Re: problem encoding large float* matrix
Re: problem encoding large float* matrix
- Subject: Re: problem encoding large float* matrix
- From: James Maxwell <email@hidden>
- Date: Tue, 1 Dec 2009 11:57:44 -0800
Wow! I'd forgotten how helpful this list is - and how quickly!
Everyone pointing out my use of &coincidences is obviously right. I figured it out soon after getting my first reply. I already made an @property accessor for coincidences, so I just used that and the crashes went away.
As far as the NSData goes, I'm glad you pointed the redundancy of it out. I'll just encode the bytes themselves.
Just a note to Sherm that coincidences is malloced as (maxCoincs * inputSize * sizeof(float)), because it's a 2D float array with dimensions maxCoincs x inputSize.
The software is just a research project, for now, so no worries about portability (I'll cross that bridge if I ever get there!).
Now onto the crash that's happening when I try to actually *use* the app after loading from a saved file! ugh... ;-)
thanks all,
J.
On 2009-12-01, at 11:40 AM, Sherm Pendley wrote:
> On Tue, Dec 1, 2009 at 1:47 PM, James Maxwell
> <email@hidden> wrote:
>> I'm trying to save the state of my app. It chews up a lot of memory, most of which is in large float* matrices. I'm getting an EXC_BAD_ACCESS error in -encodeBytes:length:forKey: and I'm just wondering what might be happening. The float* "coincidences" is a malloced array.
>>
>> NSUInteger coincsSize = maxCoincs * inputSize * sizeof(float);
>
> This looks suspicious to me. Based on the variable names, it looks
> like you malloc(maxCoincs * sizeof(float)), then store the actual
> number of floats in the buffer in inputSize. If that's what you're
> doing, you only need to multiply by maxCoincs (to get the size of the
> whole buffer) or by inputSize (to find out how much of the buffer is
> actually in use) - not by both of them.
>
>> NSData* coincData = [NSData dataWithBytesNoCopy:&coincidences length:coincsSize];
>> [aCoder encodeBytes:[coincData bytes] length:coincsSize forKey:@"coincidences"];
>
> As someone else said, if you created the buffer with "coincidences =
> malloc(...)", then you don't need to dereference it here; doing so
> will give you the address of the pointer variable, not the address of
> the buffer to which it points.
>
> What's the point of creating the NSData object here? Wouldn't this be
> just as good?
>
> [aCoder encodeBytes:coincidences length:coincsSize forKey:@"coincidences"];
>
> sherm--
>
> --
> Cocoa programming in Perl:
> http://www.camelbones.org
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