slepc-3.22.1 2024-10-28
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# BVDotColumn

Computes multiple dot products of a column against all the previous columns of a BV.

### Synopsis

    #include "slepcbv.h"
    PetscErrorCode BVDotColumn(BV X,PetscInt j,PetscScalar *q)

Collective

### Input Parameters

| X | - basis vectors
| j | - the column index

### Output Parameter

| q | - an array where the result must be placed

### Notes

This operation is equivalent to BVDotVec() but it uses column j of X rather than taking a Vec as an argument. The number of active columns of X is set to j before the computation, and restored afterwards. If X has leading columns specified, then these columns do not participate in the computation. Therefore, the length of array q must be equal to j minus the number of leading columns.

### Developer Notes

If q is NULL, then the result is written in position nc+l of the internal buffer vector, see BVGetBufferVec().

### See Also

BVDot(), BVDotVec(), BVSetActiveColumns(), BVSetMatrix()

### Level

advanced

### Location

src/sys/classes/bv/interface/bvglobal.c
Index of all BV routines
Table of Contents for all manual pages
Index of all manual pages