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