Pass fluxes to elliptic source computers #2553
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@@ -43,34 +43,44 @@ struct FirstOrderFluxesImpl<Dim, tmpl::list<PrimalFields...>, | |
| } | ||
| }; | ||
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| template <size_t Dim, typename PrimalFields, typename AuxiliaryFields, | ||
| typename SourcesComputer> | ||
| struct FirstOrderSourcesImpl; | ||
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| template <size_t Dim, typename... PrimalFields, typename... AuxiliaryFields, | ||
| typename SourcesComputer> | ||
| struct FirstOrderSourcesImpl<Dim, tmpl::list<PrimalFields...>, | ||
| tmpl::list<AuxiliaryFields...>, SourcesComputer> { | ||
| template <typename VarsTags, typename... SourcesArgs> | ||
| static constexpr void apply( | ||
| const gsl::not_null< | ||
| Variables<db::wrap_tags_in<::Tags::Source, VarsTags>>*> | ||
| sources, | ||
| const Variables<VarsTags>& vars, | ||
| const Variables<db::wrap_tags_in< | ||
| ::Tags::Flux, VarsTags, tmpl::size_t<Dim>, Frame::Inertial>>& fluxes, | ||
| const SourcesArgs&... sources_args) noexcept { | ||
| // Set auxiliary field sources to the auxiliary field values to begin with. | ||
| // This is the standard choice, since the auxiliary equations define the | ||
| // auxiliary variables. Source computers can adjust or add to these sources. | ||
| tmpl::for_each<tmpl::list<AuxiliaryFields...>>( | ||
| [&sources, &vars](const auto auxiliary_field_tag_v) noexcept { | ||
| using auxiliary_field_tag = | ||
| tmpl::type_from<decltype(auxiliary_field_tag_v)>; | ||
| get<::Tags::Source<auxiliary_field_tag>>(*sources) = | ||
| get<auxiliary_field_tag>(vars); | ||
| }); | ||
| // Call into the sources computer to set primal field sources and possibly | ||
| // adjust auxiliary field sources. The sources depend on the primal and the | ||
| // auxiliary variables. However, we pass the volume fluxes instead of the | ||
| // auxiliary variables to the source computer as an optimization so they | ||
| // don't have to be re-computed. | ||
| SourcesComputer::apply( | ||
| make_not_null(&get<::Tags::Source<PrimalFields>>(*sources))..., | ||
| make_not_null(&get<::Tags::Source<AuxiliaryFields>>(*sources))..., | ||
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There was a problem hiding this comment. You keep saying "instead of the auxiliary fields" but here you pass the aux fields. Please correct this There was a problem hiding this comment. No this passes the sources for the auxiliary fields so terms can be added to them, such as Christoffel symbol terms (see this comment #2553 (comment)). Does that make sense? There was a problem hiding this comment. Okay, that makes sense. I still don't understand why you say "instead of" because the code didn't previously pass the aux vars. Why wouldn't you need the aux vars (I realize they weren't passed before)? Is that because technically they are just (roughly) the derivatives of the primal fields? If so, I'm a bit confused that stability and well-posedness aren't adversely affected by never using the aux variables, though explaining that is beyond the scope of a GitHub comment, I think ;) There was a problem hiding this comment. Previously I didn't pass In the comments I say "instead of" because the sources are a function of the variables (primal and auxiliary), but instead of the aux vars I pass the primal fluxes as an optimization, as we discussed before. Does this clear things up? There was a problem hiding this comment. Yes, but I think this lengthy discussion suggests that you should either remove the There was a problem hiding this comment. Adjusted the commit message and the code comment in the fixup commit, please take a look. |
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| sources_args..., get<PrimalFields>(vars)..., | ||
| get<::Tags::Flux<PrimalFields, tmpl::size_t<Dim>, Frame::Inertial>>( | ||
| fluxes)...); | ||
| } | ||
| }; | ||
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@@ -118,30 +128,41 @@ auto first_order_fluxes(const Variables<VarsTags>& vars, | |
| * \brief Compute the sources \f$S(u)\f$ for the first-order formulation of | ||
| * elliptic systems. | ||
| * | ||
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There was a problem hiding this comment. add a discussion as to why the sources terms are getting the fluxes |
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| * This function takes the `fluxes` as an argument in addition to the variables | ||
| * as an optimization. The fluxes will generally be computed before the sources | ||
| * anyway, so we pass them to the source computers to avoid having to re-compute | ||
| * them for source-terms that have the same form as the fluxes. | ||
| * | ||
| * \see `elliptic::first_order_operator` | ||
| */ | ||
| template <size_t Dim, typename PrimalFields, typename AuxiliaryFields, | ||
| typename SourcesComputer, typename VarsTags, typename... SourcesArgs> | ||
| void first_order_sources( | ||
| gsl::not_null<Variables<db::wrap_tags_in<::Tags::Source, VarsTags>>*> | ||
| sources, | ||
| const Variables<VarsTags>& vars, | ||
| const Variables<db::wrap_tags_in<::Tags::Flux, VarsTags, tmpl::size_t<Dim>, | ||
| Frame::Inertial>>& fluxes, | ||
| const SourcesArgs&... sources_args) noexcept { | ||
| first_order_operator_detail::FirstOrderSourcesImpl< | ||
| Dim, PrimalFields, AuxiliaryFields, | ||
| SourcesComputer>::apply(std::move(sources), vars, fluxes, | ||
| sources_args...); | ||
| } | ||
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| template <size_t Dim, typename PrimalFields, typename AuxiliaryFields, | ||
| typename SourcesComputer, typename VarsTags, typename... SourcesArgs> | ||
| auto first_order_sources( | ||
| const Variables<VarsTags>& vars, | ||
| const Variables<db::wrap_tags_in<::Tags::Flux, VarsTags, tmpl::size_t<Dim>, | ||
| Frame::Inertial>>& fluxes, | ||
| const SourcesArgs&... sources_args) noexcept { | ||
| Variables<db::wrap_tags_in<::Tags::Source, VarsTags>> sources{ | ||
| vars.number_of_grid_points()}; | ||
| first_order_operator_detail::FirstOrderSourcesImpl< | ||
| Dim, PrimalFields, AuxiliaryFields, | ||
| SourcesComputer>::apply(make_not_null(&sources), vars, fluxes, | ||
| sources_args...); | ||
| return sources; | ||
| } | ||
| // @} | ||
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The commit message is incorrect. The systems don't need the fluxes to compute sources, but that having access to the fluxes is an optimization.