RungeKutta_step.F90

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!! NOTICE
!!  Copyright 2022 UChicago Argonne, LLC and contributors
!!
!!  Licensed under the Apache License, Version 2.0 (the "License");
!!  you may not use this file except in compliance with the License.
!!
!!  Unless required by applicable law or agreed to in writing, software
!!  distributed under the License is distributed on an "AS IS" BASIS,
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!!  See the License for the specific language governing permissions and
!!  limitations under the License.
!!
 
subroutine RungeKutta_step (method,                      &
                            f, x, y,                     &
                            eFrac, eBase,                &
                            htry,                        &
                                           hused, hnext, &
                                           yout, eout    )
 
  implicit none
 
  interface
    function f (x,y)
      real, intent (in) :: x
      real, intent (in) :: y (:)
      real              :: f (1:size (y))
    end function f
  end interface
 
  character (len=*), intent (in)  :: method
  real,              intent (in)  :: x
  real,              intent (in)  :: y     (:)
  real,              intent (in)  :: eFrac
  real,              intent (in)  :: eBase (:)
  real,              intent (in)  :: htry
  real,              intent (out) :: hused
  real,              intent (out) :: hnext
  real,              intent (out) :: yout  (:)
  real,              intent (out) :: eout  (:)
 
  hused = 0.0
  hnext = 0.0
 
  yout(:) = 0.0
  eout(:) = 0.0
 
  return
end subroutine RungeKutta_step