ell1 norm convergence test

[Ryan Yan]

Hi All,
The following question is only for test and comparison reason.

Is there a command line option to set up using 1-Norm(sum of absolute value
of residuals)  as convergence monitor and test.

Alternatively, if I can get the residual "r" out at the end of each
iteration, then it is going to be much simpler, since I can just call
VecNorm(r, NORM_1, &r_ell1) and pass the r_ell1 into the convergence monitor
and test. Can anyone inform me if PETSc has an interface for the resuidual
r?

Or one has to call the convergence test:
MyKSPConverged(ksp,n,rnorm,flag,dummy);
and following the steps:
1. fetch the exact solution:

KSPBuildSolution(ksp,PETSC_NULL_OBJECT,x,ierr)

2. calculate the residual:

pass the Right Hand side and the Matrix in to calculate the 1-Norm. But this
step is *not* obvious, since the matrix and rhs is already distributed over
each processes.

3. set up the convergence test based on the 1_Norm residual.


Thank you very much,


Yan
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