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Re: Sparse matrix problem
From: |
David Bateman |
Subject: |
Re: Sparse matrix problem |
Date: |
Wed, 03 Jan 2007 18:19:01 +0100 |
User-agent: |
Thunderbird 1.5.0.7 (X11/20060921) |
address@hidden wrote:
> > Ok, this was a lot more work than I though it would be, but here is the
> > patch. Basically it allows scalars to be stored in a sparse matrix
> > container and to be treated as if they were scalars. This is necessary
> > as Mathworks chose the path of letting the user store scalars as sparse
> > matrices rather than automatically reconverting these to scalars. In any
> > case the attached patch makes octave matlab compatible for scalars
> > stored as sparse matrices for all operators...
>
> But it does not solve the fact that (note element-wise division):
>
> [1+i 2-i] ./ [0 0-i]
>
> gives under Octave
>
> [NaN + NaNi 1 + 2i]
>
> and under Matlab
>
> [Inf + Infi 1.0000 + 2.0000i]
>
> Does it?
>
> Michael.
>
No as that is a problem with the underlying C++ complex class and not
octave at all.. Try the attached test program, which for me using g++
4.0.1 returns
(1+i) / (0 + 0i) : (nan,nan)
(1+i) / 0 : (nan,nan)
1 / 0 : inf
I have no idea if this is fixed in later versions of g++, but I hope
so.. As for MSVC, tell microsoft about their bug :-)
D.
--
David Bateman address@hidden
Motorola Labs - Paris +33 1 69 35 48 04 (Ph)
Parc Les Algorithmes, Commune de St Aubin +33 6 72 01 06 33 (Mob)
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#include <complex>
#include <iostream>
typedef std::complex<double> Complex;
int main (void)
{
std::cout << "(1+i) / (0 + 0i) : " << Complex(1.,1.) / Complex(0.,0.) << "\n";
std::cout << "(1+i) / 0 : " << Complex(1.,1.) / 0. << "\n";
std::cout << "1 / 0 : " << 1. / 0. << "\n";
return 0;
}
- Re: Sparse matrix problem, David Bateman, 2007/01/03
- Re: Sparse matrix problem, Michael Goffioul, 2007/01/03
- Re: Re: Sparse matrix problem, Dmitri A. Sergatskov, 2007/01/04
- Re: Sparse matrix problem, David Bateman, 2007/01/04
- Re: Re: Sparse matrix problem, John W. Eaton, 2007/01/04