[SciPy-User] use of solveh_banded

Giacomo Boffi giacomo.boffi@polimi...
Fri Jul 9 08:36:28 CDT 2010

```i'm trying to use solveh_banded, but to no avail until now
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