| Re: Bug in STRMID system routine [message #82473] |
Thu, 13 December 2012 12:04 |
Heinz Stege
Messages: 189
Registered: January 2003
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Senior Member |
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Hi David.
On Thu, 13 Dec 2012 12:48:04 -0700, David Fanning wrote:
> The last example, though, completely and utterly locked up
> my machine. No Task Manager, no nothing, requiring a hard
> reboot and cost me about an hour's worth of work. Not too
> excited about that. :-(
>
Sorry for that. Here I get a simple error message, that IDL is unable
to allocate memory. I would have told, if there were serious problems.
Here is the complete output:
IDL> strmid_demo
% Compiled module: STRMID_DEMO.
Starting with:
heap memory used: 728889, max: 753748, gets: 1078, frees:
238
The string needs about 10485760 bytes:
heap memory used: 11214886, max: 53158085, gets: 1083, frees:
241
A small substring needs the same amount of memory as the original
string:
heap memory used: 21707071, max: 21707071, gets: 1087, frees:
242
The memory can be released by a simple operation:
heap memory used: 11221313, max: 21707082, gets: 1088, frees:
243
The following is slow, but works:
heap memory used: 11276405, max: 21762174, gets: 3090, frees:
1243
... and this probably runs into a memory allocation error (if you
don't have tons of RAM):
% Unable to allocate memory: to duplicate string.
Not enough space
% Execution halted at: STRMID_DEMO 29
F:\home\idl\comp.lang.idl-pvwave\strmid_demo.pro
% $MAIN$
IDL>
Cheers, Heinz
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| Re: Bug in STRMID system routine [message #82475 is a reply to message #82473] |
Thu, 13 December 2012 11:48  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Heinz Stege writes:
> strmid needs a bug fix. When I start with a very long string
> a=string(byte(randomu(seed,1024^2*10)*(127.-32.))+32b)
> and then extract a short substring
> b=strmid(a,1,2)
> the result b needs 10 MB of memory. As much as the original string a.
>
> This overhead of memory can be released by a statement like b=b[0] or
> b=b+''. However this is only a workaround and should be fixed in the
> system routine itself.
>
> A demo is attached below.
I ran the demo on a Windows 7 64-bit OS with IDL 8.2.1.
It appears the bug is fixed, because the example with
a small string took a small amount of memory, rather than
the large amount you report.
The last example, though, completely and utterly locked up
my machine. No Task Manager, no nothing, requiring a hard
reboot and cost me about an hour's worth of work. Not too
excited about that. :-(
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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