Physics data management tools: computational evolutions and benchmarks

Mincheol Han1, Chan-Hyeung Kim1, Lorenzo Moneta2, Maria Grazia Pia3, Hee Seo1

 1 Hanyang University, Korea – 2 CERN, Switzerland – 3 INFN Sezione Di Genova, Italy

SNA + MC 2010Joint International Conference on

Supercomputing in Nuclear Applications + Monte Carlo 2010

Physics data libraries

Data libraries Collection of experimental or theoretical tabulations of physics quantities e.g. cross sections, form factors, nuclear and atomic parameters etc. Distributed by data centres: RSICC (ORNL), NEA, NIST…

Essential ingredient of Monte Carlo simulation Use established data Speed up simulation w.r.t. using analytical formulae Common background for different Monte Carlo systems

ENDF/B, ENSDF, JENDL, CENDL, BROND, EEDL, EPDL, EADL…

Dealing with physics data

Data management Load (and store) data Retrieve data Use data: directly, by interpolation

Loading Usually in the simulation initialization phase Loading on demand

Retrieving In the course of the simulation (usually at each step) Can be source of significant overload

Original design in Geant4

G4EMDataSet

-z: G4int-energies: G4DataVector-data: G4DataVector-log_energies: G4DataVector-log_data: G4DataVector-algorithm: G4VDataSetAlgorithm

+FindValue()+GetComponent()+AddComponent()+NumberOfComponents()+GetEnergies()+GetData()+SetEnergiesData()+LoadData()

G4VEMDataSet

+FindValue()+GetComponent()+AddComponent()+NumberOfComponents()+GetEnergies()+GetData()+SetEnergiesData()+LoadData()

G4CompositeEMDataSet

-components: std::vector<G4VEMDataSet*>-algorithm: G4VDataSetAlgorithm

+FindValue()+GetComponent()+AddComponent()+NumberOfComponents()+GetEnergies()+GetData()+SetEnergiesData()+LoadData()-CleanUpComponents()

G4DNACrossSectionDataSet

-z: G4int-components: std::vector<G4VEMDataSet*>-algorithm: G4VDataSetAlgorithm

+FindValue()+GetComponent()+AddComponent()+NumberOfComponents()+GetEnergies()+GetData()+SetEnergiesData()+LoadData()-CleanUpComponents()

G4ShellEMDataSet

-z: G4int-components: std::vector<G4VEMDataSet*>-algorithm: G4VDataSetAlgorithm

+FindValue()+GetComponent()+AddComponent()+NumberOfComponents()+GetEnergies()+GetData()+SetEnergiesData()+LoadData()#CleanUpComponents()

G4VDataSetAlgorithm

+Calculate()+Clone()

G4LinLogInterpolation

+Calculate()+Clone()

G4LinLogLogInterpolation

+Calculate()+Clone()

G4LinInterpolation

+Calculate()+Clone()

G4SemiLogInterpolation

+Calculate()+Clone()

G4LogLogInterpolation

+Calculate()+Clone()

Composite PatternHandle different data collections transparently Data for materials Data for atoms Data for shells

Strategy PatternHandle interchangeable interpolation algorithms transparently

electromagnetic data (Livermore library)

Can we improve it?

Geant4 physics on a diet Leaner software design Improve computational performance Enhance clarity and transparency Facilitate testing Ease maintenance

CHEP 2009 R&D: physics models M.G. Pia et al., Design and performance evaluations of generic programming

techniques in a R&D prototype of Geant4 physics

Monte Carlo + CHEP 2010 R&D: physics data Prototype to evaluate candidate solutions quantitatively

This talk:selection of

preliminary results

Final and complete results will be

documented in a dedicated

publication

Test set-upTest case: Livermore library data EEDL (Evaluate Electron Data Library): ionisation, Bremsstrahlung EPDL97 (Evaluated Photon Data Library): Compton and Rayleigh

scattering, photoelectric effect, pair and triplet production EADL (Evaluated Atomic Data Library): atomic parameters

Computing environment Geant4 9.4-beta + G4EMLOW 6.13 Intel® Core™ Duo CPU E8500 with 3.16 GHz processor, 4 GB RAM,

Linux SLC5, gcc 4.3.5 compiler Intel® CPU U4100 with 1.30GHz processor, 2 GB RAM, MS Windows XP

SP3, MSVC++9 C++ compiler (with SP1)

Load test loading data for a number of elements between 1 and 100 each experiment repeated 100 times, the whole series repeated 10 times

Retrieve test finding the data associated with a randomly chosen atomic number finding procedure repeated 106 times, whole experiment repeated 10 times

Data structure

Improve the physical design of the data library itself

Large tabulations split into individual files (one per element)

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time (ms) to load data vs. number of elements present

in the experimental set-up

Excitation data

original data split data

Data structure

Large physics tabulations require large memory allocation for storing the data, time to load them into memory and to search trough them

Are all the data really necessary?

Reduce the amount of data

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A

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A

B

CSuppress B if ● can be

interpolated with the same

accuracy based on A and C

time (ms) to load data vs. number of elements present

in the experimental set-up

Compton scattering functions

Number of data for each element

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The Number of Material

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reduced

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original data reduced data

Use forthcoming C++ features

Current implementation uses STL map for most data, STL vector for a few data types

Evaluated unordered_map (AKA hash map)

Included in C++0x TR1

<tr1/unordered_map> gcc 4.3.x

<unordered_map> in MSVC

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Pair production cross sections

time (ms) to load data vs. number of elements present

in the experimental set-up

STL mapunordered_map

Caching pre-calculated data

Recent modification in Geant4 low energy electromagnetic package: cache pre-calculated log10 data

Credit to current Geant4 low energy electromagnetic group

Not to be credited to the authors of this talk

The authors of this talk Quantified the time for loading/retrieving Quantified the memory consumption

to store additional (cached) data Reviewed the modified software design

and implementation: flaws

~10% time saving w.r.t. on-the-fly log10 calculation

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retrieving

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original modified

time (ms) to load and retrieve data vs. number of elements present

in the experimental set-up

Generic programming techniques

G4EMDataSet

-Z: int-energies: vector<double>-data: vector<double>-log_energies: vector<double>-log_data: vector<double>

+GetEnergies()+GetData()+GetLogEnergies()+GetLogData()+LoadData()+SetEnergiesData()

G4GenericCrossSectionHandler

-dataMap: unordered_map<int, CONT>

+FindValue()+LoadData()

Interpmethod : typenameCONT : typenameLENGTH = 1

G4ShellEMDataSet

-Z: int-components: vector<G4EMDataSet*>

+AddComponent()+GetComponent()+GetEnergies()+GetData()+GetLogEnergies()+GetLogData()+LoadData()#CleanUpComponents()

G4SpectrumEMDataSet

-Z: int-components: vector<G4EMDataSet*>

+AddComponent()+GetComponent()+GetEnergies()+GetData()+GetLogEnergies()+GetLogData()+LoadData()#CleanUpComponents()

G4SpectrumShellEMDataSet

-Z: int-components: vector<G4ShellEMDataSet*>

+GetComponent()+GetEnergies()+GetData()+GetLogEnergies()+GetLogData()+LoadData()#CleanUpComponents()

Interpolation

+GetInterpolationValue()+GetLogEnergy()+GetLogData()

CalcEnginePolicy : typenameLin

<<CppStruct>>

+Calc()+IneedLogEnergy()+IneedLogData()

LinLog<<CppStruct>>

+Calc()+IneedLogEnergy()+IneedLogData()

SemiLog<<CppStruct>>

+Calc()+IneedLogEnergy()+IneedLogData()

LogLog<<CppStruct>>

+Calc()+IneedLogEnergy()+IneedLogData()

LinLogLog<<CppStruct>>

+Calc()+IneedLogEnergy()+IneedLogData()

polymorphic behavior of data sets and interpolation algorithms is not necessary at runtime through dynamic binding

OOAD iteration

Preliminarydesign

Templates eliminate the overhead due to the virtual table associated with inheritance

Contribution to to improving execution speed

Effect of prototype design: loading

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Bremsstrahlung cross sections

The extent of the improvement depends on the characteristics of the data

original prototype

original prototype

time (ms) to load data vs. number of elements present in the experimental set-up

Original design: STL vectors, load all elements

Effect of prototype design: retrieving

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Pair production cross sections Bremsstrahlung spectrum data

time (ms) to retrieve data vs. number of elements present in the experimental set-up

Original designPrototype design

Prototype design + unordered_map

Use vectors!

Some data sets in the original design do not require the use of STL map

Can be efficiently managed by using STL vectors

Not worthwhile to move them to unordered_map

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Original designPrototype design (map)

Prototype design (unordered_map)

ConclusionsPrototype R&D on Geant4 physics data management

Investigated Data structure Software design Use of C++0x TR1 features

Results Leaner software Improved performance

RD44 1994-1998

Geant4 R&D phaseCutting edge technologyRigorous software development process

Geant4 would profit from reenacting a R&D phase to exploit new technology

with the same spirit of scientific openness and rigorousness as RD44

Same conclusions at CHEP 2009 regarding physics modeling

AcknowledgmentThanks to CERN Directorate for support