reordering does not work for ICC?

[Barry Smith]

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
>