Subject: [xsl] Re: RE: Re: XSLT and parallel processing From: Dimitre Novatchev <dnovatchev@xxxxxxxxx> Date: Wed, 26 Sep 2001 21:25:55 -0700 (PDT) |
> > Hello developers, is there a single XSLT processor that will > > make use of a > > multiprocessor platform in executing a transformation? > > I think if there were, we'd know about it. > > The design challenge, of course, is making sure that the synchronisation > overheads don't swamp the gains. A common experience with parallel execution > is that only 30% of the run time turns out to be parallelisable - for > example, it's hard to see how you could do the XML parsing, tree building, > and result tree serialisation in parallel. I think the above statistic is from attempts to parallelize imperative style programs -- not functional style ones. It is obvious that in the former synchronisation problems will prevail. What we're talking about is to perform in parallel the "sequential" flow of the transformation, e.g.: <xsl:apply-templates select="$nodeset1"/> <xsl:apply-templates select="$nodeset2"/> <xsl:apply-templates select="$nodeset3"/> or <xsl:call-template name="someDvCqtemplate"> <xsl:with-param name="theNodeSet" select="$half1"/> </xsl:call-template> <xsl:call-template name="someDvCqtemplate"> <xsl:with-param name="theNodeSet" select="$half2"/> </xsl:call-template> etc... In nontrivial transformations the time to perform such parts of a transformation (essentially all content-producers) may be 50%, 80% or even higher of the total time to perform the transformation. A simple example (only to illustrate my point!) is reversing a 1MB string using a "divide and conquer" algorithm. It must be obvious, that much more than 30% of the time is parallelizable in this case. (It is obvious that nothing will be gained in "parallelization" of a head-then tail recursive algorithm.) And the majority of simple recursive algorithms have their "divide and conquer" counterparts. Exploiting parallelism will make "practical" transformations that take prohibitively long time if handled sequentially, thus increasing the power and usefulness of XSLT applications. Cheers, Dimitre Novatchev. __________________________________________________ Do You Yahoo!? Get email alerts & NEW webcam video instant messaging with Yahoo! Messenger. http://im.yahoo.com XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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