27 lines
635 B
Fortran
27 lines
635 B
Fortran
subroutine srotgf(sa,sb,c,s)
|
|
c
|
|
c construct givens plane rotation.
|
|
c jack dongarra, linpack, 3/11/78.
|
|
c
|
|
real sa,sb,c,s,roe,scale,r,z
|
|
c
|
|
roe = sb
|
|
if( abs(sa) .gt. abs(sb) ) roe = sa
|
|
scale = abs(sa) + abs(sb)
|
|
if( scale .ne. 0.0 ) go to 10
|
|
c = 1.0
|
|
s = 0.0
|
|
r = 0.0
|
|
z = 0.0
|
|
go to 20
|
|
10 r = scale*sqrt((sa/scale)**2 + (sb/scale)**2)
|
|
r = sign(1.0,roe)*r
|
|
c = sa/r
|
|
s = sb/r
|
|
z = 1.0
|
|
if( abs(sa) .gt. abs(sb) ) z = s
|
|
if( abs(sb) .ge. abs(sa) .and. c .ne. 0.0 ) z = 1.0/c
|
|
20 sa = r
|
|
sb = z
|
|
return
|
|
end
|