Java performance (Saxon)

Slightly off-topic perhaps, for which I apologize, but I'm hoping someone
can help me shed some light on some Java performance figures. I've been
trying to make some performance improvements to Saxon, and have tested the
results using both Microsoft Java SDK and SUN JDK 1.2, both on the same Win
NT 4.0 box, with the following rather perplexing results (which are entirely
repeatable). There are 5 stylesheets A to E, with execution times as
follows, in seconds

                   A         B         C         D       E
Saxon 5.2, Sun     9.4       15.9      19.3      20.1    5.3
Saxon 5.2, MS      4.9        9.5      11.8      12.9   20.0
Saxon 5.3, Sun     7.3       12.3      18.4      18.0    5.8
Saxon 5.3, MS      3.1        5.2      19.0      10.8   19.8

All I can conclude from this is that there is a lot I don't know about the
different Java VMs! Stylesheet A is running twice as fast on MS as on Sun,
while Stylesheet E runs at barely a quarter of the speed. More worrying
still, my "improvements" have caused a very healthy speed-up of A and B, on
either VM, while on C they have made no difference on Sun but have made
things a lot worse on Microsoft.

I thought I'd share this, firstly to show the difficulty of doing any kind
of performance comparisons even with one XSLT processor let alone between
processors, and secondly in the hope that someone might be able to point me
in the direction of resources that will help me understand what's going on.
Any suggestions?

Mike Kay


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