Hello all, A while back I was interested in being able to do pivoting qr decomposition. I noticed that Chris Nix submitted a patch, but he indicated that he had more work to do (testing and filling in functionality). In the discussion around this, Luc suggested that I look at the QR decomposition in Levenberg-Marquardt. I did just that a few days ago. The code was very clear and nicely written (kudos to Luc). So, I copied the routine and made a new PivotingQRDecomposition class. The class is intended as a "drop in replacement" for QRDecomposition. I also copied the QRSolverTest and QRDecompositionTest. With the exception of testUnderdetermined in the solver test and testAEqualQR in QRDecompositionTest, the tests are unchanged (and all pass!). With testUndertermined, the "zeroed" rows of the solution matrix are interspersed throughout the matrix (because of pivoting). So I change the test to count all the rows that have zero norms, and check that it is the correct number. In testAEqualQR, I added a multiplication by the permutation matrix.
What is the best way to proceed? I don't want to trounce the additions that Chris made, but it looks like Chris has more sophisticated classes in mind. I don't see this proposed change competing with his. Does it make sense to bring back QRDecomposition interface (sorry Sebastien)? We can then keep both implementations until we are satisfied the pivoting one works. Thoughts? -Greg
