NAG Library Routine Document

F06GRF (ZDOTUI)

+− Contents

1 Purpose

9 Example

F06GRF (ZDOTUI) computes the scalar product of an unconjugated sparse complex vector with a complex vector.

FUNCTION F06GRF (

COMPLEX (KIND=nag_wp) F06GRF

INTEGER	NZ, INDX(*)
COMPLEX (KIND=nag_wp)	X(), Y()

The routine may be called by its BLAS name zdotui.

F06GRF (ZDOTUI) returns, via the function name, the value of the scalar product

x^{T} y

where

x

is a sparse complex vector stored in compressed form, and

y

is a complex vector in full storage form.

Dodson D S, Grimes R G and Lewis J G (1991) Sparse extensions to the Fortran basic linear algebra subprograms ACM Trans. Math. Software 17 253–263

1: NZ – INTEGERInput: On entry: the number of nonzeros in the sparse vector $x$ .
2: X( $*$ ) – COMPLEX (KIND=nag_wp) arrayInput: Note: the dimension of the array X must be at least $\max (1, NZ)$ .
On entry: the compressed vector $x$ . X contains $x_{i}$ for $i \in J$ .
3: INDX( $*$ ) – INTEGER arrayInput: Note: the dimension of the array INDX must be at least $\max (1, NZ)$ .
On entry: INDX must contain the set of indices $J$ .
4: Y( $*$ ) – COMPLEX (KIND=nag_wp) arrayInput: Note: the dimension of the array Y must be at least $\max_{k} \{INDX (k)\}$ .
On entry: the vector $y$ . Only elements corresponding to indices in INDX are accessed.