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Key considerations for multithreaded architectures in LabVIEW
- 1. Piotr Demski piotr.demski@sparkflow.pl Key Considerations for Multithreaded Architectures
- 2. What We Do? Custom Software Development Outsourcing Consulting Hardware Integration Sparkflow Sp z o.o. Kolejowa 57 40-602 Katowice Poland
- 3. We’re experts in NI Platform • PXI • cDAQ • cRIO, sbRIO • USRP • Machine Vision Systems Real-Time FPGA
- 4. Agenda The case Is single loop enough? Applications of multithreaded architecture Architecture design
- 5. Scope Applications that use multiple loops running in parallel
- 6. The Case • Create the application for the test stand. • 4 independent test slots. • Some test hardware is shared between slots. • Operator mounts the UUT in the slot and starts test. Operator then mounts another UUT in another slot. • Operator needs some control over the slot when mounting UUT. • Application needs to communicate with PLC and other equipment.
- 7. Is single loop enough for this application?
- 8. Simple State Machine • A single loop that combine user interface control and application logic. *File->Create Project->Simple State Machine
- 9. Simple State Machine • How do we handle multiple slots? • How do we handle user interaction during test? • How do we handle PLC and other equipment communication? *File->Create Project->Simple State Machine
- 10. (Some) Applications of multithreaded architectures Improving User Interface responsiveness Parallel processing
- 12. Improving User Interface responsiveness • 0.1 second is about the limit for having the user feel that the system is reacting instantaneously • 1.0 second is about the limit for the user's flow of thought to stay uninterrupted • 10 seconds is about the limit for keeping the user's attention *Jakob Nielsen, Usability Engineering (1993)
- 13. Queued Message Handler • Respond to user actions instantaneously in Event Handling Loop • Offload any processing to Message Handling Loop *File->Create Project->Queued Message Handler
- 14. Considerations • Make User Interface independent from the application logic.
- 15. Considerations • Make User Interface independent from the application logic. • Focus on proper messages design.
- 16. Considerations • Make User Interface independent from the application logic. • Focus on proper messages design. • Start project using existing architecture (QMH, Delacor QMH, your own code).
- 17. Considerations • Make User Interface independent from the application logic. • Focus on proper messages design. • Start project using existing architecture (QMH, Delacor QMH, your own code). • Consider splitting UI into multiple VIs.
- 19. How to make 4 independent slots? • Design a single Slot. • Use 4 instances of this Slot in application. • Design a single Test Stand that controls 4 Slots. • Use 1 instance of Test Stand in application.
- 20. Single Test Stand • Slots are processed sequentially. They should not do too much processing. • Any message to the Slot must be sent to the Test Stand with proper Slot ID.
- 21. Multiple Slot instances • Every slot is independent from another. They can do heavy processing internally without blocking each other. • Any message must be send to proper slot using this slot specific communication channel. • Slot VI and all subVIs must be reentrant (harder debugging).
- 22. Considerations • Select the right architecture for your application.
- 23. Considerations • Select the right architecture for your application. • Consider alternatives.
- 24. Considerations • Select the right architecture for your application. • Consider alternatives. • Identify blocking and time-consuming operations, move them to other threads.