benchmark result

Thu Dec 9 13:18:00 GMT 2004

On Mon, 2004年12月06日 at 13:56 +0000, Andrew Haley wrote:
> We could improve the performance of these collection classes with
> little work. What is required is someone to study the code, do some
> profiling, and fix things.

Ok, I did a bit of that. I used the attached trivial benchmark with
500000 iterations. On my pentium4, with 
"/opt/gcc-4.0.0/bin/gcj -gdwarf-2 -O3 -mtune=pentium4
MainArrayBench.java --main=MainArrayBench -o bench"
I reliably get:
[mlacage@chronos home]$ time -p ./bench 5000000
sum: 1642668640
real 2.62
user 2.30
sys 0.22
Then, I modified slightly ArrayList to include its own implementation of
Iterator which accesses the data member directly without doing through
the ArrayList getter but which does all the checking implemented in
AbstractList.Iterator (basically, copy/paste AbstractList.Iterator and
replace get(pos++) with data[pos++]. A sample of that is also attached
to this email). I reliably got:
[mlacage@chronos home]$ time -p ./bench 5000000
sum: 1642668640
real 2.53
user 2.16
sys 0.24
I doubt you could get much better results and keep the specified
semantics of the iterators. Well, it should be possible to inline the
iterator methods directly in the iterator caller but that would involve
knowledge of the iterator implementation in the iterator clients which
is something I cannot imagine possible in the current gcc codebase.
Maybe the linker could help... 
Mathieu
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