Unindented Program to be prettified using f90ppr

tridiag_unindent.f90

!--------------------------------------------------------------------------------------------------
subroutine tridiag(a, b, c, r, u, n, code)
!    Solves for a vector u of length n the tridiagonal linear set      ! from numerical recipes
!    m u = r, where a, b and c are the three main diagonals of matrix  !
!    m(n,n), the other terms are 0. r is the right side vector.        !
!--------------------------------------------------------------------------------------------------
integer, parameter               :: nmax = 100
integer, intent(in)              :: n
double precision, intent(in)     :: a(n),b(n),c(n),r(n)
double precision, intent(out)    :: u(n)
integer, intent(out)             :: code

double precision                 :: bet,gam(nmax)
integer                          :: j

if(b(1).eq.0.d0) then
code = 1                         ! error unless code=0
return
end if

bet   = b(1)
u(1 ) = r(1)/bet
do j  = 2, n                        ! decomposition and forward substitution
gam(j)  = c(j-1)/bet
bet     = b(j)-a(j)*gam(j)
if(bet .eq. 0.d0) then             ! algorithm fails
code = 2
return
end if
u(j) = (r(j)-a(j)*u(j-1))/bet
end do

do j = n-1,1,-1                     !back substitution
u(j) = u(j) - gam(j+1) * u(j+1)
end do

code = 0
return

end subroutine tridiag