Hi Jeremias,
I'm getting better and better. I actually understood all parts of your mail. 
:-) So for ordinary users, the change is not very much in terms of performance 
gain, but better than nothing. For me, who will read information from the AT in 
my multi-pass solution to the "duplicate cell content problem" it doesn't make 
any difference either, since both IF and the AT-xml I see are generated from 
the same AreaTreeModel. Right?

Georg Datterl
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-----Ursprüngliche Nachricht-----
Von: Jeremias Maerki [mailto:d...@jeremias-maerki.ch] 
Gesendet: Mittwoch, 18. Februar 2009 10:30
An: fop-dev@xmlgraphics.apache.org
Betreff: Re: AW: Issues for after the IF branch merge

Hi Georg

On 18.02.2009 10:13:21 Georg Datterl wrote:
> Hi Jeremias,
> > I've also made performance measurements as part of this effort which 
> > highlights why it was done in the first place:
> > http://people.apache.org/~jeremias/fop/benchmark-2009-02-13/
> I'm probably missing something important here, but regarding the first graph:
> Isn't "direct" what ordinary users of fop do? Take a fo-file and then render 
> it? 


> Isn't "direct-via-if" what ordinary users of fop will do in the future, if IF 
> is the default? 


> Isn't the work done in "direct-via-if" the sum of the work done in "to-if" 
> and "from-if"? 

No. "to-if" renders the FO and uses IFSerializer (called by IFRenderer) to 
write an intermediate file. "from-if" parses the intermediate file (using 
IFParser) and generates a series of calls against an IFDocumentHandler and 
IFPainter implementation. So:

"direct-via-if" = "to-if" + "from-if" - serializing IF - parsing IF or "to-if" 
+ "from-if" = "direct-via-if" + serializing IF + parsing IF

The main motivation for the new IF is the fact that "serializing AT XML"
and especially "parsing AT XML" is very costly.

See also http://people.apache.org/~jeremias/fop/renderer-design-new.png
which shows the two different paths.

> And, if all the above answers are yes, why is the performance gain 
> noticed in "from-if" not more obviously related to the performance 
> gain in "direct-via-if"?

There was a "no" above so this is not applicable anymore. I hope I could clear 
up the gap.

Jeremias Maerki

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