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Re: Help Large_array [message #52617 is a reply to message #52616]

Tue, 20 February 2007 02:53

Paolo Grigis
Messages: 171
Registered: December 2003

Senior Member

wx_f@sohu.com wrote:
> w...@sohu.com wrote:
>
>>> I need to build a ut=dblarr(36000,500,25) in IDL's pro---sfit.pro.
>
>> It is not possible to build such an array with IDL 32 bit version,
>> no matter how much memory your system has.
>>
>> Ciao,
>> Paolo
>
> Mr Pallo
> Since ut=dblarr(20000,500,25) and ut=fltarr(36000,500,25)can be
> created by my PC(linux_IDL6.0),why it cannot do better(3.6 vs 2,double
> vs float)?
> a) What's the reason.Could you give a formula to explain
> quantitatively?

Take the number of elements in your array, call it n.

Take the size in byte of your data type (i.e. 4 for float,
8 for doubles etc.), call it m.

Then m*n is limited to 2^31.

As for the reason, we could speculate that IDL (32 bit) uses
long, signed integers internally to access the memory locations
where the elements of the array reside.

> b) What's the solution to the operation of large array once and for
> all(I mean by software not changing hardware)?

You'll be the one who has to find the best solution suited to
your problem, somehow you'll have to work with smaller chunks
of data.

Ciao,
Paolo

>
> thanks
> wxf
>
>
>

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[Message index]

		Re: Help Large_array By: JD Smith on Tue, 20 February 2007 09:27
		Re: Help Large_array By: Nigel Wade on Tue, 20 February 2007 04:15
		Re: Help Large_array By: Paolo Grigis on Tue, 20 February 2007 02:53
		Re: Help Large_array By: wx_f on Tue, 20 February 2007 01:44
		Re: Help Large_array By: Paolo Grigis on Tue, 20 February 2007 00:02
		Re: Help Large_array By: Brian Larsen on Mon, 19 February 2007 13:57
		Re: Help Large_array By: liamgumley on Tue, 27 March 2007 07:20

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