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TJ,
Just to bring a close to this subject,
It is important to keep an eye on the number of previous bars required
by a chart ESPECIALLY where you have multiple calls to code within
functions, as this may end up using far more previous bars than are
actually required.
Would you say that's a correct statement?
TIA
--- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko" <groups@xxx> wrote:
>
> Hello,
>
> SetBarsRequired can be called any number of times.
> Any call, overwrites any previous bar requirements,
> so the last call is the one that matters.
> That also allows you to completely overwrite any internally
> calculated requirements - put SetBarsRequired at the end of the formula
> and you have full control.
>
> Best regards,
> Tomasz Janeczko
> amibroker.com
> ----- Original Message -----
> From: "sidhartha70" <sidhartha70@xxx>
> To: <amibroker@xxxxxxxxxxxxxxx>
> Sent: Saturday, September 20, 2008 11:51 AM
> Subject: [amibroker] Re: Confusing Behaviour...!!!
>
>
> > 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@> 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@>
> >> 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
> >> >
> >> >
> >> >
> >>
> >
> >
> >
> > ------------------------------------
> >
> > 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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