CS 452/652 Winter 2020 - Lecture 26

TC1 Demo Review

Start/Stop Robustness

• being able to quit your program - and restart
  • without reload
  • without reboot
• good for demos, but also helps development
• initialize BSS
• initialize data
• keep constants for initialization
• always/periodically check for exit key

Other Notes

• use headlights to (manually) detect locomotive's travel direction during initialization
• importance of robustness increases between TC1 and final project
• double-check kernel mechanisms: message passing & context switch
• double-check UART servers
• double-check priorities
• double-check main bottleneck: serialization at half-duplex COM1

Routing

Notes

• shortest path routing is often presented as optimal
  but not always the best choice → bottlenecks!
• loop-free: common optimisation criterion required for consistent path computation
  • from the perspective of different nodes
  • especially in distributed setup
• run Dijkstra algorithm only for branch nodes
• use overlay data structure?
• mid-travel reverse - relevant for merge nodes
  model as extra link → augment track data

Path Finding

• online: on-demand routing?
  • compute path using track \ reserved route
  • single-node Dijkstra (overlay) is probably doable online
• offline: determine loop-free alternative path with loop threshold!
  • or take loop to get out of the way