[petsc-users] (no subject)

[Barry Smith]

   The snes options are not relevant since the parts of a PCFIELDSPLIT are always linear problems.

    By default PCFIELDSPLIT uses a KSP type of preonly on each split (that is it applies the preconditioner exactly once inside the PCApply_FieldSplit() hence the -fieldsplit_*_ksp_ options are not relevent. You can use -fieldsplit_ksp_type gmres for example to have it use gmres on each of the splits, but note that then you should use -ksp_type fgmres since using gmres inside a preconditioner results in a nonlinear preconditioner.

    You can always run with -ksp_view to see the solver being used and the prefixes that currently make sense.

  Barry


> On Dec 11, 2023, at 2:51 AM, 1807580692 <1807580692 at qq.com> wrote:
> 
> Hello, I have encountered some problems. Here are some of my configurations.
> OS Version and Type:  Linux daihuanhe-Aspire-A315-55G 5.15.0-89-generic #99~20.04.1-Ubuntu SMP Thu Nov 2 15:16:47 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
> PETSc Version: #define PETSC_VERSION_RELEASE    1
> 		#define PETSC_VERSION_MAJOR      3
> 		#define PETSC_VERSION_MINOR      19
> 		#define PETSC_VERSION_SUBMINOR   0
> 		#define PETSC_RELEASE_DATE       "Mar 30, 2023"
> 		#define PETSC_VERSION_DATE       "unknown"
> MPI implementation: MPICH	
> Compiler and version: Gnu C
> The problem is when I type 
> “mpiexec -n 4 ./ex19 -lidvelocity 100 -prandtl 0.72 -grashof 10000 -da_grid_x 64 -da_grid_y 64 -snes_type newtonls -ksp_type gmres -pc_type fieldsplit -pc_fieldsplit_type symmetric_multiplicative -pc_fieldsplit_block_size 4 -pc_fieldsplit_0_fields 0,1,2,3 -pc_fieldsplit_1_fields 0,1,2,3 -fieldsplit_0_pc_type asm -fieldsplit_0_pc_asm_type restrict -fieldsplit_0_pc_asm_overlap 5 -fieldsplit_0_sub_pc_type lu -fieldsplit_1_pc_type asm -fieldsplit_1_pc_asm_type restrict -fieldsplit_1_pc_asm_overlap 5 -fieldsplit_1_sub_pc_type lu  -snes_monitor -snes_converged_reason -fieldsplit_0_ksp_atol 1e-10  -fieldsplit_1_ksp_atol 1e-10  -fieldsplit_0_ksp_rtol 1e-6  -fieldsplit_1_ksp_rtol 1e-6 -fieldsplit_0_snes_atol 1e-10  -fieldsplit_1_snes_atol 1e-10  -fieldsplit_0_snes_rtol 1e-6  -fieldsplit_1_snes_rtol 1e-6”
> in the command line, where my path is /petsc/src/snes/tutorials.
> 
> It returns 
> “WARNING! There are options you set that were not used!
> WARNING! could be spelling mistake, etc!
> There are 8 unused database options. They are:
> Option left: name:-fieldsplit_0_ksp_atol value: 1e-10 source: command line
> Option left: name:-fieldsplit_0_ksp_rtol value: 1e-6 source: command line
> Option left: name:-fieldsplit_0_snes_atol value: 1e-10 source: command line
> Option left: name:-fieldsplit_0_snes_rtol value: 1e-6 source: command line
> Option left: name:-fieldsplit_1_ksp_atol value: 1e-10 source: command line
> Option left: name:-fieldsplit_1_ksp_rtol value: 1e-6 source: command line
> Option left: name:-fieldsplit_1_snes_atol value: 1e-10 source: command line
> Option left: name:-fieldsplit_1_snes_rtol value: 1e-6 source: command line”.
> Please tell me what should I do?Thank you very much.
> 	
> 1807580692
> 1807580692 at qq.com
>  <https://wx.mail.qq.com/home/index?t=readmail_businesscard_midpage&nocheck=true&name=1807580692&icon=http%3A%2F%2Fthirdqq.qlogo.cn%2Fg%3Fb%3Dsdk%26k%3DsDkxrKtOBYniaVteAHHIz5g%26s%3D100%26t%3D1647684318%3Frand%3D1648799506&mail=1807580692%40qq.com&code=>
>  

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