Interoperable Geometry and Mesh Components for SciDAC Applications

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Terascale Simulation Tools and Technologies TSTT Omega3P (AST) p2 p5 p4 p3 pi G Mo Volume Vertex Edge Face Non-manifold topology (e.g. shared face) ILC Parameterized Geometry Virtual geometry/topology zcb zcc Procedural Geometry Generation • Device-specific function constructs geometric model from design parameter vector • Generates new geometry based on optimization-driven design parameter changes • Application of shape optimization to new device XYZ requires only new MkXYZ function Uses in Ddriv: Geometry construction function Store model to disk G(pi) pi G(pi) MkILC (Mk) Basis for mesh projection Geometric model Design parameters TSTTG/CGM (∂vΓ/∂pi) Compute design velocities r2 DDRIV Geom/mesh/smooth driver Damped De-tuned Structure International Linear Collider (ILC) G(pi)k TSTTG/MkILC construct new geom TSTTR relate geom to mesh p3 p2 p4 p1 TSTTM store mesh, derivs Mesquite smooth mesh Mk TSTTM/SIDL, TSTTM/C-Block 20 params, 525 lines C++ 15 params, 786 lines C++ MOAB/C++, TSTTM/C-Indiv MOAB/C++-Scd QVDual viz tool TSTTG Topology Non-manifold Geometry Virtual Others… ACIS Granite Facet b1l b1l b1l all all all a1l a1l a1l bll bll bll ra1 ra1 ra1 ra0 ra0 ra0 zcll zcll zcll NLC Damped De-tuned Structure (SLAC) TSTTM/SIDL Sets & tags used to store processor partition TSTTM/C MOAB/C++, CUBIT Interoperable Geometry and Mesh Components for SciDAC Applications Enabling shape optimization for future accelerator designs The Terascale Simulation Tools & Technologies (TSTT) Center SLAC/TOPS/TSTT Accelerator Shape Optimization Collaboration Purpose: Create a new generation of accelerator modeling & optimization capability from SciDAC computational components, which can be applied directly for near-term design decisions (e.g. International Linear Collider Low-Loss cavity) and to future accelerator designs (RIA, LCLS). TSTT Role: Provide advanced services for geometry (TSTTG/CGM) and mesh (TSTTM/MOAB, MESQUITE), linked to accelerator physics and optimization using core TSTT data model concepts. • Enabling access to advanced geometry & mesh representations, tools through common interfaces • MOAB (SNL): Structured/unstructured FE mesh • FMDB (RPI): Tri/tet mesh, adaptive mesh refinement • NWGrid (PNNL): Mesh generation for biological models • GRUMMP (UBC, Canada): Tri/tet mesh, mesh improvement • Mesquite (SNL): Optimization-based mesh smoothing • Frontier (BNL, SUNY-SB): (See X. Li’s poster) • Future: extension of approach to: • New components/instances of current interfaces • New domains (e.g. discretization, fields, materials, etc.) • New applications Overall Optimization Cycle: Impact: Superior accelerator cavities, yielding better accelerator performance at a lower cost mΏ(p’) DDRIV (TSTT) (p’) Procedural Geometry Generation ILC Parameterized Geometry mΏ(p) ω(p), E(d) (p), g(p) Mesh Projection/ Smoothing Design Velocities ∂vΓ/∂pi The TSTT Interfaces Omega3P Sensitivity (AST/TOPS) • TSTTR: Relations • Relates entities, sets between geometry, mesh interfaces • Dynamic mapping based on application-defined criteria • Extensible to other (e.g. hierarchical) relations δp Optimization (TOPS) depends on depends on • TSTTG: Geometry • BREP-type topological model • Sub-interfaces for: • TSTTM: Mesh • FE “zoo” + polygons, polyhedra • Entity- & array-based access • (picture of mesh…) Mesh Projection/Smoothing • Shape optimization iterations project same mesh to new geometric models • Fixed mesh topology gives continuity in optimization & allows reuse of matrix factorization in Omega3P “Design Velocity” Calculation • Design velocity = ∂xΓ/∂pi (last term in chain-rule expansion of ∂f/∂pi) • Computed AUTOMATICALLY using geometry generation function • Communicated to Omega3P as tags on surface mesh vertices CUBIT Generate mesh Go Mo Iteration 0: • Procecure: • Write original vertex positions as tag on Mk • Generate new model G(pδ) from perturbation pδ • Project/smooth mesh onto affected surfaces in G(pδ) • Compute ∂xΓ/∂pi using differencing • Store as tags on mesh vertices “implements-all” “implements-all” TSTTB: “Base” Iteration k: ∂xΓ/∂r2 • Qualitative derivative • verification using Paraview The TSTT Data Model SNL Geometry, Mesh Tools Supporting Shape Optimization • MUST be both simple AND flexible • 4 Basic Types: • Entity:topological entities in a geometry or mesh ([g]vertex, [g]edge, [g]face, [g]region) • Entity set: Arbitrary combinations of entities and of other sets; supports parent/child relations between sets (!= “contains”) • Tag: arbitrary piece of data which can be written to any of the other items; created with specified name, size, optional type; individual values assigned to any of the other items • Interface instance:instance of a component inside which entities are assumed to be related to one another, and which serves as the overall “container” of a component’s data and as the point of reference for those data Mesh-Oriented datABase (MOAB) Common Geometry Module (CGM) • High-efficiency, low memory cost implementation of full TSTTM interface • TSTTG implementation: representation, modification of solid model-based geometry Full TSTTG Interface • Structured & unstructured mesh • FE “zoo” + polygons, polyhedra • Reads and/or writes CUBIT .cub files (w/metadata), ExoII, vtk, etc. • Geom topology as sets w/parent-child relations • Various other tools • Converter (ExoII, vtk, .cub, Ansys, …) • Viz (Qt-, VTK-based) • Available under LGPL license(http://cubit.sandia.gov/MOAB) • C-based TSTTM interface implementation available too } Layered implementation for applicability across engines CAD-, facet- based engines Access times comparable to object-based C++ ARIES Compact Stellerator Tags on vertices used to communicate surface normals to Mesquite, Omega3P • Memory efficient: • 25MB/106 hex elements (structured) • 55MB/106 hex elements (unstructured”) • CGM is the basis for SNL’s CUBIT mesh generation tool • LGPL release summer ’05(http://cubit.sandia.gov/MOAB) ITER “Simplified” Benchmark Model LASSO (TSTTR) Mesh Quality Improvement Toolkit (MESQUITE) • Restore, evaluate data relations between interacting components • Why not bundle components together? Because smaller components: • Promote re-usability • Reduce complexity • Give applications options/flexibility • Then why is TSTTR necessary?Because advanced applications require interactions between components • Geometry-mesh • Geometry-materials • Fields-mesh Set parent-child relations show geometric model topology • Optimization-based mesh smoothing software library • Structured, unstructured, hybrid meshes (most element types) • Multiple state-of-the-art algorithms and solvers • Multiple application domains: • Deforming domains/meshes, • r-type adaptivity • Heterogeneous, anisotropic mesh smoothing • Arbitrary-Lagrange-Eulerian mesh smoothing • Mesh fixup (untangle, shape, smoothness) • Released under LGPL license (http://www.cs.sandia.gov/~web9200/) Shape Optimization Shape Optimization Design Viz TSTTR/ LASSO TSTTG/CGM TSTTM/ MOAB