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RE: Different results of java and C verion of same program ?
- From: David Balazic <david dot balazic at hermes dot si>
- To: Mark Wielaard <mark at klomp dot org>, David Balažic <david dot balazic at hermes dot si>
- Cc: java at gcc dot gnu dot org
- Date: Fri, 10 Mar 2006 16:33:52 +0100
- Subject: RE: Different results of java and C verion of same program ?
From: Mark Wielaard [mailto:mark@klomp.org]
>
> On Wed, 2006-03-08 at 11:06 +0100, David Balažic wrote:
> > The main part of the program is a double loop, comparing
> each element of
> > a Vector
> > with all other elements of the Vector (except itself).
> >
> > Any ideas for speedup ?
>
> A Vector is synchronized on all operations. If you don't need this try
> using an ArrayList and loop over it with an Iterator. gcj might not
> optimize away the synchronized accesses on Vector.
I use a Vector, becasue I fill it with data read from file and I don't know
beforehand the amount of data.
Should copy the data over to new ArrayList, after the Vector is done ?
Unrelated to gcj :
I implemented a better algorithm, which is O(n) instead of O(n*n)
and compared Sun JIT to a C++ port. The C++ version is twice slower :-)
Regards,
David