SGBMV/DGBMV/CGBMV/ZGBMV

Matrix-vector multiply

x

Array containing the vector x. The number of elements

 

of x and the value of lenx, the dimension of the array x,

 

depend on trans:

 

’N’ or ’n’

x has n elements lenx = (n−1)⋅incx+1

 

otherwise

x has m elements lenx = (m−1)⋅incx+1

incx

Increment for the array x, incx ≠ 0:

 

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, if trans = ’N’ or ’n’, then xi is stored

 

 

in x((i−n)⋅incx+1); otherwise, xi is

 

 

stored in x((i−m)⋅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

 

Chapter 2.

 

beta

The scalar β.

y

Array containing the vector y. The number of elements

 

of y and the value of leny, the dimension of the array y,

 

depend on trans:

 

’N’ or ’n’

y has m elements leny = (m−1)⋅incy+1

 

otherwise

y has n elements leny = (n−1)⋅incy+1

 

Not used as input if beta = 0.

incy

Increment for the array y, incy ≠ 0:

 

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, if trans = ’N’ or ’n’, then yi is stored

 

 

in y((i−m)⋅incy+1); otherwise, 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 Chapter 2.

216HP MLIB User’s Guide