On Fri, Dec 12, 2008 at 16:41, Shawn O. Pearce <spearce@xxxxxxxxxxx> wrote:
> If you'd like to send a patch to change it, I'll apply it. But I
> don't think its worth my time to make this toString() more efficient.
I mainly mentioned it because it's in a Class meant to be more optimal
than what Java ships with, but I agree with your reasoning that this
toString is not part of what needs to be optimized.
> Other areas of JGit I do try to micro-optimize, because they are
> right smack in the middle of the critical paths.
Hehe, I very much agree with not optimizing prematurely, and if you do
optimize to go for it all the way.
> E.g. look at ObjectId.equals(byte[],int,byte[],int). I hand-unrolled
> the memcmp loop because the JIT on x86 does *soooo* much better
> when the code is spelled out:
<code snipped>
Kind of sad that you have to write this kind of code if you want good
performance, ah well, perhaps someday... (import java.lang.optimized
;) ).
> This block is in the critical path for any tree diff code, in
> particular for a "git log -- a/" sort of operation. Its used
> to compare the SHA-1s from two different tree records to see if
> they differ. Not unrolling this was a huge penalty.
I reckon that is done a lot :). Ashame the JRE can't do that kind of
optimization for you. e.g., if you do:
for(int i = 0; i < constant; i++) {
some_code;
}
--
Cheers,
Sverre Rabbelier
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