lartgp - Man Page

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.

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

          F is DOUBLE PRECISION
          The first component of vector to be rotated.

G

          G is DOUBLE PRECISION
          The second component of vector to be rotated.

CS

          CS is DOUBLE PRECISION
          The cosine of the rotation.

SN

          SN is DOUBLE PRECISION
          The sine of the rotation.

R

          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.

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

Purpose:

 SLARTGP 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 SROTG,
 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

          F is REAL
          The first component of vector to be rotated.

G

          G is REAL
          The second component of vector to be rotated.

CS

          CS is REAL
          The cosine of the rotation.

SN

          SN is REAL
          The sine of the rotation.

R

          R is REAL
          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 slartgp.f.