[petsc-users] MatLUFactorNumeric_SeqAIJ() consumes long runtime

[Barry Smith]

   If you call KSPSetUp() directly it calls PCSetUp(). If you do not call KSPSetUp() directly it is called at the beginning of KSPSolve() the FIRST time KSPSolve() is called after a KSPSetOperators(). If KSPSolve() is called repeatedly without calling KSPSetFromOperators() again (meaning changing the right hand side but not the matrix) then KSPSetUp() is not called for those solves since the preconditioner has already been setup.

   Barry

On Oct 26, 2011, at 4:13 AM, Debao Shao wrote:

> When will "PCSetUp" set up new PC?
> 1), PCSetUp(): Setting up PC with same nonzero pattern
> 2), [0] PCSetUp(): Setting up new PC
> 
> Thanks,
> Debao
> -----Original Message-----
> From: petsc-users-bounces at mcs.anl.gov [mailto:petsc-users-bounces at mcs.anl.gov] On Behalf Of Barry Smith
> Sent: Tuesday, October 25, 2011 9:04 PM
> To: PETSc users list
> Subject: Re: [petsc-users] MatLUFactorNumeric_SeqAIJ() consumes long runtime
> 
> 
>  My guess is that the code is repeatedly trying larger and large shifts to get a nonzero pivot as it factors.  If you run with -info and let it run to completion it will print some information about the shifts it has tried.
> 
>    Barry
> 
> On Oct 25, 2011, at 3:45 AM, Debao Shao wrote:
> 
>> DA,
>> 
>> I'm using PETSc ILU(1)+GMRES to solve an QP problem. But the job may hang at "MatLUFactorNumeric_SeqAIJ()" for long time.
>> 
>> (gdb) bt
>> #0  0x0000000002284520 in MatLUFactorNumeric_SeqAIJ ()
>> #1  0x0000000002265f89 in MatLUFactorNumeric ()
>> #2  0x0000000002342ff3 in PCSetUp_ILU ()
>> #3  0x00000000024f8d65 in PCSetUp ()
>> #4  0x0000000002362964 in KSPSetUp ()
>> #5  0x0000000002363455 in KSPSolve ()
>> 
>> Do you have idea for such phenomenon?
>> 
>> Thanks,
>> Debao
>> 
>> -- The information contained in this communication and any attachments is confidential and may be privileged, and is for the sole use of the intended recipient(s). Any unauthorized review, use, disclosure or distribution is prohibited. Unless explicitly stated otherwise in the body of this communication or the attachment thereto (if any), the information is provided on an AS-IS basis without any express or implied warranties or liabilities. To the extent you are relying on this information, you are doing so at your own risk. If you are not the intended recipient, please notify the sender immediately by replying to this message and destroy all copies of this message and any attachments. ASML is neither liable for the proper and complete transmission of the information contained in this communication, nor for any delay in its receipt.
> 
> 
> -- The information contained in this communication and any attachments is confidential and may be privileged, and is for the sole use of the intended recipient(s). Any unauthorized review, use, disclosure or distribution is prohibited. Unless explicitly stated otherwise in the body of this communication or the attachment thereto (if any), the information is provided on an AS-IS basis without any express or implied warranties or liabilities. To the extent you are relying on this information, you are doing so at your own risk. If you are not the intended recipient, please notify the sender immediately by replying to this message and destroy all copies of this message and any attachments. ASML is neither liable for the proper and complete transmission of the information contained in this communication, nor for any delay in its receipt.