Huq:
# define PETSC_MACHINE_EPSILON 2.2204460492503131e-16
See /petsc/include/petscmath.h
Hong
Hello PETSc developers,
I went through the ex23.c of ksp section attached herewith but I don't
understand the following part:
***********************************************
tol=1000.*PETSC_MACHINE_EPSILON
************************************************
and,
************************************************
ierr = VecAXPY(x,-1.0,u);CHKERRQ(ierr);
ierr = VecNorm(x,NORM_2,&norm);CHKERRQ(ierr);
ierr = KSPGetIterationNumber(ksp,&its);CHKERRQ(ierr);
if (norm > tol) {
ierr = PetscPrintf(PETSC_COMM_WORLD,"Norm of error %g, Iterations %D\n",
(double)norm,its);CHKERRQ(ierr);
}
************************************************
I don't understand what is "tol" here and "*PETSC_MACHINE_EPSILON"?
The if condition is also not clear to me.
Thanks.
Sincerely,
Huq
--
Fazlul Huq
Graduate Research Assistant
Department of Nuclear, Plasma & Radiological Engineering (NPRE)
University of Illinois at Urbana-Champaign (UIUC)
E-mail: [email protected]<mailto:[email protected]>
