[Lapackpp-devel] Re: lapackpp and banded matrices (was: help lapackpp)

[Christian S. <sti...@tu...>]

Hi,

thanks for your feedback. In the future please write to the mailing list 
lapackpp-devel instead to individual developers.

Am Dienstag, 20. Dezember 2005 21:34 schrieb ll...@21...:
>   I am new to lapack++ and I found this package is very good. I have
> compared lapack++ with matlab in solving a 1000x1000 equaions and it
> turns out that lapack++ do a great job. Thanks for your contribution.

Nice to hear.

> However, I have some questions in using lapack++. I have a test code
> like
>
> LaGenMatDouble A(N,N);
> LaBandMatDouble B(N,2,2); // for five-diagonal matrix
> LaVectorDouble x(N), f(N);
>
> LaLinearSolve(A, x, f);
>
> The program shown above can be compiled without any problem. 

I have never used the banded matrices, so I cannot guarantee anything with 
them. You need to manually verify that the functions really do what they are 
supposed to do. I can only guarantee (or rather: try to guarantee) the 
correct functionality for the GenMat classes.

> I just 
> wonder if I really need lapack (not lapack++) installed. I have not
> linked the library of lapack and blas and the program can also be run
> and get the correct answer???

Well, if it works, then you can just be happy. I wouldn't bother as long as it 
works.

> I am using lapack++ 2.4.2, windows

If you're using the self-installing setup.exe file, then this comes with a DLL 
of blas and lapack, too.

> Another question is about band matrix, I try to build a five-diagonal
> matrix with LaBandMatDouble. In my case, building a band matrix with
> LaBandMatDouble is ok, but it seems that LaLinearSolve has no
> corresponding interface for solving LaBandMatDouble!? How can I solve a
> band matrix with lapack++?

As I said: the banded matrices have been untouched since the original 
lapack++-1.0. If you really need this functionality, then: 1. find out the 
original LAPACK function call that does what you want, 2. see whether there 
is already a declaration of that function call in include/lapackd.h, 3. if 
there is, then you're almost done: Go into src/linslv.cc and copy&paste the 
program code from one of the other functions, e.g. 
LaLULinearSolve(LaGenMatDouble& A, LaGenMatDouble& X, const LaGenMatDouble& 
B ), but replace the matrix types and the F77NAME function call with your 
appropriate names. Then add the declaration to the include/laslv.h header, 
compile and test your new function. If the tests behave as expected, send 
your program code to me and I'll happily add it to the library in CVS.

Christian