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Topic: MAT file takes forever to save with big object array
Replies: 6   Last Post: Dec 6, 2012 2:34 PM

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Posts: 1,187
Registered: 4/16/10
Re: MAT file takes forever to save with big object array
Posted: Dec 21, 2010 12:48 PM
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"Alexey" wrote in message <iepsb9$mrm$1@fred.mathworks.com>...
> Hi,
> I have a 65k-element array of objects of a particular class.

> >> whos results
> Name Size Bytes Class Attributes
> results 1x65000 3025921848 StrategyResultDef
> When I try to save it to a MAT file I get the following error:

> >save backtesting/files/technical-obj
> Warning: Variable 'results' cannot be saved to a MAT-file whose version is older
> than 7.3.
> To save this variable, use the -v7.3 switch.
> Skipping...
> And the variable 'results' is not saved.
> If I do:

> >save -v7.3 backtesting/files/technical-obj
> I do not get an error but it takes about 4 hours to save the file and its size is 1.5gb.
> I want to save the results for later processing but at this rate it's easier for me to re-generate the results every time.
> I will have a look at reducing the size of the structure but does anyone have any suggestions as to what is the best way to save the results like this?
> Kind Regards,
> Alexey

Hmm that does seem like a really long time. I frequently save/load 9GB files (structs with 3-3GB fields) and it usually takes a few minutes (MAC r2009b, 64bit). I have found for simple computations it's quicker to recalculate than to save. I.e: write a script that loads/generates what you need, run it, go get a coffee.

You could also try writing it to a binary file using fwrite and reading it in with fread. This is a pain though since you need to remember: dimensions, classes, bytes to skip if necessary etc.

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