DLARTGS (3) - Linux Man Pages
subroutine dlartgs (double precisionX, double precisionY, double precisionSIGMA, double precisionCS, double precisionSN)
DLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.
DLARTGS 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 DOUBLE PRECISION The (1,1) entry of an upper bidiagonal matrix.
Y is DOUBLE PRECISION The (1,2) entry of an upper bidiagonal matrix.
SIGMA is DOUBLE PRECISION The shift.
CS is DOUBLE PRECISION The cosine of the rotation.
SN is DOUBLE PRECISION The sine of the rotation.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
- September 2012
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