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[xsl] Re: XSLT and parallel processing (Was: RE: XSL-List Digest V3 #1125)
Subject: [xsl] Re: XSLT and parallel processing (Was: RE: XSL-List Digest V3 #1125)|
From: Dimitre Novatchev <dnovatchev@xxxxxxxxx>
Date: Thu, 27 Sep 2001 06:01:44 -0700 (PDT)
Colin Adams <AdamsC at kssg dot com> wrote:
[summary of previous discussion snipped]
> MK>I think if there were, we'd know about it.
> MK>The design challenge, of course, is making sure that the synchronisation
> MK>overheads don't swamp the gains. A common experience with parallel
> MK>is that only 30% of the run time turns out to be parallelisable - for
> MK>example, it's hard to see how you could do the XML parsing, tree
> MK>and result tree serialisation in parallel.
> DM>I think the above statistic is from attempts to parallelize imperative
> DM>programs -- not functional style ones. It is obvious that in the former
> DM>synchronisation problems will prevail.
> Of course, I will be using a pure functional language to write the processor
> - I think this will also be a
> quicker approach than trying to take existing source code (Saxon, for
> instance), and trying to parallize it.
> But first I have to make the XML parser that I have (HaXml) namespace aware.
The most direct way to go about it would be to re-use the source code of some
existing XSLT processor and modify only the stylesheet execution logic.
The modification that has to be done does not seem too complex:
For every member of a sequence S of (sibling) content-producing xsl instructions
(e.g. xsl:apply-templates) initiate its execution in a separate thread. When all
threads have completed, serialize their outputs based on their code position in the
I'm making the assumption here, that there is an underlying OS that will be able to
execute different threads on different processors.
Even if only the above is successful, this will be a significant achievement.
I think that in the future the most valuable xslt code (e.g. standard template
libraries or xslt applications that are executed most frequently) will be accessed
in a pre-compiled form, therefore the need to speed-up xml parsing and stylesheet
compilation will not be so great.
> OK, when I've actually got something written (I have yet to start), I'll ask
> you for some suitable test cases.
Hope this time will come soon! :o)
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