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

Chapter 3 Basic Matrix Operations 405
Triangular packed matrix-vector multiply F_STPMV/F_DTPMV/F_CTPMV/F_ZTPMV
INCX Increment for the array x. A vector x having component
x
i
, i = 1,..., n, is stored in an array X() with increment
argument incx. If incx > 0 then x
i
is stored in
X (1 + (i - 1) x incx). If incx < 0 then x
i
is stored in
X (1 + (N - i) x |incx|). incx = 0 is an illegal value.
Output X The updated X vector replaces the input.