SSYR2/DSYR2/CHER2/ZHER2

Rank-2 update

incy = 0

Actual character arguments in a subroutine call can be longer than the corresponding dummy arguments. Therefore, readability of the CALL statement may be improved by coding the uplo argument as ’LOWER’ for ’L’ or ’UPPER’ for ’U’.

Example 1 Apply a REAL*4 symmetric rank-2 update xyT+xTy to A, where A is a 9-by-9 real symmetric matrix whose upper triangle is stored in the upper triangle of an array A whose dimensions are 10-by-10, x is a real vector 9 elements long stored in an array X of dimension 10, and y is a real vector 9 elements long stored in an array Y also of dimension 10.

CHARACTER*1 UPLO

INTEGER*4 N,LDA,INCX,INCY

REAL*4 ALPHA,A(10,10),X(10),Y(10)

UPLO = ’U’

N = 9

ALPHA = 1.0

LDA = 10

INCX = 1

INCY = 1

CALL SSYR2 (UPLO,N,ALPHA,X,INCX,Y,INCY,A,LDA)

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