# KSPSolve

Solves linear system.

### Synopsis

    #include "petscksp.h"
    PetscErrorCode PETSCKSP_DLLEXPORT KSPSolve(KSP ksp,Vec b,Vec x)

Collective on KSP

### Parameter

| ksp | - iterative context obtained from KSPCreate()
| b | - the right hand side vector
| x | - the solution (this may be the same vector as b, then b will be overwritten with answer)

### Options Database Keys

| -ksp_compute_eigenvalues | - compute preconditioned operators eigenvalues
| -ksp_plot_eigenvalues | - plot the computed eigenvalues in an X-window
| -ksp_compute_eigenvalues_explicitly | - compute the eigenvalues by forming the dense operator and useing LAPACK
| -ksp_plot_eigenvalues_explicitly | - plot the explicitly computing eigenvalues
| -ksp_view_binary | - save matrix and right hand side that define linear system to the default binary viewer (can be read later with src/ksp/examples/tutorials/ex10.c for testing solvers)
| -ksp_converged_reason | - print reason for converged or diverged
| -ksp_final_residual | - print 2-norm of true linear system residual at the end of the solution process
| -ksp_view | - print the ksp data structure at the end of the system solution

### Notes

The operator is specified with PCSetOperators().

Call KSPGetConvergedReason() to determine if the solver converged or failed and why. The number of iterations can be obtained from KSPGetIterationNumber().

If using a direct method (e.g., via the KSP solver KSPPREONLY and a preconditioner such as PCLU/PCILU), then its=1. See KSPSetTolerances() and KSPDefaultConverged() for more details.

### Understanding Convergence

The routines KSPMonitorSet(), KSPComputeEigenvalues(), and KSPComputeEigenvaluesExplicitly() provide information on additional options to monitor convergence and print eigenvalue information.

### Keywords

KSP, solve, linear system

### See Also

KSPCreate(), KSPSetUp(), KSPDestroy(), KSPSetTolerances(), KSPDefaultConverged(),
KSPSolveTranspose(), KSPGetIterationNumber()

Level:beginner
Location:src/ksp/ksp/interface/itfunc.c
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages src/ksp/pc/examples/tutorials/ex1.c.html
src/ksp/pc/examples/tutorials/ex2.c.html
src/ksp/ksp/examples/tutorials/ex1.c.html
src/ksp/ksp/examples/tutorials/ex2.c.html
src/ksp/ksp/examples/tutorials/ex3.c.html
src/ksp/ksp/examples/tutorials/ex4.c.html
src/ksp/ksp/examples/tutorials/ex5.c.html
src/ksp/ksp/examples/tutorials/ex7.c.html
src/ksp/ksp/examples/tutorials/ex8.c.html
src/ksp/ksp/examples/tutorials/ex9.c.html