dlartgp.f (3)

Functions/Subroutines

subroutine dlartgp (F, G, CS, SN, R)

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

subroutine dlartgp (double precisionF, double precisionG, double precisionCS, double precisionSN, double precisionR)

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.

Date:

September 2012

Definition at line 96 of file dlartgp.f.

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