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# SNESLINESEARCHNLEQERR
Error-oriented affine-covariant globalised Newton algorithm of Deuflhard (2011). This linesearch is intended for Newton-type methods which are affine covariant. Affine covariance
means that Newton's method will give the same iterations for F(x) = 0 and AF(x) = 0 for a nonsingular
matrix A. This is a fundamental property; the philosophy of this linesearch is that globalisations
of Newton's method should carefully preserve it.


## Options Database Keys

- ***-snes_linesearch_damping<1.0> -*** initial step length
- ***-snes_linesearch_minlambda<1e-*** 12> - minimum step length allowed





## Note
Contributed by Patrick Farrell <patrick.farrell@maths.ox.ac.uk>


## Reference

- ***- * -*** Newton Methods for Nonlinear Problems, Deuflhard, P. 2011, Springer-Verlag, page 148



## See Also
 `SNESLineSearch`, `SNES`, `SNESLineSearchCreate()`, `SNESLineSearchSetType()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/linesearch/impls/nleqerr/linesearchnleqerr.c.html#SNESLINESEARCHNLEQERR">src/snes/linesearch/impls/nleqerr/linesearchnleqerr.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/snes/linesearch/impls/nleqerr/linesearchnleqerr.c)


[Index of all SNES routines](index.md)  
[Table of Contents for all manual pages](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)