!-----------------------------------------------------------------------------------------------------------------------------------
! This file is part of ReMKiT1D.
!
! ReMKiT1D is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as
! published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
!
! ReMKiT1D is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
!
! You should have received a copy of the GNU General Public License along with ReMKiT1D. If not, see <https://www.gnu.org/licenses/>.
!
! Copyright 2023 United Kingdom Atomic Energy Authority (stefan.mijin@ukaea.uk)
!-----------------------------------------------------------------------------------------------------------------------------------
module explicit_rk_integrator_class
!! author: Stefan Mijin
!!
!! Contains an explicit Runge-Kutta integrator class with the option to supply user Butcher tableaus
use data_kinds ,only: rk ,ik
use god_objects ,only: Object
use runtime_constants ,only: debugging, assertions, assertionLvl
use assertion_utility ,only: assert, assertIdentical, assertPure
use modeller_surrogate_class ,only: ModellerSurrogate
use variable_container_class ,only: VariableContainer
use modeller_class ,only: Modeller
use integrator_abstract_class ,only: Integrator
use support_types ,only: IntArray ,RealArray ,LogicalArray
use mpi_controller_class ,only: CommunicationData
use timestep_controller_abstract_class ,only: TimestepController
implicit none
private
type ,public :: BTableau
!! Butcher tableau derived type
type(RealArray) ,allocatable ,dimension(:) ,public :: a !! Lower triangular matrix of coefficients
real(rk) ,allocatable ,dimension(:) ,public :: b !! Coefficients for summing over intermediate values
real(rk) ,allocatable ,dimension(:) ,public :: c !! Time coefficients
end type
type ,public ,extends(Integrator) :: ExplicitRKIntegrator
!! Explicit Runge-Kutta integrator
type(BTableau) ,private :: tableau !! Butcher tableau used by the integrator
type(IntArray) ,allocatable ,dimension(:) ,private :: tableauANonzeros !! Locations of non-zeros in the a_ij tableau matrix
type(RealArray) ,allocatable ,dimension(:,:) ,private :: intermediateValues !! Buffer for intermediate RK values for various variables
type(VariableContainer) ,allocatable ,private :: buffer !! VariableContainer buffer for passing to Modeller routines
contains
procedure ,public :: affect => integrateRK
procedure ,public :: init => initRKIntegrator
end type ExplicitRKIntegrator
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interface
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module subroutine integrateRK(this,manipulatedModeller,outputVars,inputVars)
!! Implementation of abstract manipulate routine for the case of Runge-Kutta integrator
class(ExplicitRKIntegrator) ,intent(inout) :: this
class(ModellerSurrogate) ,intent(inout) :: manipulatedModeller !! Modeller to be used in callbacks during integration
class(VariableContainer) ,intent(inout) :: outputVars !! VariableContainer object to store the integration output
class(VariableContainer) ,intent(in) :: inputVars !! VariableContainer object housing input data for the integration routine
end subroutine integrateRK
!-----------------------------------------------------------------------------------------------------------------------------------
module subroutine initRKIntegrator(this,modelList,termGroups,order,tableau,evolvesTimeVar,dtController,initialTimestep)
!! Constructs an RK integrator with initial evaluated model indices and correspoding term groups if those
!! are present. If neither order or tableau are provided defaults to forward Euler time-stepping. Possible order values are 1,2,3,4
!! where 2 is the midpoint method, 3 is SSPRK3, and 4 is the standard RK4 method.
implicit none
class(ExplicitRKIntegrator) ,intent(inout) :: this
integer(ik) ,optional ,dimension(:) ,intent(in) :: modelList !! List of models this integrator will be responsible for
type(IntArray) ,optional ,dimension(:) ,intent(in) :: termGroups !! Term groups this integrator is responsible for - should conform with modelList
integer(ik) ,optional ,intent(in) :: order !! Runge-Kutta order
type(BTableau) ,optional ,intent(in) :: tableau !! User-defined Butcher tableau
logical ,optional ,intent(in) :: evolvesTimeVar !! Set to true if this integrator is allowed to change the "time" varible (if present in passed variable container)
class(TimestepController) ,optional ,intent(in) :: dtController !! User-supplied timestep controller object
real(rk) ,optional ,intent(in) :: initialTimestep !! Default timestep
end subroutine initRKIntegrator
!-----------------------------------------------------------------------------------------------------------------------------------
end interface
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end module explicit_rk_integrator_class
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