# EPSComputeResidualNorm

Computes the norm of the residual vector associated with the i-th computed eigenpair.

### Synopsis

    #include "slepceps.h"
    PetscErrorCode EPSComputeResidualNorm(EPS eps,PetscInt i,PetscReal *norm)

Collective on EPS

### Input Parameter

| eps | - the eigensolver context
| i | - the solution index

### Output Parameter

norm - the residual norm, computed as ||Ax-kBx||_2 where k is the eigenvalue and x is the eigenvector. If k=0 then the residual norm is computed as ||Ax||_2.

### Notes

The index i should be a value between 0 and nconv-1 (see EPSGetConverged()). Eigenpairs are indexed according to the ordering criterion established with EPSSetWhichEigenpairs().

### See Also

EPSSolve(), EPSGetConverged(), EPSSetWhichEigenpairs()

Location: src/eps/interface/solve.c
Index of all EPS routines
Table of Contents for all manual pages
Index of all manual pages