Re: reordering does not work for ICC?

[Barry Smith <bsmith@xxxxxxxxxxx>]

   There is no mechanism to release that extra memory. Thus it is  
important to preallocate
well for large problems.

   Barry
On Nov 6, 2007, at 9:29 AM, Zhifeng Sheng wrote:

> Barry Smith wrote:
>
> > On Nov 6, 2007, at 3:29 AM, Zhifeng Sheng wrote:
> >
> > > Dear all
> > >
> > > I tried to reorder my the preconditioner with different reordering  
> > > schema.
> > >
> > > All worked well for ILU, but does not make any difference on ICC.  
> > > It seems that the reordering schema does not work for ICC at all....
> > >
> > > Is it supposed to be like this?
> >
> >
> > Yes, with sbaij only the upper triangular part of the matrix is  
> > stored; hence reordering doesn't make sense
> > since the values needed in the reordered form are not available.  
> > You can use the SeqAIJ format if you want
> > to do reorderings with the ICC.
> >
> > Barry
> >
> > > PS: I have a symmetric matrix and I would like to save some  
> > > memory. I used SBAIJ with block=1, but some told me it's not  
> > > efficient ...
> >
> >
> > SBAIJ with block=1 is just as efficient as AIJ! The is seperate  
> > code for each block size.
> >
> > Barry
> >
> > > So... what can I do to save some memory on matrix and  
> > > preconditioner?
> > >
> > >
> > > Thank you
> > > Best regards
> > > Zhifeng Sheng
> Thank you for your answer.
>
> Could you please tell me if I can first assemble the matrix with a  
> sufficiently large nonzero number per row and then release the  
> redundent memory after the assembly is done?
>
> and what does MatCompress do? I tried it on my matrix, nothing  
> happened ...
>
> Thank you
> Best regards