reordering does not work for ICC?

[Zhifeng Sheng]

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