NAME

lartgp - lartgp: generate plane rotation, more accurate than BLAS rot

SYNOPSIS

Functions

subroutine dlartgp (f, g, cs, sn, r)
DLARTGP generates a plane rotation so that the diagonal is nonnegative. subroutine slartgp (f, g, cs, sn, r)
SLARTGP generates a plane rotation so that the diagonal is nonnegative.

Detailed Description

Function Documentation

subroutine dlartgp (double precision f, double precision g, double precision cs, double precision sn, double precision r)

DLARTGP generates a plane rotation so that the diagonal is nonnegative.

Purpose:



 DLARTGP generates a plane rotation so that


    [  CS  SN  ]  .  [ F ]  =  [ R ]   where CS**2 + SN**2 = 1.


    [ -SN  CS  ]     [ G ]     [ 0 ]


 This is a slower, more accurate version of the Level 1 BLAS routine DROTG,


 with the following other differences:


    F and G are unchanged on return.


    If G=0, then CS=(+/-)1 and SN=0.


    If F=0 and (G .ne. 0), then CS=0 and SN=(+/-)1.


 The sign is chosen so that R >= 0.

Parameters



          F is DOUBLE PRECISION


          The first component of vector to be rotated.



          G is DOUBLE PRECISION


          The second component of vector to be rotated.



          CS is DOUBLE PRECISION


          The cosine of the rotation.



          SN is DOUBLE PRECISION


          The sine of the rotation.



          R is DOUBLE PRECISION


          The nonzero component of the rotated vector.


  This version has a few statements commented out for thread safety


  (machine parameters are computed on each entry). 10 feb 03, SJH.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 94 of file dlartgp.f.

subroutine slartgp (real f, real g, real cs, real sn, real r)

SLARTGP generates a plane rotation so that the diagonal is nonnegative.