RE: Different results of java and C verion of same program ?

[Andrew Haley <aph at redhat dot com>]

David Balazic writes:
 > From: Mark Wielaard [mailto:mark@klomp.org] 
 > > 
 > > On Wed, 2006-03-08 at 11:06 +0100, David Bala¾ic 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 ?

No.  Simply replace all cases of ArrayList in your code with Vector.

 > 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 :-)

Err, something weird is happening.

Andrew.