[petsc-users] loading huge matrix with MatLoad in parallel implementation

[Yujie]

Thanks, Barry. I use X86_64 CPU, do I need to use "--with-64-bit-indices"?

Regards,
Yujie

On Thu, Jul 29, 2010 at 3:27 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> On Jul 29, 2010, at 3:06 PM, Yujie wrote:
>
>> Dear PETSc developers,
>>
>> When the program based on PETSc runs in parallel mode, how much size
>> of the matrix can MatLoad load?
>
>   Currently the limit is that each individual process cannot hold more then 2 billion nonzeros when using MatLoad(). So if you have more processes you can hold as big a matrix as you want. Within a few days PETSc-dev will eliminate this limit (which comes from how we use MPI).
>
>  But you need to ./configure PETSc with the option --with-64-bit-indices and need an operating system that supports 64 bit points (which you likely have).
>
>> Does the program need to save the whole matrix in one CPU,
>
>  No, absolutely NOT.
>
>
>  Barry
>
>
>> or is each
>> CPU in charge of the part of the matrix?
>>
>> For example, I have one matrix of ~30G. There are two CPUs on each
>> nodes with totally16G memory. I have 8 nodes. I use 16CPUs for
>> running. Can I load this matrix using MatLoad? Thanks a lot.
>>
>> Regards,
>> Yujie
>
>