Code Design

Code Design#

Mixin and Composition#

Elastica package follows Mixin and composition design patterns that may be unfamiliar to users. Here is a collection of references that introduce the package design.

References#

Structural subtyping#

Elastica package uses structural subtyping to allow users to define their own classes and functions. Here is a typing.Protocol structure that is used in the package.

Systems#

            flowchart LR
      direction RL
      subgraph Systems Protocol
        direction RL
        SymST["SymplecticSystemProtocol<br/>(Mixin for timestepper)<br/>• update_kinematics<br/>• update_dynamics"]
        style SymST text-align:left
        StaticSystemType["Static System Type"<br/>• Plane]
        SystemType["(Dynamic) System Type<br/>• CosseratRod (Rod)<br/>• Sphere (RigidBody)<br/>• Cylinder (RigidBody)"]

        SystemType --> SymST
      end

      subgraph System Collection
        SysColl["SystemCollectionProtocol"]
      end

      subgraph Timestepper Protocol
        direction LR
        SymplecticStepperProtocol["SymplecticStepperProtocol<br/>• PositionVerlet"]
        style SymplecticStepperProtocol text-align:left
      end

      SymST --> SysColl -->|Symplectic systems only| SymplecticStepperProtocol
      StaticSystemType --> SysColl

Key takeaways:#

  • Any object that conforms to StaticSystemProtocol can be added to the system collection.

    • If you want to add custom type to the system, you can use append_allowed_types to add it to the system collection. To add associated block support, you can use enable_block_supports.

  • Among the systems added to the system collection, only objects that conform to SymplecticSystemProtocol will be integrated by the symplectic timestepper. This protocol requires update_kinematics(time, prefac) and update_dynamics(time, prefac) methods to be implemented.

  • If block support is available for a system, they will be collected together during the finalize step, and passed to the timestepper.

System Collection (Build memory block)#

            flowchart LR
      Sys((Systems))
      St((Stepper))
      subgraph SystemCollectionType
        direction LR
        StSys["StaticSystem:<br/>• Plane"]
        style StSys text-align:left
        DynSys["DynamicSystem:<br/>• CosseratRod<br/>• Sphere<br/>• Cylinder"]
        style DynSys text-align:left

        BlDynSys["BlockSystem:<br/>• MemoryBlockCosseratRod<br/>• MemoryBlockRigidBody"]
        style BlDynSys text-align:left

        F{{"Feature Group (OperatorGroup):<br/>• Synchronize<br/>• Constrain values<br/>• Constrain rates<br/>• Callback"}}
        style F text-align:left
      end
      Sys --> StSys --> F
      Sys --> DynSys -->|Finalize| BlDynSys --> St
      DynSys --> F <--> St

System Collection (Features)#

            flowchart LR
      Sys((Systems))
      St((Stepper))
      subgraph SystemCollectionType
        direction LR
        StSys["StaticSystem:<br/>• Plane"]
        style StSys text-align:left
        DynSys["DynamicSystem:<br/>• Rod<br/>&nbsp;&nbsp;• CosseratRod<br/>• RigidBody<br/>&nbsp;&nbsp;• Sphere<br/>&nbsp;&nbsp;• Cylinder"]
        style DynSys text-align:left

        subgraph Feature
        direction LR
        Forcing -->|add_forcing_to| Synchronize
        Constraints -->|constrain| ConstrainValues
        Constraints -->|constrain| ConstrainRates
        Contact -->|detect_contact_between| Synchronize
        Connection -->|connect| Synchronize
        Damping -->|dampen| ConstrainRates
        Callback -->|collect_diagnostics| CallbackGroup
        end
      end
      Sys --> StSys --> Feature
      Sys --> DynSys
      DynSys --> Feature <--> St
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