On Mar 18, 2009, at 6:05 PM, James Maxwell wrote:
I've got a really frustrating, and really silly problem.
I have some fairly complex machine learning code I'm working on.
I've noticed inconsistent output from a particular method. I'm doing
some fairly nasty array and matrix stuff, which is all done in C,
and I pass the arrays around wrapped in NSData objects. What's
really strange is that, in this particular method, if I place an
NSLog after calling and unwrapping a particular 2D matrix, then the
output is as expected. If I remove the NSLog, the output is
incorrect (or at least, unexpected). The system is pretty complex,
and involves 4 different classes, so I won't post it here, and
obviously I don't expect any magical help. But does anybody have any
experience with something this flaky? Whereby literally adding a
single NSLog (and thus obviously slowing things down a fair bit)
makes the method run correctly?... It's just bizarre, to me.
Maybe somebody here has worked their way into a similar corner?
Obviously I've done something stupid somewhere, but I don't really
know how to go about finding it. It was weird enough to realize that
the NSLog could make or break my output - tracking down the actual
reason why is just baffling... Everything being done in these
classes is basically procedural stuff, so it doesn't seem like
timing should dramatically influence the output. But I am doing
*lots* of iterations over this data. Does that suggest anything?
Any thoughts very much appreciated.
NSLog() uses synchronization to ensure that logs gets written
atomically even if the output is longer than PIPE_BUF. If you are
calling NSLog() from multiple threads, you could be inadvertently
using synchronization primitives.
Cheers,
M
_______________________________________________
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
