STATUS OF THE UNIFIED SOLIDS LIBRARYGabriele Cosmo/CERN

Tatiana Nikitina/CERN

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Motivations for a common solids library

• Optimize and guarantee better long-term maintenance of ROOT and Geant4 solids libraries

• Create a single high quality library to replace solid libraries in Geant4 and ROOT

• Starting from what exists today in Geant4 and ROOT• Adopt a single type for each shape• Significantly optimize (Multi-Union, Tessellated Solid, Polyhedra,

Polycone)• Reach complete conformance to GDML solids schema

• Create extensive testing suite

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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Solids implemented so far• Box• Orb• Trapezoid• Sphere (+ sphere section)• Tube (+ cylindrical section) • Cone (+ conical section) • Generic trapezoid• Tetrahedron• Arbitrary Trapezoid (ongoing)• Multi-Union• Tessellated Solid• Polycone• Polyhedra• Extruded solid (ongoing)

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Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

Polycone

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New Ordinary Polycone• Special optimization for common cases, where Z

sections can only increase (big majority of real cases)• New implementation based on composition of separate

instances of cones, tubes (or their sections)• With spatial optimisation over Z• Helping for more readable, more compact and faster code• Excellent scalability over the number of Z sections• Significant performance improvement

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Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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Ordinary Polycone performance3 Z-sections• Speedup factor 3.3x vs. Geant4, 7.6x vs. ROOT for most

performance critical methods, i.e.:

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Performance of methods at folder polycone-3s-360-perf

Geant4

ROOTUSolids

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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Ordinary Polycone performance10 z sections • Speedup factor 8.3x vs. Geant4, 7.9x vs. ROOT for most

performance critical methods

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Performance of methods at folder polycone-10s-360-perf

Geant4

ROOTUSolids

NOTE: Geant4 poor performance scalability (high number of Z sections) due to absence of spatial optimization

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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Generic Polycone• Case in which either the outer or the inner surface has

more than one cone or tube section over a finite interval of Z values• Using voxelization on generalized surface

facet model• Performance improvement over Geant4

(generic polycone exists only in Geant4)• Performance improvement depends on the

number of sections and is slightly worse than in case of ordinary polycone

• Scalability is as excellent as for the ordinary polycone case

• Tested and measured on original Geant4 test cases of solids

• Values are 100% numerically coincident with Geant4

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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Ordinary vs. Generic Polycone

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Geant4 Polycone

New Generic PolyconeNew Ordinary Polycone

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Geant4 Polycone

New Generic PolyconeNew Ordinary Polycone

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Performance of method DistanceToIn at folder combined

Geant4 Polycone

New Generic PolyconeNew Ordinary Polycone

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Geant4 Polycone

New Generic PolyconeNew Ordinary Polycone

NOTE: Geant4 poor performance scalability (high number of Z sections) due to absence of spatial optimization

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

Polyhedra

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New Polyhedra implementation• Similar methodology adopted as for the

Generic Polycone• Spatial optimisation for Z sections• Works for both ordinary and generic polyhedra• Provides improvement of performance and scalability

• Values are 100% numerical coincident with Geant4

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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Example: DistanceToIn() scalability

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Performance of method DistanceToIn at folder log

Geant4

ROOTUSolid

NOTE: Geant4 poor performance scalability (high number of Z sections) due to absence of spatial optimization

Similar figures for the other key functions

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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Arbitrary Trap• Implemented first version of Arbitrary Trap• Optimization is done for main methods

• Still some methods to optimise:

SurfaceNormal(), SafetyFromInside()

Performance for UGenericTrap with twist

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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Extruded Solid• Implemented first version of ExtrudedSolid

based on TessellatedSolid• Scalability studies show that this shape can

be more optimized. Work in progress…

Scalability for DistanceToOut() in UExtrudedSolid

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

Current Status & Plans

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Status of USolids library• Review of secondary functions and tools for all implemented

primitives has been completed• Library in the current form (excluding few primitives) distributed

as optional module in latest Geant4 release 10.0• Expecting a lot of useful feedback !• Validation of available shapes on realistic detector geometries is ongoing

• Testing suite further extended for performance measurements and exact comparisons to Geant4 and ROOT

• Code available in the AIDA SVN repository• Using standard AIDA CMake setup for build/installation

• Documentation available from AIDA WP2 web• http://aidasoft.web.cern.ch/USolids

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

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USolids plan of work• Short term (by end 2014)

• Complete implementation for missing shapes• Cut Tube, Torus, Ellipsoid, Hypeboloid, Paraboloid, Elliptical Tube,

Elliptical Cone

• Provide ability to perform Boolean operations• Simple Union, Subtraction, Intersection

• Medium/Long term (AIDA2 proposal)• Extend signatures of classes to enable use of vectorisation

• SIMD instructions

• Review algorithms on all developed shapes to efficiently apply vectorisation and strong code specialization• Define proper interfaces for use in Geant4, ROOT and Vector prototype

Thursday, 27 March 2014 AIDA 3rd Annual Meeting - WP2 / Status of the Unified Solids Library

Thanks