99 DOUBLE PRECISION cs, sigma, sn,
x, y
105 DOUBLE PRECISION negone, one, zero
106 parameter( negone = -1.0d0, one = 1.0d0, zero = 0.0d0 )
109 DOUBLE PRECISION 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
dlartgp( w, z, sn, cs, r )
subroutine dlartgp(F, G, CS, SN, R)
DLARTGP generates a plane rotation so that the diagonal is nonnegative.
subroutine dlartgs(X, Y, SIGMA, CS, SN)
DLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bid...
DOUBLE PRECISION function dlamch(CMACH)
DLAMCH