Provided by: liblapack-doc_3.3.1-1_all

**NAME**

LAPACK-3 - generates a plane rotation designed to introduce a bulge in Golub-Reinsch-style implicit QR iteration for the bidiagonal SVD problem

**SYNOPSIS**

SUBROUTINE SLARTGS( X, Y, SIGMA, CS, SN ) IMPLICIT NONE REAL CS, SIGMA, SN, X, Y

**PURPOSE**

SLARTGS generates a plane rotation designed to introduce a bulge in Golub-Reinsch-style implicit QR iteration for the bidiagonal SVD problem. X and Y are the top-row entries, and SIGMA is the shift. The computed CS and SN define a plane rotation satisfying [ CS SN ] . [ X^2 - SIGMA ] = [ R ], [ -SN CS ] [ X * Y ] [ 0 ] with R nonnegative. If X^2 - SIGMA and X * Y are 0, then the rotation is by PI/2.

**ARGUMENTS**

X (input) REAL The (1,1) entry of an upper bidiagonal matrix. Y (input) REAL The (1,2) entry of an upper bidiagonal matrix. SIGMA (input) REAL The shift. CS (output) REAL The cosine of the rotation. SN (output) REAL The sine of the rotation. LAPACK routine (version 3.3.0) April 2011 SLARTGS(3lapack)