Hi,
Am Mittwoch, 21. Juni 2006 18:31 schrieb Bill Woessner:
> Hi. I just downloaded and am playing with LAPACK++. I apologize for
> emailing you directly. According to the project page, the mailing
> lists are down.
Are down? They shouldn't be - where did you read this?
> I'm looking at the web page
>
> http://lapackpp.sourceforge.net/html/laslv_8h.html
>
> And I have a question. I can use the function LUFactorizeIP to
> compute the LU factorization of a matrix (presumably by calling
> DGETRF). But how do I then use the factorization to solve the system
> with a given right hand side?
This particular function obviously cannot do this. Currently there is no C++
function available, but:
> The LAPACK routine I want to call is DGETRS. I searched for it in the
> source base. It appears in fmd.h and gfd.h. But neither of those
> files appear in the documentation.
The header files are the correct location. You need to look into the header
files directly, then you will see in gfd.h that I added a comment that says
this code is neither tested nor verified and might very well be broken. The
explanation for this is as follows: I never needed the LU factorization all
the time since I took over lapack++, so that part was never reviewed and
verified by me. What I *did* need was a QR factorization, and that's why the
class LaGenQRFactComplex exists. I just never came around to add a similar
class for the LU decomposition.
Hm... looking at fmd.h, it seems to me this header file might actually work.
If you already know DGETRF and DGETRS, then you will find exactly these two
functions in the fmd.h header file. If I recall correctly, then this is even
mentioned in that very old "LAPACK++ User's Manual " as mentioned on
http://lapackpp.sourceforge.net/html/index.html
> Alternatively, I can use the function LaLUInverseIP to explicitly
> compute the inverse. But that's almost never a good idea.
Right. I didn't like this InverseIP function as well -- maybe I should add
such a comment to that.
> Can you point me in the right direction, here?
Yea, look into the LAPACK++ User's Manual, use the functions from the fmd.h
header which will use a class from the gfd.h header but you don't have to
care about that class, apart from passing it to the function.
Christian
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