91 SUBROUTINE slartgs( X, Y, SIGMA, CS, SN )
99 REAL CS, SIGMA, SN, X, Y
105 REAL NEGONE, ONE, ZERO
106 parameter ( negone = -1.0e0, one = 1.0e0, zero = 0.0e0 )
109 REAL R, S, THRESH, W, Z
121 IF( (sigma .EQ. zero .AND. abs(x) .LT. thresh) .OR.
122 $ (abs(x) .EQ. sigma .AND. y .EQ. zero) )
THEN
125 ELSE IF( sigma .EQ. zero )
THEN
126 IF( x .GE. zero )
THEN
133 ELSE IF( abs(x) .LT. thresh )
THEN
137 IF( x .GE. zero )
THEN
142 z = s * (abs(x)-sigma) * (s+sigma/x)
151 CALL slartgp( w, z, sn, cs, r )
subroutine slartgp(F, G, CS, SN, R)
SLARTGP generates a plane rotation so that the diagonal is nonnegative.
subroutine slartgs(X, Y, SIGMA, CS, SN)
SLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bid...