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

68 HP MLIB User’s Guide

SAXPYI/DAXPYI/CAXPYI/ZAXPYI Sparse elementary vector operation

Name SAXPYI/DAXPYI/CAXPYI/ZAXPYI

Sparse elementary vector operation

Purpose Given a real or complex scalar a, a sparse vector x stored in compact form via a

set of indices and a dense vector y stored in full storage form, these

subprograms perform the elementary vector operation

More precisely, let x be a sparse n-vector with m ≤ n interesting (usually

nonzero) elements, and let {k

, k

, ..., k

} be the indices of these elements. All

uninteresting elements of x are assumed to be zero. Let y be an ordinary

n-vector. If x is represented by arrays x and indx such that indx(i)=k

and

x(i)=x

then these subprograms compute

Usage VECLIB:

INTEGER*4 m, indx(m)

REAL*4 a, x(m), y(n)

CALL SAXPYI(m, a, x, indx, y)

INTEGER*4 m, indx(m)

REAL*8 a, x(m), y(n)

CALL DAXPYI(m, a, x, indx, y)

INTEGER*4 m, indx(m)

COMPLEX*8 a, x(m), y(n)

CALL CAXPYI(m, a, x, indx, y)

INTEGER*4 m, indx(m)

COMPLEX*16 a, x(m), y(n)

CALL ZAXPYI(m, a, x, indx, y)

VECLIB8:

INTEGER*8 m, indx(m)

REAL*4 a, x(m), y(n)

CALL SAXPYI(m, a, x, indx, y)

INTEGER*8 m, indx(m)

REAL*8 a, x(m), y(n)

CALL DAXPYI(m, a, x, indx, y)

yax← y.+

,+← i 12… m.,, ,=