The Flash Code

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The Flash Code
From Design to Applications
From Applications to Design

• Tomek Plewa
• on behalf of almost countless contributors
• The ASCI Flash Center
• Dept. of Astronomy Astrophysics
• The University of Chicago
• July 22, 2002

http//flash.uchicago.edu
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What Is the Flash Center?

• Supported by the DOE ASCI/Alliances Program

• Over 1,000,000 p.a. budget
• 20 core researches, 30 contributors at different
  levels
• Access to the most advanced computer technology

• Close partners at UofC, ANL MCS, UCSC, UIUC
• Collaboration with LLNL, LANL, LBNL, Sandia, ORNL
• Links to MPA Garching, Arizona, Palermo, Torino

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What Is the FLASH Code?

• Has a modern architecture
• modular with interfaces
• configurable with parameter/variable database

• Is highly portable
• across software platforms most UNICES including
  Linux
• across hardware platforms MPI for intra- and
  inter-box communication
• scalar cache-based systems
• provides strong tests of software (operating
  system, compiler,
• language interoperability) and hardware
  (network, storage)
• parallel I/O with HDF5 for large data sets

• Can solve a broad range of problems
• adaptive mesh discretization in 3-D with
  PARAMESH, compressible hydrodynamics,
• MHD, SRHD, elliptic operators, explicit
  diffusion, complex EOS, particle tracking

• Future developments
• extended framework through IBEAM (parallel
  solvers for large linear systems)
• formal interface specification (for solvers and
  mesh component)
• front tracking component
• elements of TSTT/CCA forums
• interoperability with other AMR software

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Primary Applications

• X-ray bursts on neutron star surfaces
• Novae
• Type Ia supernovae

• The common elements
• The underlying stars are compact
• Members of close binary systems
• Physical processes hydrodynamics, complex EOS,
  gravitation, nuclear burning
• Radiation hydrodynamics important at late times
• Initial conditions involve long timescales
  (implicit solve)
• Rapid evolution during final event (explicit
  solve)

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Primary Applications Towards Understanding

• What is environment for the explosion?
• How does it form?
• What happens during the explosion?
• Where are complex elements produced?
• How big is the Universe?
• How old is the Universe?

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Primary Applications Examples
Flame-vortex interactions
R-M instability
Laser-driven shock instabilities
Wave breaking on white dwarfs
Cellular detonation
Helium burning on neutron stars
Magnetic and hydrodynamic Rayleigh-Taylor
instabilities
Type Ia supernova
Landau-Darrieus instability
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Primary Applications Examples
Wave breaking on white dwarfs
3-D Rayleigh-Taylor instability
Flame-vortex interactions
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Additional Applications
Jeans instability
Intracluster interactions
Non-relativistic accretion onto BH
Relativistic accretion onto NS
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The FLASH 2 Code at a Glance

• General description
• parallel block-structured adaptive mesh
  refinement code
• Solvers constantly developed
• hyperbolic hydrodynamics, MHD, and SRHD
• elliptic self-gravity
• parabolic thermal conduction
• ODE nuclear burning
• Architecture undergoes substantial changes
• modular, fine-grained, SPMD (patch-based),
  efficient parallelism
• cache-based scalar architectures (most of the
  market)
• mostly F90 with elements in C no language
  restrictions
• Testing one of the finest and most matured
  elements
• used to control development and prevent major
  design flaws
• compile ? run ? compare
• applied daily on several platforms, centralized
  database

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The FLASH 2 Code Physics Modules

• Compressible hydro
• PPM, WENO, Tadmore central-difference
• MHD 2nd order TVD
• SRHD 2nd order Godunov, Roe solver, R-K stepping
• Source terms
• Nuclear burning variety of reaction networks
• Gravitational field
• Externally imposed
• Self-gravity (multipole, multigrid, single level
  FFT)
• Diffusion
• Thermal
• Conduction

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The FLASH 2 Code Component Model

• 1. Meta-data (Configuration Info)
• Variable/parameter registration
• Variable attributes
• Module requirements
• Role in driver (?)

FLASH Component

• 2. Interface Wrapper
• Exchange with variable database

• 3. Physics Module(s)
• Single patch, single proc functions
• written in any language
• Can be sub-classed

FLASH Application
driver
Collection of Flash Components
Database
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The FLASH 2 Code Application Builder
Configuration Tool (Setup)
Database
Mesh
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The FLASH 2 Code Application Example
Framework
Standard interfaces
Physics Modules (easily interchanged)
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Structure of FLASH Modules
Materials
Hydro
Source_terms
Gravity
init() tstep() hydro3d()
init() tstep() grav3d()
init() tstep() src_terms()
eos3d() eos1d() eos()
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The FLASH 2 Code Directory Structure
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The FLASH 2 Code Additional Features

• External libraries
• MPI for parallel execution
• Paramesh for adaptive discretization
• HDF5 for efficient I/O
• pVTK for remote visualization
• External tools
• Python for configuration
• gmake for code compilation
• http//flash.uchicago.edu
• Available with no major restrictions
• Looking to expand user base
• Support with short response time

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Summary

• FLASH aspires to become a community code
• FLASH is freely available
• Major emphases
• Performance
• Portability
• Testing
• Usability
• Support (secured for at least next 5 years)
• Interest, skill, and organization guarantees
  success
• Future FLASH
• Implicit hydro solvers Front tracking mesh
  component
• Solver and mesh interfaces
• FLASH component model
• FLASH developers guide

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The FLASH Code From Design to Applications
Questions and Discussion
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The FLASH 2 code