slartgs.f (3)  Linux Man Pages
NAME
slartgs.f 
SYNOPSIS
Functions/Subroutines
subroutine slartgs (X, Y, SIGMA, CS, SN)
SLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.
Function/Subroutine Documentation
subroutine slartgs (realX, realY, realSIGMA, realCS, realSN)
SLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.
Purpose:

SLARTGS generates a plane rotation designed to introduce a bulge in GolubReinschstyle implicit QR iteration for the bidiagonal SVD problem. X and Y are the toprow 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.
Parameters:

X
X is REAL The (1,1) entry of an upper bidiagonal matrix.
YY is REAL The (1,2) entry of an upper bidiagonal matrix.
SIGMASIGMA is REAL The shift.
CSCS is REAL The cosine of the rotation.
SNSN is REAL The sine of the rotation.
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Definition at line 91 of file slartgs.f.
Author
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