[SciPy-User] use of solveh_banded

Warren Weckesser warren.weckesser@enthought....
Fri Jul 9 11:54:26 CDT 2010


Giacomo Boffi wrote:
> i'm trying to use solveh_banded, but to no avail until now
>   


There was a bug in solveh_banded; see 
http://projects.scipy.org/scipy/ticket/676

It has been fixed for the soon-to-be-officially-released SciPy 0.8.

Warren


> from ipython -p scipy:
> ========================================================================
> In [74]: b
> Out[74]: array([ 1.,  2.,  3.,  4.,  5.,  6.,  7.,  8.,  9.])
>
> In [75]: m
> Out[75]: 
> array([[-1.,  3.],
>        [-1.,  3.],
>        [-1.,  3.],
>        [-1.,  3.],
>        [-1.,  3.],
>        [-1.,  3.],
>        [-1.,  3.],
>        [-1.,  3.],
>        [-1.,  3.]])
>
> In [76]: solveh_banded(m,b)
> ---------------------------------------------------------------------------
> ValueError                                Traceback (most recent call last)
>
> /home/boffi/<ipython console> in <module>()
>
> /usr/lib/python2.6/dist-packages/scipy/linalg/basic.pyc in solveh_banded(ab, b, overwrite_ab, overwrite_b, lower)
>     254                     lower=lower,
>     255                     overwrite_ab=overwrite_ab,
> --> 256                     overwrite_b=overwrite_b)
>     257     if info==0:
>     258         return c, x
>
> ValueError: On entry to DPBSV parameter number 8 had an illegal value
>
> In [77]: pbsv??
> Type:           fortran
> String Form:    <fortran object at 0xb60d5680>
> Namespace:      Interactive
> Docstring [source file open failed]:
>     dpbsv - Function signature:
>       c,x,info = dpbsv(ab,b,[lower,ldab,overwrite_ab,overwrite_b])
>     Required arguments:
>       ab : input rank-2 array('d') with bounds (ldab,n)
>       b : input rank-2 array('d') with bounds (nrhs,ldb)
>     Optional arguments:
>       lower := 0 input int
>       overwrite_ab := 0 input int
>       ldab := shape(ab,0) input int
>       overwrite_b := 0 input int
>     Return objects:
>       c : rank-2 array('d') with bounds (ldab,n) and ab storage
>       x : rank-2 array('d') with bounds (nrhs,ldb) and b storage
>       info : int
>
>
> In [78]:
> ========================================================================
>
> in particular, i cannot understand the "parameter number 8 had an
> illegal value" error message
>
> thank you in advance,
>                                                                 gb
>
>   



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