Re: improved QR & Cholesky updating

[John W. Eaton]

On 21-Jan-2009, Jaroslav Hajek wrote:

| Not really missing. What I meant is that after I fix this issue,
| without qrupdate the functions will be present but sub-optimal. Maybe
| some code will want to detect the situation. Now that I think of it,
| how does "testif" detect that HAVE_QRUPDATE has been defined? Can this
| be done directly from an m-file? If yes, then the above last argument
| is dead...

It's a bit of a kluge:

  if (isempty (findstr (octave_config_info ("DEFS"), __feat{1}{1})))

For "testif HAVE_QRUPDATE", __feat{1}{1} would be HAVE_QRUPDATE.

If you think this would be a useful thing to be able to check for
generally, then I think we should have a separate function for this,
and maybe make it work more reliably than just using findstr on the
value returned by octave_config_info ("DEFS").

I can see where some feature checks like this might be useful, but I
still think it would be best to avoid having very many checks of this
kind in the Octave sources if possible.

| OK. I originally considered rebasing QR & CHOL classes on a common
| templated ancestor, but eventually I realized there was really not
| that much code to share, as most methods are relatively thin wrappers
| for the Fortran ones.
| Still I can write a .cc file containing the replacement templates and
| use that even in the current code.

OK.

Thanks,

jwe