Jens Axel Søgaard writes: > See my post in this thread 3 days ago. It is attached.
It isn't, but I found it in the thread, thanks! I am mostly interested in using it as an example for the Racket FFI, given that I know LAPACK rather well. > > Transposition can be avoided in many practically relevant situations > > (e.g. symmetric matrices), so such decisions should be taken on a > > case-by-case basis. > > The problem is that (Matrix Flonum) and LAPACK has different > representation for matrices. In order to take a (Matrix Flonum) > and turn it into a LAPACK one, the entries in the underlying vector > must be transposed. That depends. If as I assume (Matrix Flonum) used C-style row-major order, then transposition *may* be necessary. In some cases it's sufficient to tweak the parameters fed to LAPACK a bit. For example, if you work with symmetric matrices, you just claim your lower-triangular matrix to be upper-triangular and everything works fine. > If we(I) had realized it sooner, the representation in (Matrix Flonum) > would have been the same. I am not sure it's a good idea to design a matrix library around LAPACK. There are also nice C and C++ libraries, which in general use row-major order. Konrad. ____________________ Racket Users list: http://lists.racket-lang.org/users
