F_SGEN_JROT/F_DGEN_JROT/F_CGEN_JROT/F_ZGEN_JROT

Generate Jacobi rotation

Name F_SGEN_JROT/F_DGEN_JROT/F_CGEN_JROT/F_ZGEN_JROT Generate Jacobi rotation

Purpose

F_xGEN_JROT constructs a Jacobi rotation so that (a, b, c, s) ← jrot( x, y, z)

 

 

a 0

 

=

 

c s

 

•

 

x y

 

•

 

c –s

 

 

 

 

 

 

 

 

 

 

 

 

0 b

 

 

 

–s c

 

 

 

y

z

 

 

 

s c

 

Input the JROT parameter to specify whether the rotation generated is outer, inner, or sorted.

•If JROT = BLAS_INNER_ROTATION

then the rotation is chosen so that

1

c ≥ ------

 

2

•If JROT = BLAS_OUTER_ROTATION

then the rotation is chosen so that

1

0 ≤ c ≤ ------

 

2

•If JROT = BLAS_SORTED_ROTATION

then the rotation is chosen so that abs(a) ≥ abs(b)

Usage VECLIB:

INTEGER*4 JROT

REAL*4S, X, Y, Z, C

SUBROUTINE F_SGEN_JROT (JROT, X, Y, Z, C, S)

INTEGER*4 JROT

REAL*8S, X, Y, Z, C

SUBROUTINE F_DGEN_JROT (JROT, X, Y, Z, C, S)

INTEGER*4

JROT

REAL*4

X, Z, C

COMPLEX*8

S, Y

SUBROUTINE F_CGEN_JROT (JROT, X, Y, Z, C, S)

INTEGER*4

JROT

REAL*8

X, Z, C

COMPLEX*16

S, Y

SUBROUTINE F_ZGEN_JROT (JROT, X, Y, Z, C, S)

VECLIB8:

178HP MLIB User’s Guide