mat_rrotg Subroutine

subroutine mat_rrotg(da,db,c,s)

! ident_48="@(#)M_LA::mat_rrotg(3fp): construct Givens plane rotation."

doubleprecision :: da
doubleprecision :: db
doubleprecision :: c
doubleprecision :: s

doubleprecision :: rho
doubleprecision :: r
doubleprecision :: z

   rho = db
   if ( dabs(da) .gt. dabs(db) ) rho = da
   c = 1.0d0
   s = 0.0d0
   z = 1.0d0
   r = mat_flop(dsign(mat_pythag(da,db),rho))
   if (r .ne. 0.0d0) c = mat_flop(da/r)
   if (r .ne. 0.0d0) s = mat_flop(db/r)
   if ( dabs(da) .gt. dabs(db) ) z = s
   if (dabs(db) .ge. dabs(da) .and. c .ne. 0.0d0)z = mat_flop(1.0d0/c)
   da = r
   db = z
end subroutine mat_rrotg