dlartgs - generate a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem
SUBROUTINE DLARTGS( X, Y, SIGMA, CS, SN ) DOUBLE PRECISION CS, SIGMA, SN, X, Y SUBROUTINE DLARTGS_64( X, Y, SIGMA, CS, SN ) DOUBLE PRECISION CS, SIGMA, SN, X, Y F95 INTERFACE SUBROUTINE LARTGS( X, Y, SIGMA, CS, SN ) REAL(8) :: X, Y, SIGMA, CS, SN SUBROUTINE LARTGS_64( X, Y, SIGMA, CS, SN ) REAL(8) :: X, Y, SIGMA, CS, SN C INTERFACE #include <sunperf.h> void dlartgs (double x, double y, double sigma, double *cs, double *sn); void dlartgs_64 (double x, double y, double sigma, double *cs, double *sn);
Oracle Solaris Studio Performance Library dlartgs(3P) NAME dlartgs - generate a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem SYNOPSIS SUBROUTINE DLARTGS( X, Y, SIGMA, CS, SN ) DOUBLE PRECISION CS, SIGMA, SN, X, Y SUBROUTINE DLARTGS_64( X, Y, SIGMA, CS, SN ) DOUBLE PRECISION CS, SIGMA, SN, X, Y F95 INTERFACE SUBROUTINE LARTGS( X, Y, SIGMA, CS, SN ) REAL(8) :: X, Y, SIGMA, CS, SN SUBROUTINE LARTGS_64( X, Y, SIGMA, CS, SN ) REAL(8) :: X, Y, SIGMA, CS, SN C INTERFACE #include <sunperf.h> void dlartgs (double x, double y, double sigma, double *cs, double *sn); void dlartgs_64 (double x, double y, double sigma, double *cs, double *sn); PURPOSE dlartgs generates a plane rotation designed to introduce a bulge in Golub-Reinsch-style implicit QR iteration for the bidiagonal SVD prob- lem. X and Y are the top-row entries, and SIGMA is the shift. The com- puted 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) X is DOUBLE PRECISION The (1,1) entry of an upper bidiagonal matrix. Y (input) Y is DOUBLE PRECISION The (1,2) entry of an upper bidiagonal matrix. SIGMA (input) SIGMA is DOUBLE PRECISION The shift. CS (output) CS is DOUBLE PRECISION The cosine of the rotation. SN (output) SN is DOUBLE PRECISION The sine of the rotation. 7 Nov 2015 dlartgs(3P)