of the document
> mentioned already many times.
>
> The difference between in-funciton or out, is very simple.
> If you don't actually CALL the function, it does not add to
> the requirements. The definition does not matter.
> What is important is actual CALL.
> If you call multiple times - the requirements add up.
> Again, this is all really described in detail in the docs
> http://www.amibroker.com/kb/2008/07/03/quickafl/
>
> Note that my documents are condensed and each sentence
> is usually packed with important info, so slow reading is advised.
>
> Best regards,
> Tomasz Janeczko
> amibroker.com
> ----- Original Message -----
> From: "sidhartha70" <sidhartha70@xxx>
> To: <amibroker@xxxxxxxxxxxxxxx>
> Sent: Saturday, September 20, 2008 1:48 AM
> Subject: [amibroker] Re: Confusing Behaviour...!!!
>
>
> > Tj thanks.
> >
> > But I just want to get this 100% clear so I don't have to come back to
> > this again.
> >
> > On exactly the same chart... same settings, same zoom etc... One line
> > of code requires 5,000 previous bars within a function structure, and
> > outside of a function structure it requires 500. Why? It makes no
> > difference if I move around the chart, or zoom the chart etc. The
> > number of pervious bars required doesn't seem dynamic. It's very much
> > fixed.
> >
> > In the case of the following lines,
> >
> > H1=SelectedValue(TimeFrameGetPrice( "H", inDaily, -1 ));
> > L1=SelectedValue(TimeFrameGetPrice( "L", inDaily, -1 ));
> > C1=SelectedValue(TimeFrameGetPrice( "C", inDaily, -1 ));
> >
> > They require 5,000 bars each. Again, why? Sorry to be thick here, and
> > I'm sure it's blindingly obvious to you... But I don't see how
> > BarCount has anything to do with these two examples...??
> >
> > Thanks Again for taking the time.
> >
> > --- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko" <groups@> wrote:
> >>
> >> BarCount is DYNAMIC, it may change with every execution.
> >> You should not think about it as a constant.
> >> It can change with zoom factor, tooltip display (uses less),
> >> interpretation, selected bar, etc, etc.
> >>
> >> Also first execution after applying indicator always uses
> >> all bars, only subsequent runs use less.
> >>
> >> Best regards,
> >> Tomasz Janeczko
> >> amibroker.com
> >> ----- Original Message -----
> >> From: "sidhartha70" <sidhartha70@>
> >> To: <amibroker@xxxxxxxxxxxxxxx>
> >> Sent: Saturday, September 20, 2008 1:15 AM
> >> Subject: [amibroker] Re: Confusing Behaviour...!!!
> >>
> >>
> >> > Thanks TJ. I do know about Quick AFL and I have read that document
> >> > throughly before.
> >> >
> >> > But I can't see how it applies in this case with these specific
> >> > examples. And I definately can't see the difference between one
being
> >> > inside a function or not.
> >> >
> >> > Can you explain?
> >> >
> >> > TIA
> >> >
> >> > --- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko" <groups@>
wrote:
> >> >>
> >> >> Please read this:
> >> >>
> >> >> http://www.amibroker.com/kb/2008/07/03/quickafl/
> >> >>
> >> >> Best regards,
> >> >> Tomasz Janeczko
> >> >> amibroker.com
> >> >> ----- Original Message -----
> >> >> From: "sidhartha70" <sidhartha70@>
> >> >> To: <amibroker@xxxxxxxxxxxxxxx>
> >> >> Sent: Saturday, September 20, 2008 12:50 AM
> >> >> Subject: [amibroker] Confusing Behaviour...!!!
> >> >>
> >> >>
> >> >> > Hi,
> >> >> >
> >> >> > I'm trying to get some code to run as fast as possible. As such
> > I've
> >> >> > been studying the 'Display Chart Timing' option under
> >> > preferences>misc.
> >> >> >
> >> >> > I've noticed some behaviour that I can't explain. I hope others
> > may be
> >> >> > able to.
> >> >> >
> >> >> > Firstly I notice that when my chart requires 10,000+ bars I
> > start to
> >> >> > notice latency in AmiBroker, despite running a very fast PC. I
> > assume
> >> >> > that is normal at that number of bars...?
> >> >> >
> >> >> > So here's the problem...
> >> >> >
> >> >> > Under normal circumstances my code requires 297 previous bars.
> >> >> >
> >> >> > However, If I add the following lines, the number of
previous bars
> >> >> > required increases by 5,000 for each instance. So after
these three
> >> >> > lines of code I am now needing 15,297 pervious bars.
> >> >> >
> >> >> > H1=SelectedValue(TimeFrameGetPrice( "H", inDaily, -1 ));
> >> >> > L1=SelectedValue(TimeFrameGetPrice( "L", inDaily, -1 ));
> >> >> > C1=SelectedValue(TimeFrameGetPrice( "C", inDaily, -1 ));
> >> >> >
> >> >> > Even stranger, when I add the following line of code into
the main
> >> >> > body of code,
> >> >> >
> >> >> > test=((BarCount - 1) - LastValue(TroughBars(L, 0.05,10)));
> >> >> >
> >> >> > It adds 500 bars to my previous bars required (total new 797).
> >> >> >
> >> >> > However if I call a function and simply return the following,
> >> >> >
> >> >> > return ((BarCount - 1) - LastValue(TroughBars(L, 0.05,10)));
> >> >> >
> >> >> > It now requires 5,000 previous bars instead of the 500 outside
> > of the
> >> >> > function (total now 5,297).
> >> >> >
> >> >> > Can anyone explain this behaviour...?
> >> >> >
> >> >> > Many Thanks
> >> >> >
> >> >> >
> >> >> >
> >> >> >
> >> >> > ------------------------------------
> >> >> >
> >> >> > Please note that this group is for discussion between users
only.
> >> >> >
> >> >> > To get support from AmiBroker please send an e-mail directly to
> >> >> > SUPPORT {at} amibroker.com
> >> >> >
> >> >> > For NEW RELEASE ANNOUNCEMENTS and other news always check
DEVLOG:
> >> >> > http://www.amibroker.com/devlog/
> >> >> >
> >> >> > For other support material please check also:
> >> >> > http://www.amibroker.com/support.html
> >> >> > Yahoo! Groups Links
> >> >> >
> >> >> >
> >> >> >
> >> >>
> >> >
> >> >
> >> >
> >> > ------------------------------------
> >> >
> >> > Please note that this group is for discussion between users only.
> >> >
> >> > To get support from AmiBroker please send an e-mail directly to
> >> > SUPPORT {at} amibroker.com
> >> >
> >> > For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
> >> > http://www.amibroker.com/devlog/
> >> >
> >> > For other support material please check also:
> >> > http://www.amibroker.com/support.html
> >> > Yahoo! Groups Links
> >> >
> >> >
> >> >
> >>
> >
> >
> >
> > ------------------------------------
> >
> > Please note that this group is for discussion between users only.
> >
> > To get support from AmiBroker please send an e-mail directly to
> > SUPPORT {at} amibroker.com
> >
> > For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
> > http://www.amibroker.com/devlog/
> >
> > For other support material please check also:
> > http://www.amibroker.com/support.html
> > Yahoo! Groups Links
> >
> >
> >
>
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