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b,
My suggestion is : you should not worry too much about slow down.
You can put all "_" symbols into "unused" group and you will
be able to quickly filter it out via "exclude" filter in AA window.
Doing so will ensure that "_" symbols' data are not accessed at all
(because data required to filter out symbols are already
available in broker.master) therefore you won't see any slowdown at all.
By the way: even if there are more than 1000 files in single folder
the slowdown refers only to "OpenFile" call (relating to 'finding' the
file in the directory). It does not affect the speed at which given
file is read (once opened). Therefore overall speed is not affected
that much and there is really no need to worry.
Best regards,
Tomasz Janeczko
amibroker.com
----- Original Message -----
From: "b519b" <b519b@xxxxxxxxx>
To: <amibroker@xxxxxxxxxxxxxxx>
Sent: Sunday, June 08, 2003 11:34 PM
Subject: [amibroker] AB data base structure and speed (for Tomasz)
> Tomasz,
>
> Thank for the quick reply. I now understand that there is a speed
> reduction if there are more than 1,000 tickers in a folder.
>
> One more question: is this always the case? Or, is the speed
> reduction no longer a problem once AB lists the tickers in the
> broker.master file?
>
> My situation is this: I want to have about 5,000 inactive stocks in
> the same database as active stocks, but may will have the same
> ticker sysbol as these get reused. One way to handle this is to give
> each inactive ticker a prefix (like, _IBM). This has the advantage
> that a simple sort will put all the inactives together for each of
> watchlist management. The byproduct is that all the 5,000 inactives
> will end up in the same AB data folder (eg, "_").
>
> The alternative is to use a suffix for inactives (eg, IBM_x).
> Sorting is not quite so easy with a suffix, but it is still possible
> to select out the inactives using AB's strright call in a scan. Of
> course, this approach will distribute the inactives among AB's 26
> regular data folders (A, B, C, etc).
>
> I am open to any advise you or others may have for managing
> inactives and actives in the same database.
>
> b
>
> --- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko" <amibroker@xxxx>
> wrote:
> > b,
> >
> > Generally speaking all Microsoft file systems (FAT, FAT32, NTFS)
> slow down
> > when there is more than 1000 files in single folder. Exact results
> depend
> > on hard disk, disk cache, RAM size, disk fragmentation, etc.
> > Loading database however does not require reading all files as
> AmiBroker
> > maintains broker.master file that contains all info that need to
> be loaded
> > at startup. Individual files are accessed only when needed (when
> quotes
> > must be read, for example during scan).
> >
> >
> > Best regards,
> > Tomasz Janeczko
> > amibroker.com
> > ----- Original Message -----
> > From: "b519b" <b519b@xxxx>
> > To: <amibroker@xxxxxxxxxxxxxxx>
> > Sent: Sunday, June 08, 2003 3:37 PM
> > Subject: [amibroker] AB data base structure and speed (perhaps
> only Thomasz can answer)
> >
> >
> > > Does it matter if one puts several thousand tickers into a
> single AB
> > > data folder. For example, if one makes all inactive stocks with
> a
> > > prefix like _IBM? That will put about 5,000 stocks into the "_"
> > > folder in the AB database.
> > >
> > > Does having 5,000 or more tickers in the same folder slow AB
> down
> > > when retriving data?
> > >
> > > b
> > >
> > >
> > >
> > >
> > > Send BUG REPORTS to bugs@xxxx
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> > >
> > >
> > >
>
>
>
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