Re: sparse matrix newbie

From: Fernan Bolando (fernanbolando_at_mailc.net)
Date: 11/29/03 

Date: Sat, 29 Nov 2003 02:59:18 GMT

In article <20031127195139.29282.00001122@mb-m10.aol.com>, Dan Tex1 wrote:
>>From: Fernan Bolando fernanbolando@mailc.net
>>Date: 11/26/03 4:57 PM Pacific Standard Time
>>Message-id: <571987b260e99de5110a3b03355d618f@news.teranews.com>
>>
>>In article <20031123204144.18969.00000848@mb-m18.aol.com>, Dan Tex1 wrote:
>>>>From: Fernan Bolando fernanbolando@mailc.net
>>>>
>>>>In article <20031122155423.03434.00000745@mb-m29.aol.com>, Dan Tex1 wrote:
>>>>>>From: Fernan Bolando fernanbolando@mailc.net
>>
>>>>>>I am looking for a sparse matrix library for linux gcc compiler.
>>>>>
>>>>> Do you really "need" a sparse solver? The complexity of such a solver is
>>>>much
>>>>> higher than just a simple solver algorithm. Why not just write the
>>>>"solver"
>>>>> code yourself?
>>>>
>>>>I am also considering writing it myself, But it seems a sparse program
>>>>is very problem specific and indeed very complex. I am condering using
>>>>gsl as the matrix solver initially and update it to sparse matrix as the
>>>>need come up. Do you think this is an effective approach considering I
>>>>am new at this? So far I have tested my initial code using gsl dense
>>>>matrix code.
>>>
>>> That sounds like an effective and logical approach to me. Sparse codes
>>are
>>> great when you need them. They're just too complex for when you don't need
>>> them ( and aren't already set up to use them ). If a group of problems
>>aren't
>>> large enough, the effort required to set up sparse solvers just won't pay
>>off.
>>>
>>I am wondering which is faster? calculating a large matrix in dense
>>matrix algorithm or processing the matrix in sparse mat. Do you think it
>>is advantagous to initially analyze the matrix then decide whether to
>>solve it in dense or sparse? You see am thinking of putting both dense and
>>sparse matrix into my program and then write a simple code to
>>pre-analyse the problem and then decide whether to use sparse or dense
>>matrix.
>>
>>I am thinking that if a matrix does not have enough zero's then the
>>advantages of using sparse matrix disappears plus I would be wasting so
>>much cpu time processing the data into sparse.
>>
>>,Fernan
>
> I'd say you're thinking along the "right" lines. Keep in mind that it always
> depends on what types of systems you are doing the solving for. However,
> with a sparse solver... you'll need to arrange your input data in such a way
> as to facilitate your sparse solver. Thus... using a sparse solver will take
> more time even to prep your data to send to the solver. As a result... it may
> not be all that easy for you to set up your algorithm to work with both a
> sparse solver and a more elementary solver.
>
> If I were in your shoes... ( keep in mind I don't know what type of problems
> you are solving or how large they truly are 0... I'd write the algorithm to
> use a simpler solver. However... while writing it... I'd be aware of the
> fact that I might want to implement a sparse solver later. In other words...
> I'd attempt to write the code so that it can be easily altered later without
> causing too many headaches. An advantage to this way is that you will learn
> things along the way that you can make better ( ie. redo ) when you add
> sparse solver capabilites.
>

Ok thanks very much

,Fernan

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