subroutine crotg(ca,cb,c,s)
complex ca,cb,s
real c
real norm,scale
complex alpha
if (cabs(ca) .ne. 0.) go to 10
c = 0.
s = (1.,0.)
ca = cb
go to 20
10 continue
scale = cabs(ca) + cabs(cb)
norm = scale * sqrt((cabs(ca/scale))**2 + (cabs(cb/scale))**2)
alpha = ca /cabs(ca)
c = cabs(ca) / norm
s = alpha * conjg(cb) / norm
ca = alpha * norm
20 continue
return
end
