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Transcript of 11 4 VisIt is a richly featured, turnkey application VisIt is an open source, end user visualization...
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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
2000
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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VisIt: What’s the Big Deal?
Everything works at scale Robust, usable tool Vis to code development to scientific insight
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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 9
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Tutorial schedule
10 minute overview (done) 6 part tutorial on using VisIt
• Introduction• Data analysis / expressions• Scripting• Moviemaking• Comparisons• Alternate data representations
Data model overview Database plugin development example Operator plugin development example Presentation on VisIt architecture / parallel algorithms
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Before we begin…
Tutorial:• Hank Childs ([email protected]), Sean Ahern ([email protected])• Script: http://www.visitusers.org/index.php?Title=Short_Tutorial
• Another tutorial upcoming SC09 User resources:
• Main website: http://www.llnl.gov/visit• Wiki: http://www.visitusers.org• Email: [email protected]
Development resources:• Email: [email protected]• SVN: http://portal.nersc.gov/svn/visit
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AFTER THIS POINT IS THE SLIDES TO CLOSE THE TUTORIAL
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Outline
Parallelism• Contracts• Volume rendering• Streamlines
Data model• AMR• Subset Inclusion Lattices• CSG
Miscellaneous• More on steering• Synthetic Diagnostics
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Contracts are an extension to the standard data flow network design.
Work is performed by a pipeline
A pipeline consists of data objects and components (sources, filters, and sinks)
File Reader(Source)
Slice Filter
ContourFilter
Renderer(Sink)
V0
V1
V2
Exec
Up
dat
e
Execu
te
Data Flow Networks “101”:
Extension:• Contracts are coupled with
the Update phase
• Pipeline execution begins with a “pull”, which starts Update phase
• Data flows from component to component during the Execute phase
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Operating on Optimal Subset of Data
…
Slice Filter
V(I)
…
V(I+1)
Filter(base class)
(inheritance)
Slice FilterHundreds of others
Contract *SliceFilter::ModifyContract (Contract *V(I)){ ... return V(I+1);}
1) Get meta-data2) Determine
domains that intersect slice
3) Restrict list of domains to process in V(I+1)
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Operating on Optimal Subset of Data
…
Slice Filter
V(I)
…
V(I+1) 1) Get meta-data2) Determine
domains that intersect slice
3) Restrict list of domains to process in V(I+1)
D3D2D1D0
D3D2D1D0
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The contract-based system provides high flexibility for this optimization.
…
SphericalSlice Filter
V(I)
…
V(I+1)
A new, plugin filter can use this optimization
without any modification to base data flow network
architecture
…
Slice Filter
V(J)
…
V(J+1)
…
Contour Filter
V(I+1)
V(I)
…
…
Multiple filters can use the same optimizations
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Visualization of massive data requires sophisticated algorithms.
• “Image Space” Partition• Redundant I/O• Each frame requires
new partition
• “World Space” Partition• Camera inside data
set causes huge imbalance.
A hybrid approach that acts as a world space partition, but identifies regions of imbalance and handles those regions using an image space partition.
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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 streamlineexampleNotional 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
P1P2
P3P4
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Hybrid solution:• Master-slave approach that
adapts between parallel inefficiencies and redundant I/O
P0 P0
P1
P1P2
P2 P3P4
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 streamlineexampleNotional streamlineexample
1: Pass
1: Pass1: 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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AMR is handled natively in VisIt
VisIt understands:• Nesting of patches / Boundaries between patches
Strategy:• Each patch is processed separately• After reading data, subsequent passes to:
Identify coarse elements that are refined and mark them as “ghost”
Create ghost layers around outer boundaries (needs work)
UI: • Color by patch, color by level• Remove / show patches, levels • Have appropriate info returned for picks
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CSG Visualization
Adaptively creates a volumetric representation
Supported shapes• Sphere• Cone• Cylinder• Plane• Quadric• Tetrahedron• Pyramid• Prism• Hexahedron
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Users need to reference their data “as they know it”.
Many different decompositions of data:• By simulation processor ID• By material• By part in an assembly• By level/patch for AMR• Plus key subsets, nodes/elements representing:
Boundary conditions Slide surfaces ProbesWe need to allow users to cull away
unneeded subsets of the data.
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Representing data relationships
Relationships between many decompositions are complicated.
Need sophisticated machinery to store this knowledge. Machinery must be customizable to give right “look and
feel”. Idea: incorporate Subset Inclusion Lattices (SIL)
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Subset Inclusion Lattices (SILs)
SIL: directed, acyclic graph
Bipartite: one set of nodes for subsets, the other for categories
Encodes relationships between sets (i.e. subset relations)• Also encodes
“category” of that relation (i.e. material, processor ID, etc)
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VisIt has full built-in support for SILs VisIt supports over fifty file formats.
• Now each can present data subsets to users in an appropriate way.
VisIt can build GUI windows, etc, based on a SIL construction. VisIt creates SILs based on basic information (material
names, # of processors, etc)• Only have to modify a SIL for advanced cases.
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● Simple steering– Scalar inputs to the
simulation– Specified through a GUI
● Dashboard of status
● Built by extending our simulation monitoring
● Simulation code can specify a custom GUI window
– Loaded through a Qt UI file built with Qt Designer
– State is synchronized between VisIt and simulation
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Simulation name
Simulation valuepairs
Simulation statusEngine controls
Commands control
Component name
Text value
Simulation steering
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Quantitative analysis means different things to different people.
1) Techniques that span scientific domains (e.g. integration, volumes, surface areas, fluxes, etc.)
2) Techniques specific to scientific domains (e.g. hohlraum flux at AGEX)
Detectorat AGEX
Detectorprovided by VisIt
(synthetic diagnostic)
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… and we’re done.
Tutorial:• Hank Childs ([email protected]), Sean Ahern ([email protected])• Script: http://www.visitusers.org/index.php?Title=Short_Tutorial
• Another tutorial upcoming SC09 User resources:
• Main website: http://www.llnl.gov/visit• Wiki: http://www.visitusers.org• Email: [email protected]
Development resources:• Email: [email protected]• SVN: http://portal.nersc.gov/svn/visit
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