[petsc-dev] (no subject)

[Barry Smith]

   Satish,

   How about removing the "snapshots" for all PETSc's before say 3.1? Maybe even 3.1?


     Barry


Begin forwarded message:

> From: Jed Brown <jedbrown at mcs.anl.gov>
> Date: September 29, 2011 2:00:13 PM CDT
> To: petsc-maint at mcs.anl.gov, Xiang Zheng <xz2208 at columbia.edu>
> Subject: Re: [petsc-maint #88797] Does anybody what the first two sentences mean?
> Reply-To: petsc-maint at mcs.anl.gov, Jed Brown <jedbrown at mcs.anl.gov>
> 
> You are using docs from an ancient version of PETSc, please look at the 3.2
> documentation.
> 
> http://www.mcs.anl.gov/petsc/petsc-as/documentation/index.html
> 
> 
> Please explain what you are trying to do and which examples you have looked
> at.
> 
> If you provide a DM, then a finite difference Jacobian with coloring is used
> automatically if you don't set your own Jacobian evaluation routine, see,
> e.g. src/snes/examples/tutorials/ex5.c.
> 
> On Thu, Sep 29, 2011 at 13:45, Xiang Zheng <xz2208 at columbia.edu> wrote:
> 
>> Dear Scholars,
>> 
>> I am learning how to set SNES.
>> 
>> However, when I checked the tutorial page below:
>> 
>> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-2.3.3/docs/manualpages/DA/DMMGSetSNES.html
>> 
>> It seems options in this page don't match. I am not sure if my
>> intuition is correct.
>> 
>> I want to use finite difference to approximate the Jacobian. But I am
>> not sure how to do it.
>> 
>> Therefore, I checked some examples suggested by PETSc. I found some
>> functions below:
>> 
>> DMMGSetSNES <
>> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-2.3.3/docs/manualpages/DA/DMMGSetSNES.html#DMMGSetSNES
>>> (dmmg,FormFunction,0);
>> 
>> DMMGSetSNES <
>> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-2.3.3/docs/manualpages/DA/DMMGSetSNES.html#DMMGSetSNES
>>> (dmmg,FormFunction,PETSC_NULL
>> <
>> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-2.3.3/docs/manualpages/Sys/PETSC_NULL.html#PETSC_NULL
>>> );
>> 
>> DMMGSetSNES <
>> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-2.3.3/docs/manualpages/DA/DMMGSetSNES.html#DMMGSetSNES
>>> (dmmg,FormFunction,FormJacobian);
>> 
>> 
>> I can understand the third sentence. But I am not sure how the first two
>> sentences work.
>> In other words, I don't know what 0 and
>> PETSC_NULL<
>> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-2.3.3/docs/manualpages/Sys/PETSC_NULL.html#PETSC_NULL
>>> mean.
>> 
>> Does anybody what the first two sentences mean?
>> 
>> Thanks.
>> --
>> Xiang Zheng
>> Department of Applied Mathematics
>> Columbia University
>> New York NY 10027
>> 
>> 
>