SDOT/DDOT/CDOTC/CDOTU/ZDOTC/ZDOTU

 

 

 

Dot product

 

x

Array of length lenx = (n−1)⋅incx+1 containing the

 

 

n-vector x. x is used in conjugated form by CDOTC and

 

 

ZDOTC and in unconjugated form by the other

 

 

subprograms.

 

 

incx

Increment for the array x:

 

 

incx ≥ 0

x is stored forward in array x; that is,

 

 

 

 

 

xi is stored in x((i−1)⋅incx+1).

 

 

incx < 0

x is stored backward in array x; that

 

 

 

 

 

is, xi is stored in x((i−n)⋅incx+1).

 

 

Use incx = 1 if the vector x is stored contiguously in

 

 

array x; that is, if xi is stored in x(i). Refer to “BLAS

 

 

Indexing Conventions” in the introduction to this

 

 

chapter.

 

 

y

Array of length leny = (n−1)⋅incy+1 containing the

 

 

n-vector y.

 

 

incy

Increment for the array y:

 

 

incy ≥ 0

y is stored forward in array y; that is,

 

 

 

 

 

yi is stored in y((i−1)⋅incy+1).

 

 

incy < 0

y is stored backward in array y; that

 

 

 

 

 

is, yi is stored in y((i−n)⋅incy+1).

 

 

Use incy = 1 if the vector y is stored contiguously in

 

 

array y; that is, if yi is stored in y(i). Refer to “BLAS

 

 

Indexing Conventions” in the introduction to this

 

 

chapter.

 

 

res

Pointer to output (for use with Intel compilers only).

Output

s

The resulting value of the dot product. If n ≤ 0 , then

 

 

s = 0 . Otherwise,

 

 

n

 

 

 

s = ∑ xi yi

 

 

 

i = 1

 

 

 

unless the subprogram name is CDOTC or ZDOTC, in

 

 

which case

 

 

 

n

 

 

 

s = ∑

x

i yi

 

 

 

i = 1

 

Notes

If incx = 0, then xi = x(1) for all i. If incy = 0, then yi = y(1) for all i. In either

 

of these cases, another VECLIB subprogram would be more efficient.

86HP MLIB User’s Guide