| Re: Strange memory consumption? [message #13155] |
Fri, 16 October 1998 00:00 |
Alex Schuster
Messages: 124
Registered: February 1997
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Senior Member |
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Kevin Ivory wrote:
> Alex Schuster wrote:
>> I just noticed this:
>>
>> IDL> a = bindgen( 1000, 1000, 10 )
>> IDL> help, /mem
>> heap memory used: 10183855, max: 10183883, gets: 188,
>> frees: 61
>> IDL> a[*] = 1b
>> IDL> help, /mem
>> heap memory used: 10183906, max: 50183966, gets: 192,
>> frees: 63
>
> Hi Alex,
>
> I wasn't aware of that, but I would do it differently in the first place.
> If you know you want to initialize an array with a constant, there are
> much better ways of doing so. First of all, use bytarr instead of
> bindgen. Then you only have to add the constant you need:
>
> a = bytarr(1000, 1000, 10) + 1b
Oh, sorry I didn't make ths clear. Of course you are right, but my code
was intended as some example only in order to demonstrate the effect.
But it occurs several times in my program that I have a huge array and
have to re-initialize it to zero. I didn't expect that creating the
array again would be faster than using arr[*]=0, and that this costs
that much memory.
> There is another way of defining and inititializing an array in one step:
>
> a = make_array(1000, 1000, 10, value=1b)
>
> Initializing such large arrays, you might want to check the time
> consumption: On my system (Pentium 200 MHz, IDL 5.1.1 Linux, 64 MB RAM)
> the first assignment takes roughly 0.8s, the second takes 1.9s.
> (Your code takes 2 minutes! - probably because of swapping to hard disk)
Here it's around 0.3s vs. 1.7s, on an UltraSparc with enough memory.
Alex
--
Alex Schuster Wonko@weird.cologne.de PGP Key available
alex@pet.mpin-koeln.mpg.de
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| Re: Strange memory consumption? [message #13156 is a reply to message #13155] |
Fri, 16 October 1998 00:00  |
Kevin Ivory
Messages: 71
Registered: January 1997
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Member |
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Alex Schuster wrote:
> I just noticed this:
>
> IDL> a = bindgen( 1000, 1000, 10 )
> IDL> help, /mem
> heap memory used: 10183855, max: 10183883, gets: 188,
> frees: 61
> IDL> a[*] = 1b
> IDL> help, /mem
> heap memory used: 10183906, max: 50183966, gets: 192,
> frees: 63
Hi Alex,
I wasn't aware of that, but I would do it differently in the first place.
If you know you want to initialize an array with a constant, there are
much better ways of doing so. First of all, use bytarr instead of
bindgen. Then you only have to add the constant you need:
a = bytarr(1000, 1000, 10) + 1b
IDL> help, /mem
heap memory used: 10171230, max: 10171254, gets: 151, frees: 30
There is another way of defining and inititializing an array in one step:
a = make_array(1000, 1000, 10, value=1b)
Initializing such large arrays, you might want to check the time
consumption: On my system (Pentium 200 MHz, IDL 5.1.1 Linux, 64 MB RAM)
the first assignment takes roughly 0.8s, the second takes 1.9s.
(Your code takes 2 minutes! - probably because of swapping to hard disk)
Hope this helps
Kevin
--
Kevin Ivory Tel: +49 5556 979 434
Max-Planck-Institut fuer Aeronomie Fax: +49 5556 979 240
Max-Planck-Str. 2 mailto:Kevin.Ivory@linmpi.mpg.de
D-37191 Katlenburg-Lindau, GERMANY http://www.gwdg.de/~kivory2/
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