petsc-3.7.3 2016-07-24
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# TaoDefaultComputeHessian

Computes the Hessian using finite differences.

### Synopsis

    #include "petsctao.h"
    PetscErrorCode TaoDefaultComputeHessian(Tao tao,Vec V,Mat H,Mat B,void *dummy)

Collective on Tao

### Input Parameters

| tao | - the Tao context
| V | - compute Hessian at this point
| dummy | - not used

### Output Parameters

| H | - Hessian matrix (not altered in this routine)
| B | - newly computed Hessian matrix to use with preconditioner (generally the same as H)

### Options Database Key

| -tao_fd | - Activates TaoDefaultComputeHessian()
| -tao_view_hessian | - view the hessian after each evaluation using PETSC_VIEWER_STDOUT_WORLD

### Notes

This routine is slow and expensive, and is not currently optimized to take advantage of sparsity in the problem. Although TaoDefaultComputeHessian() is not recommended for general use in large-scale applications, It can be useful in checking the correctness of a user-provided Hessian.

### See Also

TaoSetHessianRoutine(), TaoDefaultComputeHessianColor(), SNESComputeJacobianDefault(), TaoSetGradientRoutine(), TaoDefaultComputeGradient()

Level:advanced
Location: src/tao/interface/fdiff.c
Index of all Tao routines
Table of Contents for all manual pages
Index of all manual pages

### Examples

src/tao/unconstrained/examples/tutorials/minsurf2.c.html