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Re: Reading columns of binary data [message #49678 is a reply to message #49596]

Tue, 08 August 2006 07:57

Foldy Lajos
Messages: 268
Registered: October 2001

Senior Member

On Mon, 7 Aug 2006, JD Smith wrote:

> I'd regard this as yet another example of why IDL needs a fast
> compiled "side-loop" primitive for generic looping operations which
> don't need the full conveniences of the interpreter loop (ability to
> hit Control-C to interrupt, etc.). I should be able to say:
>
> a=fltarr(500000,/NO_ZERO)
> f=0.0
> for_noblock i=0L,500000L-1L do begin
> point_lun,un,i*100L
> readu,un,f
> a[i]=f
> endfor
>
> and not have it be 100x slower than the equivalent in C.
>
> JD
>

Hi,

I mentioned assoc yesterday, so let's try again:

arr=assoc(un, [0.])
for i=0L,500000L-1L do a[i]=arr[25l*i]

it will do the point_lun/readu in one step, so it should be a little bit
faster. But I think a faster loop here would not help much, as disk I/O
is the limiting factor.

regards,
lajos

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[Message index]

		Re: Reading columns of binary data By: Wayne Landsman on Mon, 07 August 2006 15:21
		Re: Reading columns of binary data By: JD Smith on Mon, 07 August 2006 14:54
		Re: Reading columns of binary data By: Foldy Lajos on Mon, 07 August 2006 11:07
		Re: Reading columns of binary data By: news.verizon.net on Mon, 07 August 2006 10:41
		Re: Reading columns of binary data By: Foldy Lajos on Mon, 07 August 2006 10:30
		Re: Reading columns of binary data By: Foldy Lajos on Tue, 08 August 2006 07:57
		Re: Reading columns of binary data By: JD Smith on Mon, 07 August 2006 15:44

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