MACCE and RealTime Schedulers

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MACCE andReal-Time Schedulers

• Steve Roberts
• EEL 6897

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Who Am I?

• Masters in Modeling and Simulation
• Employed by Veraxx Engineering Corp.
• Undergraduate in Computer Engineering from UCF
• Worked in the simulation industry 4 years

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Agenda

• Discuss some different simulation issues
• Define a scheduler or real-time executive
• What is MACCE?
• A MACCE configuration file
• Conclusion
• Questions

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Some Simulation Issues

• Real-Time cards
• Interrupts
• Multiple Language Support
• Callbacks
• Shared Memory
• Multi-Threading

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Real Time Cards

• Sync cards
• Provide interrupts
• Interrupts can occur at different frequencies
• More accurate than software interrupts

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Multiple Language Support

• Fortran
• ADA/ADA 95
• C
• C
• Many simulators that are upgraded are comprised
  of legacy code and code from other simulators are
  pulled in to these legacy systems

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Callbacks

• A pointer to a function
• Usually the function is in a high level language
• The function pointer is passed to a low level
  language
• May also exist within the same application (high
  level/high level)

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Shared Memory

• Block of memory used by different processes
• Hardware shared memory
• Multiple CPUs
• Software shared memory
• Single CPU

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SCRAMNet

• Shared Common Random Access Memory Network
• Ring architecture
• Fiber Optic Network
• Large Throughput
• gt200MB/s
• Automatically updates other CPUs

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Multi-Threading

• Multiple processes running at the same time
• Multiple CPU
• Multiple threads/callbacks on a single CPU

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What Is A Scheduler?

• A scheduler is a piece of software that is an
  integration point for a simulation. It is where
  all the variables are instantiated, where the
  functions are called, where proper timing and
  order of execution happens, and where a
  simulation is initialized, executed and
  terminated.

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Why Have a Scheduler?

• Simplifies and automates integration
• Wraps many low level details
• Automatically handles many low level details
• Provides a common simulation environment
• Provides simple debuggin and analysis tools

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What is MACCE?

• Marine Aviation Common Computing Environment
• Manages and controls a Vehicle Simulation
  Environment in real-time and standalone modes
• Linux based C architecture
• Takes advantage of multiple CPUs

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MACCE System Diagram
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MACCE Architecture

• Server
• Client
• Daemon
• Graphical User Interface (GUI)

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MACCE Server

• This is the main process
• Reads the configuration file
• Creates the control table in shared memory
• Starts all the clients
• Monitors the command line
• Does not perform real-time tasks

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MACCE Server Cont.

• Configures MACCE Memory Manager (M3) global areas
• Can be started in debug mode
• Debugger such as GDB can be used to step through
  any of the callbacks in the simulation

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MACCE Client

• MACCEC
• This is a process
• Connects to the control table
• All callbacks are initiated by the client
• One MACCEC per CPU is recommended
• Has top level exception handling
• Can manage multiple threads.

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MACCE Daemon

• Monitors a port for MACCE commands from MACCE
  Clients
• Forwards those commands to the MACCE server
• Runs on a Linux machine
• One instance runs

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MACCE GUI

• More of a text-based UI
• Provides interface for printing and watching
  variables
• Provides timing statistics
• Displays log messages
• Used to terminate a MACCE Server instance

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MACCE Memory Manager (M3)

• Lays out shared data areas
• Reads in a memory config file
• Generates Fortran scan file
• Generates C, C header file
• Generates Ada records

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MACCE API
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MACCE Configuration File

• Variables
• SETENV
• GLOBAL
• Clocks
• Modes
• Callbacks
• Tables
• Threads
• Processes

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Sample MACCE Configuration

• //////////
• // clocks
• //////////
• CLOCKS
• external 0
• internal 60
• standalone 10
• /////////
• // modes
• /////////
• MODE
• name STARTUP_MODE
• description Startup mode
• type ONESHOT
• next FREEFLIGHT_MODE

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Cont

• /////////////
• // callbacks
• /////////////
• CALLBACK
• name EOM_STARTUP_CALLBACK
• description Equations of motion startup
  callback
• symbol eom_startup
• language CPP
• CALLBACK
• name EOM_SHUTDOWN_CALLBACK
• description Equations of motion shutdown
  callback
• symbol eom_shutdown
• language CPP
• CALLBACK
• name EOM_SIMULATE_CALLBACK
• description Equations of motion simulate
  callback

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Cont

• ///////////
• // threads
• ///////////
• THREAD
• name STARTUP_THREAD
• description Startup Thread
• mode STARTUP_MODE
• frequency 1
• phase 0
• callback EOM_STARTUP_CALLBACK
• callback UHF_RADIO_STARTUP_CALLBACK
• callback TACAN_STARTUP_CALLBACK
• THREAD
• name SHUTDOWN_THREAD
• description Shutdown Thread
• mode SHUTDOWN_MODE
• frequency 1

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Cont

• /////////////
• // processes
• /////////////
• PROCESS
• name TUTORIAL1_PROCESS
• description tutorial1 process
• filter 1
• cpu 1
• thread STARTUP_THREAD
• thread SHUTDOWN_THREAD
• thread FREEFLIGHT_60HZ_THREAD
• thread FREEFLIGHT_30HZ_PHASE0_THREAD
• thread FREEFLIGHT_30HZ_PHASE1_THREAD

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Conclusion

• MACCE is a great tool that allows software
  engineers the ability to pull together many
  different pieces of simulators and combine them
  to build a new simulator
• MACCE also provides software engineers with a
  debugging environment
• MACCE can save time and headaches

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Questions?