| Re: Memory de-allocation and "restore" [message #4300 is a reply to message #4160] |
Tue, 16 May 1995 00:00  |
thompson
Messages: 584
Registered: August 1991
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Senior Member |
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rutledge@zvezda.mit.edu (Bob Rutledge) writes:
> I apologize to those who are boring of this subject, but I
> have not received any answers at all, and I cannot believe that
> the difficulty I am having MUST exist -- there must be SOME way
> around it.
> I save a variabele "specdata" (a common variable) using a "save" command.
> "specdata" contains, at different times, different information, but all of the
> same structure, to various files.
> I ran the following test:
> for i=0L, n_ffiles-1 do begin ; CYCLE THROUGH THE FILES
> specdata = 0
> restore, filename=ffiles(i), /verbose
> endfor
> which cycles through files and restores to the variable "specdata". On the
> first iteration, the loop takes about 10 seconds, and no time is spent
> at the "specdata=0" line. On the second iteration, approximately 2minutes
> are required by the "specdata=0" line, and >10 minutes are required on
> that "restore". The second "restore" is half the memory size of the first
> "restore", so it is not a problem of the memory requirements.
> Is this REALLY the way IDL is? Is there REALLY no way to improve this
> (either for me to improve this, or RSI to improve this). If this cannot
> be improved, I cannot use IDL in the future, because it is simply not
> fast enough on silly 'ol I/O.
> Bob
I think that the reason why you didn't get any response is because such
behavior is not normal. Please give more information about your configuration:
What platform? What operating system? How much RAM memory do you have? How
large are the files you're trying to restore? If applicable, what quotas are
you allowed? How loaded down is your system with other processes and other
users?
It sounds like you're having a problem with memory fragmentation. This can
happen if the amount of data you're trying to read in is significant compared
to your total available memory (e.g. 30%). It's just like disk fragmentation.
The problem could be especially acute if your RAM memory is small and you're
mainly using virtual memory on disk. If your operating system is Microsoft
Windows, I've heard (but can't say for certain) that it is especially prone to
memory fragmentation problems.
Bill Thompson
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