User-difined PC

Barry Smith bsmith at
Mon Sep 22 11:08:09 CDT 2008

On Sep 22, 2008, at 7:59 AM, Dave May wrote:

> Why is the first pointer in PCSHELL operations the user context
> whereas in MATSHELL the first pointer is of type Mat ?? Seems slightly
> inconsistent.
    Good question, these were done at different times and only later
did we realize the inconsistency. This is something that should be  
fixed in petsc-dev.


I guess the first argument for the PCSHELL should become the pc.

> On Mon, Sep 22, 2008 at 8:31 PM, Michel Cancelliere
> <fernandez858 at> wrote:
>> Hello,
>> I have problems with the implementation of a user-defined pc,  
>> basically my
>> program is in a cycle, for with which he is called by matlab each  
>> time it
>> seeks to solve a linear system, the problem is that in the first  
>> iteration
>> of the for-cycle  the preconditioner works very well, then fails to
>> convergence. It may be some parameters that I setting wrong?
>> I'am attaching my program code.
>> Thank you,
>> Michel

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