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<== Date ==> <== Thread ==>

Subject: Re: exporting waveforms
From: [email protected] (Pete Jemian)
To: [email protected]
Cc: [email protected]
Date: Tue, 7 Apr 98 10:11:55 CDT
The reason why et_wish is slow is because of the update mechanism
it uses to respond to CA monitors (the X event loop).  This says
nothing about the involvement or performance of BLT.  BLT was mentioned 
because it has support for "vectors" (which are used by et_wish to gather
waveforms from CA).  In the upgrade of BLT, the vector interface
was changed and nobody has yet updated et_wish to reflect these changes.
In the version of et_wish that I have, support for vectors was commented out.
Other EPICS-to-Tcl/Tk interfaces may exist, such as yours, which
have better performance than et_wish.  Maybe, with a little bit of work, 
et_wish can be improved with regards to update rate, as well as including
support for Tcl/Tk v8 and BLT v8 (when it becomes available).

Regards,
   Pete


Johannes van Zeijts wrote:
> 
> Pete Jemian wrote:
> > 
> > Do not advise using et_wish for this type of work.
> > Since BLT was upgraded ... is very slow when you have
> > a high update rate, such as with a strip chart or plotting
> > tool.
> > 
> 
> 
> I have used the BLT extension to tcl/tk with great success 
> (both for own use and
> in the control room). You ofcourse have to write the interface 
> code in C instead
> of only using tcl. After you do that correctly you can get as 
> fast live updates as
> StripTool or any other X11 plotting tool, with the same cpu usage. 
> There is
> definitely no inherent slowness to BLT, and as you note it gives 
> you a lot more
> flexibility than hardwired plotting code.
> 
> All my interface code at the moment runs through CDEV, but I can 
> show you the code
> if you are interested.
> 
> 	-Johannes
> 

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