[SciPy-user] Possible bug in linalg.lu

[Nils Wagner]

Pietro Berkes schrieb:
> 
> even faster, if you don't need to permute the matrix:
> linalg.lu_factor(C)


BTW, how can I check the sign of \det(C)= \pm \det(U) ?

P,L,U,info = linalg.lu(C)

detA = \pm prod(diag(U))

Nils

Remarks:

\pm denotes plus minus...


\det(A) = \det(P) \det(L) \det(U) = \det(P) \det(U)


> 
> On Monday 14 July 2003 16:23, Pietro Berkes wrote:
> > the function linalg.lu seems to be defined for real matrices only. if you
> > want to use it for complex ones, the fastest solution is probably to write
> > a wrapper to the lapack function ZGETRF. it should work like in the real
> > case (cfr. linalg/src/lu.f).
> >
> > regards,
> > pietro.
> >
> > On Monday 14 July 2003 15:29, Nils Wagner wrote:
> > > Hi all,
> > >
> > > >>> C
> > >
> > > array([[ 3.003+0.j,  1.   +0.j,  0.   +0.j,  0.   +0.j],
> > >        [ 3.   +0.j,  3.003+0.j,  2.   +0.j,  0.   +0.j],
> > >        [ 0.   +0.j,  2.   +0.j,  3.003+0.j,  3.   +0.j],
> > >        [ 0.   +0.j,  0.   +0.j,  1.   +0.j,  2.   +0.j]])
> > >
> > > >>> linalg.lu(C)
> > >
> > > Traceback (most recent call last):
> > >   File "<stdin>", line 1, in ?
> > >   File "/usr/local/lib/python2.1/site-packages/scipy/linalg/decomp.py",
> > > line 238, in lu
> > >     p,l,u,info = flu(a1,permute_l=permute_l,overwrite_a = overwrite_a)
> > > TypeError: object of type 'None' is not callable
> > >
> > >
> > > For what reason ?
> > >
> > > Nils
> > >
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