HP MLIB User's Guide Vol. 1 7th Ed.

Chapter 3 Basic Matrix Operations 383
Symmetric packed matrix-vector multiply F_SSPMV/F_DSPMV/F_CSPMV/F_ZSPMV
INCY Increment for the array y. A vector y having component
y
i
, i = 1,..., n, is stored in an array Y() with increment
argument incy. If incy > 0 then y
i
is stored in
Y(1 + (i - 1) x incy). If incy < 0 then y
i
is stored in
Y(1 + (N - i) x |incy|). incy = 0 is an illegal value.
Output Y The updated Y vector replaces the input.
y αAx βy with A=A
T
+←