Re: [xml] xmllint --postvalid much slower than --valid [PATCH]

[Daniel Veillard <veillard redhat com>]

On Tue, Feb 24, 2004 at 10:18:51AM +0100, Petr Pajas wrote:
> On Monday 23 February 2004 11:08, Daniel Veillard wrote:
> >   Can you bugzilla this ? BTW, only --valid really mean DTD validation in
> > the sense of the definition in the XML REC. Also I think I did make my
> > patch when testing with your data when using --dtdvalid (as your files were
> > not having a DOCTYPE, if I remember correctly --postvalid would not work).
>
> That's true, but I do have DOCTYPE in the production files, so that's not it.  
> The same difference appears even with --dtdvalid and --postvalid.
>
> >   yes. best is to relink statically for profiling with gprof. Please
> > double check you're really using the new shared libraries and if problem
> > persists, then bugzilla.
>
> Thanks for the hint on gprof. That allowed me to identify and fix the problem 
> (patch attached). The real problem actually is related to what I reported 
> before. xmlAddRef uses xmlHash/xmlList combination to store IDREFs 
> attributes. The problem is that both xmlListInsert and xmlListAppend work 
> with ordered lists (they search for first lower/higher element in the list 
> before inserting/appending). Unless a comparing function is given, the 
> default one, xmlListCompare, is used. This function compares data as numbers. 
> In our case the data are strucutures, so their pointer addresses are 
> compared. So with --valid/--dtdvalid, xmlListAppend seems to be quicker (as 
> the pointers grow) while with --postvalid it may/may not be otherwise  
> (because almost all memory is already allocated so the pointer values don't 
> necessarily grow). But in fact, there is no need for any ordering at all, so 
> it is quite sufficient to pass the list constructor a dummy comparison 
> function which always returns 0 (elements are equal). Then 
> xmlListAppend/xmlListInsert may be used equally  (no real difference).
> That's what my patch does. All tests pass with it, so it should be safe to 
> apply, but you may want to check the naming and placing of xmlDummyCompare.

  Right, the analysis and the patch looks correct, applied, I can see the
speedup :-)

   thanks a lot !

Daniel

-- 
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