[petsc-users] Question on writing a large matrix

[Aron Ahmadia]

Hi Vish,

What is 'painfully slow'.  Do you have a profile or an estimate in terms of
GB/s?  Have you taken a look at your process's memory allocation and checked
to see if it is swapping?  My first guess would be that you are exceeding
RAM and your program is thrashing as parts of the page table get swapped to
and from disk mid-run.

A

On Thu, Apr 21, 2011 at 5:39 PM, S V N Vishwanathan
<vishy at stat.purdue.edu>wrote:

> Hi
>
> I am using the attached code to convert a matrix from a rather
> inefficient ascii format (each line is a row and contains a series of
> idx:val pairs) to the PETSc binary format. Some of the matrices that I
> am working with are rather huge (50GB ascii file) and cannot be
> assembled on a single processor. When I use the attached code the matrix
> assembly across machines seems to be fairly fast. However, dumping the
> assembled matrix out to disk seems to be painfully slow. Any suggestions
> on how to speed things up will be deeply appreciated.
>
> vishy
>
>
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