Hi,
Sorry, I made a stupid/obvious mistake - (unsigned-byte 32) instead of some kind of floating-point number :P It would be nice to have an error message though..
Thanks for gsll, it's been pretty useful so far.
On Fri, Jun 19, 2009 at 12:54 AM, Nimalan Mahendrannimalan.mahendran@gmail.com wrote:
Hello everyone,
I'm trying to see whether I could use SBCL (or whatever CL implementation) as an alternative for Matlab in machine learning research. I have gsll running, but I saw that gsll's SVD, (sv-decomposition u s v) is converging to the wrong answers for the identity matrix.
M = [1 0 0; 0 1 0; 0 0 1]
but Matlab's SVD works fine.
Here's what happens in gsll/SBCL:
(setf M1 (MAKE-MARRAY '(UNSIGNED-BYTE 32) :INITIAL-CONTENTS '((1 0 0) (0 1 0) (0 0 1)))) (setf u (copy m1)) (setf s (make-marray 'vector-unsigned-byte-32 :dimensions 3)) (setf v (make-marray 'matrix-unsigned-byte-32 :dimensions '(3 3))) (sv-decomposition u s v)
GSL> u #<MATRIX-UNSIGNED-BYTE-32 #2A((0 0 0) (2147483648 0 3220176896) (0 2147483648 0))> GSL> s #<VECTOR-UNSIGNED-BYTE-32 #(268809831 296241371 268543215)> GSL> v #<MATRIX-UNSIGNED-BYTE-32 #2A((2083159301 2991920483 0) (2147483648 0 1072693248) (0 3220176896 0))> GSL>
The answers are definitely not right.. I don't think the right memory addresses are even being accessed.
I noticed in the definition of SV-decomposition in svd.lisp, the :outputs parameter is (A S V), but according to the GSL documentation at http://www.gnu.org/software/gsl/manual/html_node/Singular-Value-Decompositio..., maybe it should be (A V S)? I'm not sure how these parameters to defmfun actually work or what they mean (although I am familiar with cffi..). I was getting the same numbers even when I did SVD on this matrix:
M = [1 0 0; 0 2 0; 0 0 3]
so a memory access error seems likely to me.
Would someone mind helping me fix this?
Thanks!
Nimalan Mahendran