XML Reference Guide#

This document provides a reference for the XML-based Domain Specific Language (DSL) used to define and run optimization studies in OpenPisco with the applications.

Introduction#

The primary way to interact with the OpenPisco command-line application is through an XML input file. This file defines all the components of the optimization study, including the geometry, meshes, level-sets, physical problems, optimization setup, and the sequence of actions to perform.

The root element of the file is always <data>.

<data dim="3" debug="False">
    <!-- All other tags go here -->
</data>

Root Attributes:

  • dim: The dimensionality of the problem (2 or 3).

  • debug: A boolean to enable verbose logging.

—

Core Component Tags#

The XML file is organized into several main sections, each corresponding to a core component of the OpenPisco platform. The order of these sections in the file is important, as components are often defined in terms of previously defined ones.

Zones#

The <Zones> block is used to define geometric primitives that can be combined to describe the design space, boundary condition regions, and initial shapes. Unless specified otherwise, a zone is usually an ImplicitGeometry object by the terminology of Muscat.

  • Primitives: <Plane>, <Sphere>, <Cylinder>, <Box>, etc.

  • Operators: <Union>, <Intersection>, <Difference> can be used to combine other zones.

  • `id`: Each zone is given a unique integer id so it can be referenced later.

<Zones>
    <Plane id="1" point="0.0 0.0 0.0" normal="1. 0. 0."/>
    <Sphere id="2" center="1. 0. 0." radius="0.5"/>
    <Union id="3" z="1 2" />
</Zones>

Grids#

The <Grids> block defines the computational meshes.

  • `id`: A unique integer ID for the grid.

  • ``<Grid>``: Defines a structured Cartesian grid. * n: Number of nodes in each direction (e.g., “41 41 41”). * origin: Coordinates of the grid’s origin. * length: Dimensions of the grid. * ofTetras / ofTriangles: Boolean to create a simplex-based mesh.

  • ``<Mesh>``: Loads an unstructured mesh from an external file. * filename: Path to the mesh file (e.g., .med).

<Grids>
    <Grid id="1" n="41 41 41" origin="0. 0. 0." length="2.0 0.25 1.0" ofTetras="True"/>
    <Mesh id="2" filename="path/to/my_mesh.med"/>
</Grids>

LevelSets#

The <LevelSets> block defines the level-set functions used for shape representation.

  • `id`: A unique integer ID.

  • ``<LevelSet>``: * support: The id of the <Grid> it is defined on. * conform: Boolean indicating if the mesh should be conformed to the level-set (Lagrangian/Shape Tracking approach). * <MesherInfo>: Contains parameters for the remeshing process when conform="True".

<LevelSets>
    <LevelSet id="1" support="1" conform="True">
          <MesherInfo hmax=".5" hmin="0.01" />
    </LevelSet>
</LevelSets>

PhysicalProblems#

This block defines the physical simulations to be solved (e.g., static elasticity, thermal analysis).

  • `id`: A unique integer ID.

  • ``<GeneralAster>``, ``<StaticFreeFemSolverMeca>``, etc.: The tag name corresponds to the solver type. * type: The specific analysis type (e.g., “static_elastic”). * Inner Tags: Define material properties (<Material>), boundary conditions (<Dirichlet>), and loads (<Force>).

<PhysicalProblems>
    <GeneralAster type="static_elastic" id="1" >
        <Material young="210.e9" poisson="0.3" />
        <Dirichlet eTag="X0" dofs="0 1 2" value="0.0"/>
        <Force nTag="nTag4" value="0. 0. -10000" />
    </GeneralAster>
</PhysicalProblems>

OptimProblems#

This block defines the optimization problem itself, linking together the geometry, level-set, and criteria.

  • `id`: A unique integer ID.

  • ``<OptimProblem>``: * type: The problem type, usually TopoGeneric. * useLevelset: The id of the level-set to be optimized. * OnZone: The id of the zone defining the active design space. * OffZone: The id of the zone excluded from the design space. * <Objective>: Defines the objective function.

    • type: The criterion to use (e.g., “Volume”, “Compliance”).

    • <Constraint>: Defines a constraint. * type: The criterion to use. * UpperBound / LowerBound: The constraint value. * useProblem: The id of the <PhysicalProblem> to use for criteria that need it.

<OptimProblems>
    <OptimProblem type="TopoGeneric" id="1" useLevelset="1" OnZone="8">
      <Objective type="Volume" name="Volume"/>
      <Constraint type="Compliance" name="Compliance" UpperBound="1.2" useProblem="1" />
   </OptimProblem>
</OptimProblems>

TopologicalOptimizations#

This block defines the optimization algorithm to be used.

  • `id`: A unique integer ID.

  • ``<OptimAlgoNullSpace>``, etc.: The tag name corresponds to the algorithm type. * useOptimProblem: The id of the <OptimProblem> to solve.

<TopologicalOptimizations>
    <OptimAlgoNullSpace id="1" useOptimProblem="1" />
</TopologicalOptimizations>

Actions#

The <Actions> block defines a sequence of operations to be executed. This is where the simulation is actually driven.

  • ``<Action>``: * type: The name of the action to perform (e.g., InitLevelset, RunTopoOp, SaveShapeToFile). * Attributes: Action-specific parameters. For example, RunTopoOp needs the TopoOp attribute set to the id of a <TopologicalOptimization> block.

<Actions>
    <Action type="InitLevelset" ls="1" zone="6"/>
    <Action type="RunTopoOp" TopoOp="1" />
    <Action type="SaveShapeToFile" ls="1" filename="final_shape.stl"/>
</Actions>

Outputs#

This block defines how and where to save results.

  • `id`: A unique integer ID.

  • ``<Output>``: * name: The output filename. * inTempDirectory: Boolean to save in the temporary working directory.

  • ``<Proxy>``: Can be used to combine multiple outputs.

<Outputs>
   <Output id="1" name="History.xmf" inTempDirectory="True" />
   <Output id="2" name="History.csv" inTempDirectory="True" />
   <Output id="3" name="PROXY" outputs="1 2" />
</Outputs>