ForwardEuler.hpp

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// -------------------------------------------------------//
//
// SHAMROCK code for hydrodynamics
// Copyright (c) 2021-2026 Timothée David--Cléris <tim.shamrock@proton.me>
// SPDX-License-Identifier: CeCILL Free Software License Agreement v2.1
// Shamrock is licensed under the CeCILL 2.1 License, see LICENSE for more information
//
// -------------------------------------------------------//
 
#pragma once
 
#include "shambase/SourceLocation.hpp"
#include "shambackends/kernel_call_distrib.hpp"
#include "shamcomm/logs.hpp"
#include "shamrock/solvergraph/IDataEdge.hpp"
#include "shamrock/solvergraph/IFieldSpan.hpp"
#include "shamrock/solvergraph/INode.hpp"
#include "shamrock/solvergraph/Indexes.hpp"
#include "shamsys/NodeInstance.hpp"
 
namespace shammodels::common::modules {
    template<class T>
    class ForwardEuler : public shamrock::solvergraph::INode {
 
        using Tscal = shambase::VecComponent<T>;
 
        u32 nvar;
 
        public:
        ForwardEuler(u32 nvar = 1) : nvar(nvar) {}
 
        struct Edges {
            const shamrock::solvergraph::IDataEdge<Tscal> &dt;
            const shamrock::solvergraph::IFieldSpan<T> &time_derivative;
            const shamrock::solvergraph::Indexes<u32> &sizes;
            shamrock::solvergraph::IFieldSpan<T> &field;
        };
 
        inline void set_edges(
            std::shared_ptr<shamrock::solvergraph::IDataEdge<Tscal>> dt,
            std::shared_ptr<shamrock::solvergraph::IFieldSpan<T>> time_derivative,
            std::shared_ptr<shamrock::solvergraph::Indexes<u32>> sizes,
            std::shared_ptr<shamrock::solvergraph::IFieldSpan<T>> field) {
            __internal_set_ro_edges({dt, time_derivative, sizes});
            __internal_set_rw_edges({field});
        }
 
        inline Edges get_edges() {
            return Edges{
                get_ro_edge<shamrock::solvergraph::IDataEdge<Tscal>>(0),
                get_ro_edge<shamrock::solvergraph::IFieldSpan<T>>(1),
                get_ro_edge<shamrock::solvergraph::Indexes<u32>>(2),
                get_rw_edge<shamrock::solvergraph::IFieldSpan<T>>(0)};
        }
 
        void _impl_evaluate_internal() {
 
            __shamrock_stack_entry();
 
            auto edges = get_edges();
 
            edges.field.ensure_sizes(edges.sizes.indexes);
 
            Tscal dt = edges.dt.data;
 
            if (nvar == 1) {
 
                sham::distributed_data_kernel_call(
                    shamsys::instance::get_compute_scheduler_ptr(),
                    sham::DDMultiRef{edges.time_derivative.get_spans()},
                    sham::DDMultiRef{edges.field.get_spans()},
                    edges.sizes.indexes,
                    [dt](u32 gid, const T *time_derivative, T *field) {
                        field[gid] = field[gid] + dt * time_derivative[gid];
                    });
 
            } else {
 
                auto var_count = edges.sizes.indexes.template map<u32>([&](u64 id, u32 count) {
                    return count * nvar;
                });
 
                sham::distributed_data_kernel_call(
                    shamsys::instance::get_compute_scheduler_ptr(),
                    sham::DDMultiRef{edges.time_derivative.get_spans()},
                    sham::DDMultiRef{edges.field.get_spans()},
                    var_count,
                    [dt](u32 gid, const T *time_derivative, T *field) {
                        field[gid] = field[gid] + dt * time_derivative[gid];
                    });
            }
        }
 
        inline virtual std::string _impl_get_label() const { return "ForwardEuler"; };
 
        virtual std::string _impl_get_tex() const { return "TODO"; }
    };
} // namespace shammodels::common::modules