HP MLIB User's Guide Vol. 2 7th Ed.

Chapter 12 VMATH 861

Pack (gather) a vector with speciﬁed indexing into a contiguous vector vspacki, vspackv, vspackm, vdpacki,

vdpackv, vdpackm

Name vspacki, vspackv, vspackm, vdpacki, vdpackv, vdpackm

Pack (gather) a vector with speciﬁed indexing into a contiguous vector

Purpose vspacki and vdpacki pack the vector of n elements stored (forward) with

increment inca in array a into a contiguous vector in array y:

y(i) = a(1+(i-1)*inca), for 1 = 1 to n

vspackv and vdpackv pack the vector of elements in array a, with index vector

in array ia, into a contiguous vector in array y:

y(i) = a(ia(i)+1), for i = 1 to n

The index vector values 0, ..., n-1 represent Fortran array indices 1, ..., n (as in

Intel’s VML). Hence, index value ia(i) indicates array entry a(ia(i)+1).

vspackm and vdpackm pack the vector of elements in array a, speciﬁed by the

mask vector of n elements in array ma, into a contiguous vector in array y:

initialize j = 0

if (m(i)) then y(j) = a(i) and j = j+1, for i = 1 to n

Usage The Fortran include ﬁle math.ﬁ declares interfaces for these subroutines,

suitable for both VMATH and VMATH8. The interfaces are compatible with

Intel’s MKL VML (Vector Math Library).

SUBROUTINE vspacki(n, a, inca, y)

INTEGER, INTENT(IN) :: n, inca

REAL (KIND=4), DIMENSION(n), INTENT(IN) :: a

REAL (KIND=4), DIMENSION(n), INTENT(OUT):: y

SUBROUTINE vspackv(n, a, ia, y)

INTEGER, INTENT(IN) :: n

REAL (KIND=4), DIMENSION(n), INTENT(IN) :: a

INTEGER, DIMENSION(n), INTENT(IN) :: ia

REAL (KIND=4), DIMENSION(n), INTENT(OUT):: y

SUBROUTINE vspackm(n, a, ma, y)

INTEGER, INTENT(IN) :: n

REAL (KIND=4), DIMENSION(n), INTENT(IN) :: a

INTEGER, DIMENSION(n), INTENT(IN) :: ma

REAL (KIND=4), DIMENSION(n), INTENT(OUT):: y