# EPSGetStartVector

Gets a suitable vector to be used as the starting vector for the recurrence that builds the right subspace.

### Synopsis

    #include "slepceps.h"
    PetscErrorCode EPSGetStartVector(EPS eps,PetscInt i,Vec vec,PetscBool *breakdown)

Collective on EPS and Vec

### Input Parameters

| eps | - the eigensolver context
| i | - iteration number

### Output Parameters

| vec | - the start vector
| breakdown | - flag indicating that a breakdown has occurred

### Notes

The start vector is computed from another vector: for the first step (i=0), the first initial vector is used (see EPSSetInitialSpace()); otherwise a random vector is created. Then this vector is forced to be in the range of OP (only for generalized definite problems) and orthonormalized with respect to all V-vectors up to i-1.

The flag breakdown is set to true if either i=0 and the vector belongs to the deflation space, or i>0 and the vector is linearly dependent with respect to the V-vectors.

The caller must pass a vector already allocated with dimensions conforming to the initial vector. This vector is overwritten.

### See Also

EPSSetInitialSpace()

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