NAME¶

ZROTG - construct givens plane rotation

SYNOPSIS¶

subroutine zrotg(ca,cb,c,s)

double

complex ca,cb,s

double

precision c

double

precision norm,scale

double

complex alpha

if

(cdabs(ca) .ne. 0.0d0) go to 10

c

= 0.0d0

s

= (1.0d0,0.0d0)

ca

= cb

go

to 20

10

continue

scale

= cdabs(ca) + cdabs(cb)

norm

= scale*dsqrt((cdabs(ca/dcmplx(scale,0.0d0)))**2 +

*

(cdabs(cb/dcmplx(scale,0.0d0)))**2)

alpha

= ca /cdabs(ca)

c

= cdabs(ca) / norm

s

= alpha * dconjg(cb) / norm

ca

= alpha * norm

20

continue

return

end

PURPOSE¶