From: Jeff Strickrott <jstric01@cs...>  20030509 19:39:23

Hello All: I am new to the vxl environment and I am trying to port code that was written to use the NAG numerical library and/or a subset of LAPACK and need to have the following LAPACK/CLAPACK or NAG routines:  DSYEV  compute all eigenvalues and, optionally, eigenvectors of a real symmetric matrix A.  DGETRF  compute an LU factorization of a general MbyN matrix A using partial pivoting with row interchanges.  DGETRI  compute the inverse of a matrix using the LU factorization computed by DGETRF.  DGEEV  compute for an NbyN real nonsymmetric matrix A, the eigenvalues and, optionally, the left and/or right eigenvectors. I believe that your vnl_real_eigensystem will do the same thing.  F04AEF: calculates the accurate solution of a set of real linear equations with multiple righthand sides using an LU factorization with partial pivoting, and iterative refinement. That is given a set of real linear equations AX = B , the routine first computes an LU factorization of A with partial pivoting, PA =LU , where P is a permutation matrix, L is lower triangular and U is unit upper triangular. An approximation to X is found by forward and backward substitution. The residual matrix R =B  AX is then calculated using additional precision, and a correction D to X is found by solving LUD = PR . X is replaced by X + D and this iterative refinement of the solution is repeated until full machine accuracy has been obtained. My expertise is not with computer vision or numerical routines (yet :) ) and I have the following questions: 1. Would it be easier to just obtain CLAPACK and use the appropriate routines from there? Has anyone compiled both CLAPACK and vnl together? 2. Add the FORTRAN routines per the procedures in the appendix? 3. What are (if any) the thread safety issues with vxl, and in particular the vnl libraries? 4. Any idea for a source for the F04AEF routine? 5. Any other suggestions? Thanks in advance for the help. Regards Jeff Strickrott Multimedia Database Laboratory Dept. of Computer Science Florida International University Miami, FL 