Re: Make sparse automatic mutation to dense matrices optional

[David Bateman]

John W. Eaton wrote:
> 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.
> 

Yeah, there were already some complaints, though I prefer it to be true.
Ok, I checked it in as off by default.

D.