SNESGetIterationNumber — PETSc 3.21.4 documentation

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# SNESGetIterationNumber

Gets the number of nonlinear iterations completed in the current or most recent `SNESSolve()`

## Synopsis

    #include "petscsnes.h"
    PetscErrorCode SNESGetIterationNumber(SNES snes, PetscInt *iter)

Not Collective

## Input Parameter

- snes - `SNES` context

## Output Parameter

- iter - iteration number

## Notes

For example, during the computation of iteration 2 this would return 1.

This is useful for using lagged Jacobians (where one does not recompute the Jacobian at each `SNES` iteration). For example, the code

          ierr = SNESGetIterationNumber(snes,&it);
          if (!(it % 2)) {
            [compute Jacobian here]
          }

can be used in your function that computes the Jacobian to cause the Jacobian to be recomputed every second `SNES` iteration. See also `SNESSetLagJacobian()`

After the `SNES` solve is complete this will return the number of nonlinear iterations used.

## See Also

SNES: Nonlinear Solvers, `SNES`, `SNESSolve()`, `SNESSetLagJacobian()`, `SNESGetLinearSolveIterations()`, `SNESSetMonitor()`

## Level

intermediate

## Location

src/snes/interface/snes.c

## Examples

src/snes/tutorials/ex21.c
src/snes/tutorials/ex2.c
src/snes/tutorials/ex14.c
src/snes/tutorials/ex46.c
src/snes/tutorials/ex42.c
src/snes/tutorials/ex18.c
src/snes/tutorials/ex15.c
src/snes/tutorials/ex16.c
src/snes/tutorials/ex25.c
src/snes/tutorials/ex19.c

Index of all SNES routines
Table of Contents for all manual pages
Index of all manual pages