SLARTGS (3) - Linux Man Pages
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.
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.
X is REAL The (1,1) entry of an upper bidiagonal matrix.
Y is REAL The (1,2) entry of an upper bidiagonal matrix.
SIGMA is REAL The shift.
CS is REAL The cosine of the rotation.
SN is REAL The sine of the rotation.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
- September 2012
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