1. Dataflow Machines CMPE 511
İsmail KAHRAMAN
2/12/2004

2. Presentation Outline What is data flow technique?
History of Data Flow Machines
Data Flow Models
Types of Data Flow Systems
Macrodataflow
Conclusion

3. Mechanism on Architectures
Control flow mechanism-von Neumann
Data driven or dataflow mechanism
Demand flow mechanism
Pattern flow mechanism

4. Data Flow Technique
Alternative computer design to stored program systems.
The Difference
Traditional Methods
An instruction executed when the previous instruction in a defined sequence has been executed
In this model,
It is executed when the operands required become available.

5. History
developed in 1960s by Karp and Miller as graphic means of representing computations.
In the early 1970s Denis and others began to develop computer architectures based upon the dataflow computational model.

6. Data Flow Models
It uses a directed graph called a data dependence graph or dataflow graph
arcs
Add
[ ] +
nodes
[ ]
Each node of a data graph can be represented as an activity template
The general flow of the model is top to down

7. Terminology Data, data dependency graph Arcs : flow of the data
Nodes :
represent operations
Token :
represent data and operations
Firing:
when data is available, operation is started, then result is sent to destination.
Handshaking:
Result is consumed

8. Data flow example

9. Switch and Merge
to build
condional and
loop operations

10. Loop graph

11. Static dataflow Recursion is not implemented
Each node can fired only as once instance
Firing rules

12. Firing rules on static Nodes fire Acknowledgement
when all input tokens available
output tokens have been consumed
input token are then removed
output tokens are generated
Acknowledgement
destination sends back signal to source PE when token consumed

13. OPCODE OPERAND DESTINATION
Token format in static
PE receives operation packes of the form
OPCODE OPERAND DESTINATION
PE sends packets of the form
VALUE DESTINATION

14. static dataflow diagram

15. Dynamic data flow Firing rule
A node fires all input tokens with the same tag appear
More than one token is allowed on each arc
Previous output need not be consumed before the node fire again

16. Dynamic data flow architecture

17. Disadvantages of dynamic dataflow
Overhead involved in matching tokens is heavy
Resourse allocation is a complicated process
The long instunction cycle

18. Other types of dataflow mechanism
Pure dataflow
Macro dataflow
Hybrid dataflow

19. Pure Dataflow machines

20. Hybrid data flow

21. MACRO DATA FLOW

22. Conclusion
Dataflow has had a fairly long development time, with a few groups studying the technique without it becoming widespread in commercial use.
Compitability with existing system inhibit the introduction of a radically different computer system requiring a different style of programming and different programming languages.