1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
|
! { dg-do compile }
!
! PR fortran/48821
!
! Contributed by Daniel Carrera
!
contains
pure subroutine rk4_vec(t, Y, dY, h)
real, intent(inout) :: t, Y(:)
real, intent(in) :: h
real, dimension(size(Y)) :: k1, k2, k3, k4
interface
pure function dY(t0, y0)
import :: Y
real, intent(in) :: t0, y0(size(Y))
real :: dY(size(y0))
end function
end interface
k1 = dY(t, Y)
k2 = dY(t + h/2, Y + k1*h/2)
k3 = dY(t + h/2, Y + k2*h/2)
k4 = dY(t + h , Y + k3*h)
Y = Y + (k1 + 2*k2 + 2*k3 + k4) * h/6
t = t + h
end subroutine
end
|
