Matlab and PETSc communication

[Matthew Knepley]

On Mon, Jul 21, 2008 at 10:14 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> On Jul 21, 2008, at 7:57 PM, Michel Cancelliere wrote:
>
>> Hi, I am a new user of PETSc. I am working in Reservoir Simulation and I
>> have been developing the simulator inside Matlab. I have some question in
>> order to understand better my possibilities of success in what I want to do:
>>
>>        • I want to solve the linear system obtained from the inner
>> iterations in the newton method using PETSc, is it possible to communicate
>> in an efficient way PETSc  with Matlab to do that? I now that I can write
>> binary files and then read with PETSc but due the size of the matrix it is a
>> very time-expensive way. Where i can find some examples? I look at the
>> examples within the package but I could not find it. \
>>        • It is possible to call PETSc library inside Matlab? Using the Mex
>> files and Matlab compiler?
>
>   There is no code to do this. It is possible but pretty complicated to
> write the appropriate Mex code. (Because
> each Mex function is a separate shared library you cannot just write a Mex
> function for each PETSc function since they
> would not share the PETSc global variables. You would have to write one Mex
> function that is a "gatekeeper" and calls
> the requested PETSc function underneath. I've monkeyed with this a few times
> but did not have the time/energy/intellect
> to write code to automate this process. Give me 300,000 dollars and we could
> hire someone to write this :-)
>
>  You might look at the "newly improved" socket interface in petsc-dev
> (http://www-unix.mcs.anl.gov/petsc/petsc-as/developers/index.html).
> With this you write a stand alone C PETSc program that waits at a socket,
> receive the matrix and right hand side and then
> sends back the solution. The code for marshalling the matrices and vector is
> common between the sockets and binary files.
> On the Matlab side you create a "file" that is actually a socket connection.
> See src/sys/viewer/impls/socket/matlab This may
> take a little poking around and you asking us a couple of questions to get
> it.
> Note there is no inherent support for parallelism on the PETSc side with
> this setup but I think it is possible.

I personally think this would be much easier in Sage than in Matlab
proper. In fact,
with Sage you could use petsc4py directly, and directly access the
data structures
as numpy arrays if necessary.

  Matt

>   Barry
>
>
>> Thank you very much for your time,
>>
>> Michel Cancelliere
>
>



-- 
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