Dear Roy,

On Wed, 25 Feb 2009, Tim Kroeger wrote:

> On Wed, 25 Feb 2009, Tim Kroeger wrote:
>
>> I'm currently trying to test the ghosted vectors on my application,
>> but the queue on the cluster is full, so I have to wait.
>
> Update: My application crashes with the ghosted vectors, but I'm not
> yet sure whether it's a bug in the ghosted code or a bug in my
> application that just got triggered by the ghost dofs.  I'll try to
> track this down, but that will be next week.

Update: It doesn't crash any more.  With the patch that I sent you in 
the previous mail, it seems to work.  Well, at least the first 8 time 
steps of my application do the same as they did without the ghost 
dofs.  And the memory requirements are less than 50% of before (on 8 
processors).

However, (a) the results do not *exactly* coincide with the previous 
ones; that it, I get e.g. a residual norm of 1.16562e-08 instead of 
1.16561e-08 after 608 linear iterations (although using the same 
number of processors), and (b) I had to add a.close() between a=b and 
a.scale(), where a and b are *System::solution of two different 
systems.

Both facts surprise me.  In particular, (b) surprises me for two 
reasons, that is (b1) PetscVector::operator=(const PetscVector&) 
should not require closing the vector afterwards, and (b2) I wonder 
whether (and, if yes, why) you are using ghosted vectors for 
System::solution; I thought you were using them only for 
System::current_local_solution.

What do you think?  Does this look like more errors or not?

Best Regards,

Tim

-- 
Dr. Tim Kroeger
tim.kroe...@mevis.fraunhofer.de            Phone +49-421-218-7710
tim.kroe...@cevis.uni-bremen.de            Fax   +49-421-218-4236

Fraunhofer MEVIS, Institute for Medical Image Computing
Universitaetsallee 29, 28359 Bremen, Germany


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