[petsc-users] questions

[Barry Smith]

On Nov 17, 2011, at 2:21 PM, Ethan Coon wrote:

> On Thu, 2011-11-17 at 13:35 -0600, xiaohl wrote:
>> Hi Mike
>> 
>> I created the binary file from a ASCII file by C.
>> How could I create a file which I could use for petsc with DM routine?
>> 
> 
> There are a few ways to do this, but the easiest options are -- 
> 
> 1. write a C program that creates a DM and a Vec, sets the values of the
> Vec, and calls VecView (like the example you quoted does).  
> 
> 2. use matlab or python/numpy to generate arrays of the correct
> size/type/order, and then save those arrays to Petsc Binary format using
> the scripts in $PETSC_DIR/bin/matlab and $PETSC_DIR/bin/pythonscripts

  You can also write a binary file directly from C (or maybe Fortran) using the EXACT format as indicated in the manual page http://www.mcs.anl.gov/petsc/snapshots/petsc-current/docs/manualpages/Vec/VecLoad.html

   Barry


> 
> 
> Ethan
> 
>> Hailong
>> 
>> On Wed, 2 Nov 2011 15:53:27 -0500, Barry Smith <bsmith at mcs.anl.gov> 
>> wrote:
>>> On Nov 2, 2011, at 3:42 PM, Matthew Knepley wrote:
>>> 
>>>> On Wed, Nov 2, 2011 at 8:38 PM, xiaohl <xiaohl at ices.utexas.edu> 
>>>> wrote:
>>>> Hi
>>>> 
>>>> I am going to implement cell center difference method for
>>>> u = - K grad p
>>>> div u = f
>>>> where p is the pressure , u is the velocity, f is the source term.
>>>> 
>>>> my goal is to assemble the matrix and test the performance of 
>>>> different linear solvers in parallel.
>>>> 
>>>> my question is how can I read the input file for K where K is n*n 
>>>> tensor.
>>>> 
>>>> MatLoad()
>>> 
>>>   Hm, I think you should use a DMDA with n*n size dof and then use
>>> VecLoad() to load the entries of K.
>>> 
>>>   Barry
>>> 
>>>> 
>>>> second one is that do you have any similar examples?
>>>> 
>>>> Nothing with the mixed-discretization of the Laplacian.
>>>> 
>>>>   Matt
>>>> 
>>>> Hailong
>>>> 
>>>> 
>>>> 
>>>> --
>>>> What most experimenters take for granted before they begin their 
>>>> experiments is infinitely more interesting than any results to which 
>>>> their experiments lead.
>>>> -- Norbert Wiener
>> 
> 
> -- 
> ------------------------------------
> Ethan Coon
> Post-Doctoral Researcher
> Applied Mathematics - T-5
> Los Alamos National Laboratory
> 505-665-8289
> 
> http://www.ldeo.columbia.edu/~ecoon/
> ------------------------------------
>