visit: a visualization tool for large turbulence simulations
DESCRIPTION
VisIt: a visualization tool for large turbulence simulations. 27B element Rayleigh-Taylor Instability (MIRANDA, BG/L). - PowerPoint PPT PresentationTRANSCRIPT
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27B elementRayleigh-Taylor Instability(MIRANDA, BG/L)
VisIt: a visualization tool for large turbulence simulations
Large data requires special techniques. This image was made by using a distributed
memory parallel program that partitioned the data over the processors, performing I/O,
processing, and rendering in parallel.
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VisIt calculated connected components on a 4K^3 turbulence data in parallel using TACC's Longhorn machine. 2 million components were initially identified and then the map expression was used to select only the components that had total volume greater than 15. Data courtesy of P.K. Yeung & and Diego Donzis
Visualizing and Analyzing Large-Scale Turbulent Flow
Detect, track, classify, and visualize features in large-scale turbulent flow.
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Flow analysis for 217 pin simulation / 1 billion grid points
217 pin reactorcooling simulation.Run on ¼ of Argonne BG/P.
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Flow analysis for 217 pin simulation / 1 billion grid points
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Tracing particles through the channels
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Tracing particles through the channels
Place 1000 particles in one channel
Observe which channels the particles come out
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This analysis depended on improvements in parallel particle advection
Two extremes:• Partition data over processors
and pass particles amongst processors Parallel inefficiency!
• Partition seed points over processors and process necessary data for advection Redundant I/O!
Notional streamlineexample
Notional streamlineexample
P0 P0 P0 P0 P0
P1 P1 P1 P1 P1
P2 P2 P2 P2 P2
P3 P3 P3 P3 P3
P4 P4 P4 P4 P4
P0
P1
P2
P3
P4
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Hybrid solution:• Master-slave approach that
adapts between parallel inefficiencies and redundant I/O
P0P0
P1
P1
P2
P2P3
P4
Iteration Action
0 P0 reads B0,P3 reads B1
1 P1 passes points to P0,P4 passes points to P3,P2 reads B0
0: Read
0: Read
Notional streamlineexample
Notional streamlineexample
1: Pass
1: Pass
1: Read
- Decision of when to pass or read is simplified here and based on load of
processors owning data. - Heuristic weights against I/O, but allows
for redundant I/O- All coordination done by slave masters.
This analysis depended on improvements in parallel particle advection
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VisIt is a richly featured, turnkey application
• VisIt is an open source, end user visualization and analysis tool for simulated and experimental data
– Used by: physicists, engineers, code developers, vis experts
– >100K downloads on web
• R&D 100 award in 2005• Used “heavily to exclusively” on 8
of world’s top 12 supercomputers
217 pin reactor coolingsimulation. Run on ¼ of Argonne BG/P.
1 billion grid points
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Terribly Named!! Intended for more than just visualization!
Data Exploration
VisualDebugging Quantitative Analysis
Presentations
=?
Comparative Analysis
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VisIt has a rich feature set that can impact many science areas.
Meshes: rectilinear, curvilinear, unstructured, point, AMR Data: scalar, vector, tensor, material, species Dimension: 1D, 2D, 3D, time varying Rendering (~15): pseudocolor, volume rendering,
hedgehogs, glyphs, mesh lines, etc… Data manipulation (~40): slicing, contouring, clipping,
thresholding, restrict to box, reflect, project, revolve, … File formats (~85) Derived quantities: >100 interoperable building blocks
+,-,*,/, gradient, mesh quality, if-then-else, and, or, not Many general features: position lights, make movie, etc Queries (~50): ways to pull out quantitative information,
debugging, comparative analysis
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VisIt employs a parallelized client-server architecture.
Client-server observations:• Good for remote
visualization• Leverages available
resources• Scales well• No need to move data
Additional design considerations:• Plugins• Multiple UIs: GUI (Qt), CLI
(Python), more…
remote machine
Parallel vis resources
Userdata
localhost – Linux, Windows, Mac
Graphics Hardware
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The VisIt team focuses on making a robust, usable product for end users.
Manuals• 300 page user manual• 200 page command line interface manual• “Getting your data into VisIt” manual
Wiki for users (and developers) Revision control, nightly regression testing, etc Executables for all major platforms Day long class, complete with exercises
Slides from the VisIt class
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VisIt is a vibrant project with many participants.
Over 50 person-years of effort Over one million lines of code Partnership between: Department of Energy’s Office of Nuclear
Energy, Office of Science, and National Nuclear Security Agency, and among others
2004-6
User communitygrows, includingAWE & ASC Alliance schools
Fall ‘06
VACET is funded
Spring ‘08
AWE enters repo
2003
LLNL user communitytransitioned to VisIt
2005
2005 R&D100
2007
SciDAC Outreach Center enablesPublic SW repo
2007
Saudi Aramcofunds LLNL to support VisIt
Spring ‘07
GNEP funds LLNL to support GNEP codes at Argonne
Summer‘07
Developers from LLNL, LBL, & ORNLStart dev in repo
‘07-’08
UC Davis & UUtah research done in VisIt repo
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Project started
‘07-’08
Partnership withCEA is developed
2008
Institutional supportleverages effort from many labs
Spring ‘09
More developersEntering repo allthe time
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● Weak scaling study: ~62.5M cells/core
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#coresProblem Size
ModelMachine
8K0.5TIBM P5Purple
16K1TSunRanger
16K1TX86_64Juno
32K2TCray XT5JaguarPF
64K4TBG/PDawn
16K, 32K1T, 2TCray XT4Franklin
VisIt was recently demonstrated to show good performance at unprecedented scales.
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Three Ways To Get Data Into VisIt
(1) Write to a known output format (2) Write a plugin file format reader (3) Integrate VisIt “in situ”
• “lib-VisIt” is linked into simulation code (Note: Memory footprint issues with
implementation!)• Use model:
simulation code advances at some time interval (e.g. end of cycle), hands
control to lib-VisIt. lib-VisIt performs vis & analysis tasks, then hands
control back to simulation code repeat 16
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VisIt: What’s the Big Deal?
What’s the big deal?• Everything works at scale• Robust, usable tool• Vis to code development to scientific insight
Learn more:• Google: “visit visualization”• http://www.llnl.gov/visit / http://www.visitusers.org• [email protected]
Live & online tutorials• Publicly available SVN• Hank Childs,