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Blitz Devel : |
From: David Weber (weber_at_[hidden])
Date: 1998-08-14 02:02:03
Hi
> > banded matrices that gets its bandwidth at runtime. That seems
> > to be easier in blitz++ than in sl++ since blitz++ matrices
> > get a structure *object* on construction, whereas sl++ matrices
> > inherit the structure class and there seems to be no constructor
> > that could initialize this base class with suitable data.
>
> Sounds reasonable. You can probably use Array<T,2> to store
> the data. I'd suggest using the mapping
>
> Band Mat Array<T,2>
> (i,j) -> (i,j-i+L)
>
> where L is the lower bandwidth (not known at compile time),
> and the array is of size N x (1+L+H) where H is the upper
> bandwidth. This requires a bit of wasted space in the Array,
> but makes indexing much simpler (and therefore efficient).
A shot in the dark here. LAPACK uses specific storage conventions for banded matrices and it would be very convenient if Blitz++ was able to store special matrices in the same format as LAPACK.
The LAPACK special matrix representation docs are available at http://www.netlib.org/lapack/lug/node110.html and the manual is available at
http://www.netlib.org/lapack/lug/lapack_lug.html
--Dave W.
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Prof. David Weber, Dept. Elec. Eng., University of Stellenbosch,
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Home phone : +27 21 852 4623 Email : weber_at_[hidden]
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