Re: [petsc-users] How to solve the pressure possion equations with four neuman bc

2016-09-25 Thread Matthew Knepley
On Sun, Sep 25, 2016 at 4:06 AM, 丁老师 wrote: > Dear professor: > In the ksp example ex50.c, i do not understand the meaning of > *KSPSolve* > > *(ksp,NULL,NULL);* > > *

Re: [petsc-users] How to solve the pressure possion equations with four neuman bc

2016-09-25 Thread 丁老师
Dear professor: In the ksp example ex50.c, i do not understand the meaning of KSPSolve(ksp,NULL,NULL); nMatNullSpaceCreate(PETSC_COMM_WORLD,PETSC_TRUE,0,0,); What is the meaning of NULL in the kspsolve. and two "0" in the MatNullSpaceCreate. Regards At 2016-09-24

Re: [petsc-users] How to solve the pressure possion equations with four neuman bc

2016-09-23 Thread Kong, Fande
Any references on this topic except the users manual? I am interested in mathematics theory on this topic. Fande Kong, On Fri, Sep 23, 2016 at 9:58 AM, Jed Brown wrote: > 丁老师 writes: > > > Dear friends: > > In the projection method for the solution

Re: [petsc-users] How to solve the pressure possion equations with four neuman bc

2016-09-23 Thread Jed Brown
"Kong, Fande" writes: > Any references on this topic except the users manual? I am interested in > mathematics theory on this topic. These are relevant. I've only skimmed them briefly, but they might suggest ways to improve PETSc's handling of singular systems. The

Re: [petsc-users] How to solve the pressure possion equations with four neuman bc

2016-09-23 Thread Jed Brown
丁老师 writes: > Dear friends: > In the projection method for the solution of incompressible flow, a > pressure equation with four neuman bcs need to be solved. > but the pressure matrix is singular. it gives divergence solution. how to > solve this kind of equations.

Re: [petsc-users] How to solve the pressure possion equations with four neuman bc

2016-09-23 Thread Matthew Knepley
On Fri, Sep 23, 2016 at 9:38 AM, 丁老师 wrote: > Dear friends: > In the projection method for the solution of incompressible flow, a > pressure equation with four neuman bcs need to be solved. > but the pressure matrix is singular. it gives divergence solution. how to >

[petsc-users] How to solve the pressure possion equations with four neuman bc

2016-09-23 Thread 丁老师
Dear friends: In the projection method for the solution of incompressible flow, a pressure equation with four neuman bcs need to be solved. but the pressure matrix is singular. it gives divergence solution. how to solve this kind of equations. Regards