Here's what I'm seeing. I have a 5000 bar database, of minute bars. I open a chart and an AFL that does one thing:
_TRACE("test" );
I don't use printf, I don't know what difference there is between it and TRACE, but anyway.
I set the chart interval to hours, which reduces the number of chart bars to a small number. But my test trace still prints 200 times.
Why is it printing 200 times for a chart with ~83 bars in it? I have even set barsrequired prior and forward to 0, and it still prints 200 times.
And as far as chart refresh events, does clearing the trace window count? Because if I clear the trace window, it reprints everything 200 times again.
I also should say again I have my refresh to 0, so no chart refresh should occur unless I:
a) load the chart the first time
b) move the scroll bar in the chart
c) a new bar is created because the chart is live
In the end AB is very different from other backtesting apps. Where you have a series of bars, and your code is fired once for every bar, no matter how often you scroll back and forth. If you paint the chart, whatever you painted is attached in memory to the chart and if you scroll outside of that view, it dissapears, but the event handler for that bar is never fired again when you scroll it back into view.
This is what's driving me batty because I expected it to be just like that.
--- In amibroker@xxxxxxxxx ps.com, "sidhartha70" <sidhartha70@ ...> wrote:
>
> Conrad... your code, for example Printf("Test" ); will execute every time the AFL executes, and that is done on each chart refresh... for each chart.
>
> Effectively a chart refresh 'event' causes your AFL to execute.
> That's why you get many 'test's in the trace window.
> Now, if you have a 5,000 bar DB, AFL will only execute over the bars it needs to which is either defined by the user using SetBarsRequired( ) or by AB automatically. This reduced number of bars that are refreshed is called 'quick AFL'.
>
> --- In amibroker@xxxxxxxxx ps.com, "Conrad Joach" <consolejoker@ > wrote:
> >
> > Agree, I'm not fully grasping the catalysts.
> >
> > Frankly I'm more of a fan of an event driven system. You override events, and you can look at the time series from any event, and each event is obviously fired once per bar.
> >
> > This just has my head spinning, and I've been coding for a decade and a half. It just doesn't feel natural to me and the lack of clarity on the behavior of the trace window is making it very hard for me to debug.
> >
> > If I print out the word "test", why does it show up 200 times on a 5000 bar chart? Can anyone answer this?
> >
> > --- In amibroker@xxxxxxxxx ps.com, Snoopy <snoopy.pa30@ > wrote:
> > >
> > > Conrad,
> > >
> > > I am a newbie as well, so I might be way off base, and expect more
> > > experienced folks to set us straight...
> > >
> > > I think you (and I) have not fully grasped the ARRAY Processing
> > > methodology of AFL.
> > >
> > > Try thinking of it as if you are using Excel - and you paste a formula
> > > into an entire ROW.
> > > When you finish the paste, it does the calculation.
> > >
> > > You (and I) need to better understand what triggers the running of the
> > > AFL (I assume a new data bar will trigger it - not sure when - start, or
> > > complete).
> > >
> > > And for your benefit, you could also use the afl functions for First
> > > Visible Bar and Last Visible Bar.
> > >
> > > I hope this helps.
> > >
> > > Snoopy
> > >
> > > Conrad Joach wrote:
> > > >
> > > > I'm just not understanding the way AB is evaluating AFL for a chart.
> > > > Let me break it down.
> > > >
> > > > Let's say I have a database with 100 1 minute bars, 100 minutes of quotes.
> > > >
> > > > Now let's say I have a chart, and that chart is very narrow and only
> > > > shows 10 bars worth of data.
> > > >
> > > > I write an AFL sript. I want to do a very simple thing.
> > > >
> > > > For every bar in the series of 100, I want to check if it's visible
> > > > (meaning it's inside the 10 bar window that is viewable in the chart),
> > > > I want to print the date and time of that bar. For this example let's
> > > > say the chart is positioned at the end, showing bar 91-100.
> > > >
> > > > The script should send the date and time of bars 91-100 to the trace
> > > > window. As far as I'm concerned there should only be *10* lines in the
> > > > trace window, no more, no less. I guess this means setting the forward
> > > > bar padding to 0, and the prior bars to 0.
> > > >
> > > > But here's the catch. These 100 bars are history. As soon as its
> > > > loaded, bar 101 comes in across the wire. The script should only run
> > > > *once* for bar 101.
> > > >
> > > > This is the paradigm I'm used to seeing in almost every other
> > > > backtesting system. I don't want my AFL script to run 10 times for
> > > > bars 92-101 when that 101st bar crosses the wire. I just want the last
> > > > bar evaluated, and the ability to look back at prior bars.
> > > >
> > > > Where am I going wrong? Many thanks for any help you can provide.
> > > >
> > > >
> > >
> >
>