[petsc-users] a cost question for sparse factorization

[Jed Brown]

On Sat, Apr 28, 2012 at 04:56, Umut Tabak <u.tabak at tudelft.nl> wrote:

> All you will get are asymptotics, not sharp operation counts. For 2D, the
>> bounds are O(n^{1.5} flops and O(n log n) space; for 3D they are O(n^2)
>> flops and O(n^{4/3}) space. This is covered in Alan George's book,
>> http://www.cse.illinois.edu/**courses/cs598mh/george_liu.pdf<http://www.cse.illinois.edu/courses/cs598mh/george_liu.pdf>
>>
>>  Dear Jed,
> I am not good at these cost computations, is 'n' the number of nonzeros in
> the matrices?


No, n is the number of degrees of freedom in the model.

There is no estimate just in terms of the number of nonzeros because
ultimately, the cost is limited by the size of minimal vertex separators.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120428/9cd68706/attachment-0001.htm>