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From Dario Laera <la...@cs.unibo.it>
Subject Re: Active node tree pruning in FOP trunk
Date Fri, 24 Oct 2008 15:34:00 GMT

Il giorno 24/ott/08, alle ore 00:52, Dario Laera ha scritto:

>> It is clear why long paragraphs make a difference. Why does one- or
>> two-column layout make a large difference? Simply due to the twice
>> larger number of pages? I do not understand the left-aligned case. Is
>> this not just the same as a first-fit layout?
>
> Nice questions... I'm trying to understand this behavior too, the  
> first time I've implemented the pruning on prototype was for another  
> reason and I accidentally noticed the performance boost :)
> About one or two columns, or better, long or short lines: again, I  
> don't know why, maybe it's just because the double number of breaks;  
> I thing I noted is that for the same number of active node with  
> shorter lines the gap between startLine and endLine is wider than  
> with long lines. I don't know if this is meaningful.

I managed to get some graphs and now I'm more convinced that line  
width matters. I've compared the file left-aligned, single block and  
single column with the analogous file in two columns but with nearly  
half of its words: in other words, they produce in the final layout  
nearly the same number of breaks. The pruning was deactivated.
You can see the graph attached (startLine and endLine refers to the  
left scale while activeNodeCount to the right scale): with the same  
number of knuth elements (x axis) the short lines data grows much  
faster than long lines data.

A really strange thing: is it theoretically possible that the amount  
of active nodes is greater than the number of knuth elements? As you  
can see in the graph, for short lines there are >14000 active nodes  
but only ~7000 knuth elements...


Dario


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