# QEPSetInitialSpaceLeft

Specify a basis of vectors that constitute the initial left space, that is, the subspace from which the solver starts to iterate for building the left subspace (in methods that work with two subspaces).

### Synopsis

    #include "slepcqep.h"
    PetscErrorCode QEPSetInitialSpaceLeft(QEP qep,PetscInt n,Vec *is)

Collective on QEP and Vec

### Input Parameter

| qep | - the quadratic eigensolver context
| n | - number of vectors
| is | - set of basis vectors of the initial left space

### Notes

Some solvers start to iterate on a single vector (initial left vector). In that case, the other vectors are ignored.

These vectors do not persist from one QEPSolve() call to the other, so the initial left space should be set every time.

The vectors do not need to be mutually orthonormal, since they are explicitly orthonormalized internally.

Common usage of this function is when the user can provide a rough approximation of the wanted left eigenspace. Then, convergence may be faster.

### See Also

QEPSetInitialSpace()

Location: src/qep/interface/qepsetup.c
Index of all QEP routines
Table of Contents for all manual pages
Index of all manual pages