Speed Traps
Speed Traps
- Subject: Speed Traps
- From: John Nairn <email@hidden>
- Date: Wed, 14 May 2003 16:07:31 -0600
I spent a day rewriting a custom expression parcer for what I hoped
would give me much more speed but the final result is now slower. It is
hard to believe it is slower; could I be missing some Cocoa speed traps?
First version parced a NSString expression and evaluated as it went.
New version tokenizes the expression on the first past and then all
subsequent passes do no parcing, but just evaluate using the tokens.
The new version evaluation with tokens is slower than the first version
that parced AND evaluated on every pass. It does not make sense and I
am hoping I missed something or am using some Cocoa feature in new
version that is cause speed hang up?
One finding and maybe clue to speed traps:
In evaluating from tokens for expressions with groupings, I recursive
pass sub arrays of tokens to a function. If I allocate the sub arrays
and release them it it is slower than using autoreleased arrays. In
other words
subExpr=[[NSMutableArray alloc] initWithArray:...]
evaluate
[subExpr release];
is noticeably slower than
subExpr=[NSMutableArray arrayWithArray:...]
evaluate
I used the former method because I was concerned this large calculation
would be building up a large pool of autoreleased objects (several
hundred thousand) and slowing things down. I guess that was wrong.
------------
John Nairn (1-801-581-3413, FAX: 1-801-581-4816)
Web page:
http://www.mse.utah.edu/~nairn
_______________________________________________
cocoa-dev mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/cocoa-dev
Do not post admin requests to the list. They will be ignored.