pysph: a python framework for sph
TRANSCRIPT
PySPH: A Python framework forSPH
Prabhu RamachandranChandrashekhar P. Kaushik
Department of Aerospace Engineering andDepartment of Computer Science and Engineering
IIT Bombay
SciPy 2010Austin, TX, June 30 – July 1, 2010
Outline
Introduction
PySPH
Architecture
Outline
Introduction
PySPH
Architecture
SPH examples
SPH examples
3D
Parallel?
Smoothed Particle HydrodynamicsI Particle based, LagrangianI Gingold and Monaghan (1977),
Lucy (1977)
I PDEsI Complex problemsI Moving geometriesI Free surface problemsI . . .
Smoothed Particle HydrodynamicsI Particle based, LagrangianI Gingold and Monaghan (1977),
Lucy (1977)
I PDEsI Complex problemsI Moving geometriesI Free surface problemsI . . .
SPH basics
I The SPH approximation
f (r) =∫
f (r ′)W (r − r ′, h)dr ′
I W (r − r ′, h): kernel, compact supportI h: size of the kernel
SPH basics
SPH basics
neighbors
kh
Nearest
SPH basics . . .
I Derivatives: transferred to the kernelI Lagrangian
I PDE → ODE
Scale-up for larger problemsrequires parallelization
Motivation
Reproducible and open research
Outline
Introduction
PySPH
Architecture
Requirements and installation
I Python, setuptoolsI numpy, Cython-0.12,
mpi4py-1.2I Mayavi-3.x (optional)I Standard Python package
install
High-level solver outline
Serial Dam break
so l ve r = FSFSolver ( t ime_step =0.0001 ,t o t a l _ s i m u l a t i o n _ t i m e =10. ,ke rne l=CubicSpline2D ( ) )
# create the two e n t i t i e s .dam_wall = So l i d (name= ’ dam_wall ’ )dam_f lu id = F lu i d (name= ’ dam_f lu id ’ )
# The p a r t i c l e s f o r the wa l l .rg = RectangleGenerator ( . . . )dam_wall . add_par t i c l es ( rg . g e t _ p a r t i c l e s ( ) )so l ve r . add_en t i t y ( dam_wall )
Serial Dam break . . .
# P a r t i c l e s f o r the l e f t column of f l u i d .rg = RectangleGenerator ( . . . )dam_f lu id . add_par t i c l es ( rg . g e t _ p a r t i c l e s ( ) )so l ve r . add_en t i t y ( dam_f lu id )
# s t a r t the so l ve r .so l ve r . so lve ( )
Parallel Dam break
so l ve r = Para l le lFSFSolver (t ime_step =0.0001 ,t o t a l _ s i m u l a t i o n _ t i m e =10. ,ke rne l=CubicSpline2D ( ) )
# Load p a r t i c l e s i n proc wi th rank 0 .
Outline
Introduction
PySPH
Architecture
Software architecture
I Particle kernelI SPH kernelI Solver frameworkI Serial and Parallel solvers
Software architecture
Solver Framework
NNPS
SPH
Cell Manager
Particle Arrays
Solvers
(Python & Cython)(Cython)
(Cython)
(Cython)
(Cython)
C−Arrays (Cython)
Particle kernel
I C-arrays: numpy-like but faster andresizable
I ParticleArray: arrays of propertiesI NNPS (Nearest Neighbor Particle
Search)I Cell, CellManagerI Caching
SPH kernel
I SPH particle interaction: interactionbetween 2 SPH particles
I SPH summation: interaction of allparticles
Solver framework
I Entities (made of particles)I Solver components (do various things)I Component manager (checks
property requirements)I IntegratorI Basic Solver
Parallel solver
I Parallel cell managerI Parallel solver components
Parallel solver
CellManager
Processor 1 Processor 2
Particles
Solver components
Particles
Solver components
Parallel case
ParallelCellManager ParallelCellManager
Serial case
Particles
Solver components
Challenges
I Particles move all overI Fixed partitioning will not workI Scale upI Automatic load balancing?
Terminology: Cell
Cells
Particles
Terminology: Region
Region 2
P1 P2
Region 1
P2
O
(−1,−1,0)
(1,1,0)
(1,−1,0)
(2,0,0)
P1
P3
P4
Terminology: Domain decomposition
Approach
I Domain decomposition: CellsI Cells: dynamically created/destroyedI Processors manage RegionsI Cells moved to balance load
Load Balancing
Donate CellsI Boundary cellsI Cells with least number of local
neighbors
Load balancing
Efficiency
Efficiency
Current capabilities
I Fully automatic, load balanced,parallel framework
I Relatively easy to scriptI Good performanceI Relatively easy to extend
I Free surface flows
Immediate improvements
I Solver framework redesignI More documentationI Reduce dependency on TVTK for
easier installationI Improved testing on various platformsI Gas dynamics (coming soon)I Solid mechanics (next year)
Thank you!