SSCTR/DSCTR/ISCTR/CSCTR/ZSCTR

Scatter sparse vector

 

indx

Array containing the indices {ki} of the interesting

 

 

elements of x. The indices must satisfy the following:

 

 

1 ≤ indx(i) ≤ n, i = 1, 2, …, m

 

 

indx(i) ≠ indx( j), 1 ≤ i ≠ j ≤ m

 

 

where n is the length of y.

Output

y

Array containing the elements of y, y(i) = yi. If m ≤ 0,

 

 

then y is unchanged. Otherwise, only the elements of y

 

 

whose indices are included in indx are changed.

Notes The result is unspecified if any element of indx is out of range, if any two elements of indx have the same value, or if x, indx, and y overlap such that any element of x or any index shares a memory location with any element of y.

Fortran Equivalent

SUBROUTINE SSCTR (M, X,INDX, Y) REAL*4 X(*),Y(*)

INTEGER*4 INDX(*)

IF ( M .LE. 0 ) RETURN DO 10 I = 1, M

Y(INDX(I)) = X(I)

10CONTINUE RETURN END

Example Scatter x into y, where x is a sparse vector with interesting elements x1, x4, x5, and x9 stored in one-dimensional array X, and y is stored in a one-dimensional array Y of dimension 20.

INTEGER*4

M,INDX(4)

REAL*8

X(4),Y(20)

DATA

INDX / 1, 4, 5, 9 /

M = 4

 

CALL DSCTR (M,X,INDX,Y)

138HP MLIB User’s Guide