[petsc-users] use kspsolve repeately

[丁老师]

   thank you . but the matrix element has been changed in the third and fourth call. how to re calculate the preconditioner.






在 2013-08-24 18:18:17，"Matthew Knepley" <knepley at gmail.com> 写道：



On Sat, Aug 24, 2013 at 4:57 AM, 丁老师 <ztdepyahoo at 163.com> wrote:

in  my code, i need to use kspsolve in the following way

    KSP ksp;
 
    KSPCreate(PETSC_COMM_WORLD,&ksp);
    KSPSetOperators(ksp,A,A,SAME_NONZERO_PATTERN);
    KSPSetOperators(ksp,A,A,SAME_PRECONDITIONER);
    KSPSetInitialGuessNonzero(ksp,PETSC_TRUE)
     KSPSetType(ksp,KSPBCGS);    
    KSPSetFromOptions(ksp);   

  set the matrix A value and right hand side bu and bv.
    kspsolve(A,bu);
    kspsolve(A,bv);
  change the value of matrix A and bu bv,
     kspsolve(A,bu);
     kspsolve(A,bv);
 
 the first and second call to the kspsolve use the same preconditioner. but which preconditoner does the third and fourth call to the kspsolve since the value of the matrix A has changed.



The first call is redundant, and the subsequent solves use the same preconditioner, as you asked.


   Matt
 
 










--
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener
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