Re: Hash table performance
On Sun, 22 Nov 2009, Marcin Rze?nicki wrote:
On 21 Lis, 20:44, Tom Anderson <t...@urchin.earth.li> wrote:
On Sat, 21 Nov 2009, Marcin Rze?nicki wrote:
On 21 Lis, 19:33, Jon Harrop <j...@ffconsultancy.com> wrote:
I'm having trouble getting Java's hash tables to run as fast as .NET's.
Specifically, the following program is 32x slower than the equivalent
on .NET:
You are using Hashtable instead of HashMap - probably the performance
loss you've observed is due to synchronization (though "fat"
synchronization might be optimized away in case of single thread you
still pay the price, though lower).
I'd be *very* surprised if that was true. In this simple program,
escape analysis could eliminate the locking entirely - and current
versions of JDK 1.6 do escape analysis.
First of all, escape analysis is turned off by default.
Curses! I knew it was experimental when it first came into 1.6, but i
thought it was mature and on by default in the latest version.
The next thing is that there is subtle difference between synchronized
method and synchronized block. Hashtable has the former - escape
analysis does not help here very much afaik.
Could you explain why? I don't see why they should be any different. You
can rewrite:
synchronized void foo() {
// ...
}
As:
void foo() {
synchronized (this) {
// ...
}
}
With exactly the same semantics, no?
tom
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