[Numpy-discussion] Calling LAPACK function dbdsqr()?

Philip Semanchuk philip@semanchuk....
Thu Dec 13 14:40:34 CST 2012


On Dec 13, 2012, at 2:47 PM, Charles R Harris wrote:

> On Thu, Dec 13, 2012 at 12:26 PM, Philip Semanchuk <philip@semanchuk.com>wrote:
> 
>> Hi all,
>> I'm porting some Fortran code that makes use of a number of BLAS and
>> LAPACK functions, including dbdsqr(). I've found all of the functions I
>> need via scipy.linalg.lapack.get_lapack_funcs/get_blas_funcs() except for
>> dbdsqr().
>> 
>> I see that the numpy source code (I looked at numpy-1.6.0b2) contains
>> dbdsqr() in numpy/linalg/dlapack_lite.c, but grep can't find that string in
>> the binary distribution on my Mac nor on Linux. If it's buried in a numpy
>> binary somewhere, I'm comfortable with using ctypes to call it, but I
>> suspect it isn't.
>> 
>> Can anyone point me to a cross-platform (OS X, Linux & Windows) way I can
>> call this function?
>> 
>> I'm unfortunately quite naïve about the math in the code I'm porting, so
>> I'm porting the code blindly -- if you ask me what problem I'm trying to
>> solve with dbdsqr(), I won't be able to explain.
>> 
>> 
> Not all the functions in lapack_lite are exposed in numpy. You might want
> to post on the scipy list, there have been recent additions supporting more
> lapack functions.

Thanks, I'll check scipy.

In numpy, I can see that lapack_litemodule.c is the layer that exposes select lapack functions via the Python interface, and dbdsqr isn't present in that file which is why I figured I would have to use ctypes to call it. I just can't figure out why dbdsqr appears in the source code but neither grep nor nm find any reference to it in the compiled binary.

Cheers
Philip






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