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Re: inverse gradient [message #64030 is a reply to message #63980]

Tue, 02 December 2008 07:45

pgrigis
Messages: 436
Registered: September 2007

Senior Member

erano wrote:
> On Dec 2, 4:45�pm, Paolo <pgri...@gmail.com> wrote:
>> erano wrote:
>>
>>>> Oddly enough, that's the second time sparse arrays have come up in one
>>>> week!
>>
>>>> You want LINBCG, which takes as input asparsematrix created using
>>>> SPRSIN. The help pages on them are pretty decent - give them a read.
>>
>>>> -Jeremy.
>>
>>> YES, we are at the right direction.
>>> BUT my matrix iz M*N (where M=2*N). when I add zeros to make it M*M,
>>> and thrn use the SPRSIN to make it sparse, the solution from LINBCG is
>>> noot good.
>>
>> How much is M and N?
>>
>> Paolo
>>
>>
>
> For the large array: N is between 10,000 to 800,000 and M=N*2.
> (actually, N is dim_x * dim_y of an image)

My suggestion is to operate on each line of the array
separately and loop over lines and columns.

This way you only need to deal with dim_x by dim_y
arrays, a much simpler problem...

Ciao,
Paolo

>
> Thanks again
>
> Eran

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[Message index]

		inverse gradient By: erano on Wed, 26 November 2008 02:10
		Re: inverse gradient By: pgrigis on Tue, 02 December 2008 10:59
		Re: inverse gradient By: erano on Tue, 02 December 2008 11:42
		Re: inverse gradient By: erano on Tue, 02 December 2008 10:50
		Re: inverse gradient By: pgrigis on Tue, 02 December 2008 09:20
		Re: inverse gradient By: erano on Tue, 02 December 2008 09:04
		Re: inverse gradient By: pgrigis on Tue, 02 December 2008 07:45
		Re: inverse gradient By: erano on Tue, 02 December 2008 07:12
		Re: inverse gradient By: pgrigis on Tue, 02 December 2008 06:45
		Re: inverse gradient By: erano on Tue, 02 December 2008 01:27
		Re: inverse gradient By: pgrigis on Fri, 28 November 2008 08:31
		Re: inverse gradient By: pgrigis on Fri, 28 November 2008 08:18
		Re: inverse gradient By: pgrigis on Fri, 28 November 2008 08:14
		Re: inverse gradient By: pgrigis on Fri, 28 November 2008 08:10
		Re: inverse gradient By: Jeremy Bailin on Fri, 28 November 2008 05:27
		Re: inverse gradient By: erano on Fri, 28 November 2008 01:31
		Re: inverse gradient By: Jeremy Bailin on Thu, 27 November 2008 06:24
		Re: inverse gradient By: pgrigis on Tue, 02 December 2008 14:44
		Re: inverse gradient By: erano on Tue, 09 December 2008 00:36
		Re: inverse gradient By: erano on Wed, 24 December 2008 01:55

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