Re: Make sparse automatic mutation to dense matrices optional

[John W. Eaton]

On 26-Nov-2007, David Bateman wrote:

| John W. Eaton wrote:
| > On 16-Nov-2007, David Bateman wrote:
| > 
| > | While looking at SeDuMi one issue I had was that much of the code
| > | assumes that once a matrix is sparse it will stay that way and it so
| > | SeDuMi just assumes that certain matrices are sparse in some of its
| > | internal mex functions. Octave's habit of converting sparse matrices to
| > | full ones if that saves space, plays havoc with this.
| > | 
| > | I therefore propose to include an internal variable Vsparse_auto_mutate
| > | that can be used to enable or disable this functionality and that the
| > | "-traditional" option turns this off as that is what matlab does.
| > 
| > I think this patch is OK, but maybe we should set sparse_auto_mutate
| > to false by default for compatibility.
| > 
| > jwe
| 
| 
| It is for matlab compatibility mode, but not in general. Do you want it
| to be off by default always?

It doesn't matter much to me, but looking at the rest of the options
implied by --traditional, the only one that is not cosmetic seems to
be

  bind_internal_variable ("default_save_options", "-mat-binary");

so maybe it would be best to have sparse_auto_mutate false by
default as it can change the behavior of valid Matlab code, so I think
having the default be compatible would eliminate some confusion for
Matlab users who don't expect sparse matrices to suddenly become
full.

jwe