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

94 HP MLIB User’s Guide
SGTHR/DGTHR/IGTHR/CGTHR/ZGTHR Gather sparse vector
Name SGTHR/DGTHR/IGTHR/CGTHR/ZGTHR
Gather sparse vector
Purpose Given a real, integer, or complex dense vector y stored in full storage form and a
set of indices of interesting elements of y, these subprograms gather those
elements into a sparse vector x stored in compact form via the set of indices.
More precisely, let {k
1
, k
2
, ..., k
m
} be the indices of the interesting elements. If x
is represented by arrays x and indx such that indx(i)=k
i
and x(i)=x
k
i
, then
Usage VECLIB:
INTEGER*4 m, indx(m)
REAL*4 y(n), x(m)
CALL SGTHR(m, y, x, indx)
INTEGER*4 m, indx(m)
REAL*8 y(n), x(m)
CALL DGTHR(m, y, x, indx)
INTEGER*4 m, indx(m), y(n), x(m)
CALL IGTHR(m, y, x, indx)
INTEGER*4 m, indx(m)
COMPLEX*8 y(n), x(m)
CALL CGTHR(m, y, x, indx)
INTEGER*4 m, indx(m)
COMPLEX*16 y(n), x(m)
CALL ZGTHR(m, y, x, indx)
VECLIB8:
INTEGER*8 m, indx(m)
REAL*4 y(n), x(m)
CALL SGTHR(m, y, x, indx)
INTEGER*8 m, indx(m)
REAL*8 y(n), x(m)
CALL DGTHR(m, y, x, indx)
INTEGER*8 m, indx(m), y(n), x(m)
CALL IGTHR(m, y, x, indx)
x
i
y
k
i
i 12… m.,, ,=,=