Distributed Simulation and MultiStep Capabilities in VTB

1
Distributed Simulation and Multi-Step
Capabilities in VTB
2005 VTB Users and Developers Conference September
20, 2005

• Rod Leonard
• Graduate Student
• Dept of Electrical Engineering
• University of South Carolina

2
Overview

• New Virtual Test Bed architecture
• Non-uniform time stepping
• Distributed Simulation
• Shared memory
• Beowulf clusters
• Other features

3
VTB Architecture
Schematic Editor
Schematic Editor
Math Engine
thr1
thr2
thr3
4
VTB as Multi-Solver Environments
Solver 2
Solver 1
Schm 1
Schm 2

• Focus switching
• Context switching
• Hierarchy of models
• System matrix order change

5
Database

• Database interaction occurs on a plugin-based
  system
• Any SQL relational database can be supported if a
  compatible plugin is developed
• First supported database will be PostgreSQL

6
Database, cont.

• Contents
• All registered computers and their addresses
• Schematic information
• Full state information for every time step of a
  simulation
• All viewables from a simulation

7
Simulation Backend

• Advantages
• Parallelism
• Increased Robustness
• Disadvantages
• Network delay
• Database Overhead

8
Client Connection

• Advantages
• Visualization modes available to any solver
• Multiple clients may connect to the same
  simulation

9
Non-Uniform Time Stepping

• Motivation
• In a complete system simulation, some parts of
  the system may have a much faster response time
  than others, for example, an electrical control
  and a mechanical plant
• Instead of stepping the entire system at the
  lowest time step, we may separate the system into
  separate subsystems according to stepping
  requirements

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Example System
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Separated System
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Information Exchange

• Zero order hold
• Always used when extracting information from a
  simulation running at a lower time step
• Average
• Available for use when extracting information
  from a simulation running at a higher time step

13
Future

• Predictive algorithms
• Methods to predict values for interim time-steps
  from a simulation running at a higher time step
• Nature coupling
• Methods to perform non-uniform stepping with
  nature coupling

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Distributed Simulation

• Shared Memory
• Multi-threaded operations concerning matrix
  operations occur in each solver process
• When multiple solver processes are assigned to
  the same computer
• Beowulf Cluster
• When different processes are assigned to separate
  computers

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Shared Memory

• Used automatically within a single solver
• Solver divides system calculation in multiple
  threads
• SMP systems are also taken advantage of
  automatically when system when running in
  non-uniform time step mode where multiple parts
  are being run on the same computer

16
Beowulf Cluster

• Computations may occur in parallel in different
  computers by assigning different parts of the
  simulation to different computers
• User determines how to divide simulation
• Advantages should be seen when running in
  non-uniform time-step modes

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Mixed Architectures

• Supercomputer
• Server farms
• Workstations

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Future

• Solver will automatically use computer clusters
  for internal matrix operations, similar to the
  method used with shared memory
• Availability to divide a simulation in different
  parts without breaking the schematic into
  different parts

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Other Features

• Multiple-steps rollback features
• Control of simulation backend via web browser
• Separation of systems within the same schematic
• Added network communication features to allow for
  better cooperation between engineers at separate
  physical locations

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Network Cooperation

• One engineer creates an overall system schematic
• Another creates a detailed section of a subsystem
• Each can perform their simulation over the
  network making pseudo real-time changes and
  observing only their area of interest.

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Network Cooperation

• Saved viewable preferences
• Real-time communication
• Tracking of changes

22
Multiple-Step Rollback

• Database has full simulation information
• Ability to roll back to any previous point in the
  simulation

23
Web Interface

• From any computer / architecture
• Schedule commands
• Access saved content

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Easier System Separation
25
Current Status

• Signal coupled non-uniform time step systems
• Done
• Shared memory parallelism
• Done for uncoupled systems
• Cluster parallelism
• 90 done for non-uniform time-step systems
• Multiple step rollback
• 35 done
• Other features to be implemented