Capp 07
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Transcript of Capp 07
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Dataflow Architectures
Topic 7
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Outline
What is data flow technique?
History of Data Flow Machines
Data Flow Models Types of Data Flow Systems
Macrodataflow
Conclusion
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Mechanism on Architectures
Control flow mechanism-von Neumann
Data driven or dataflow mechanism Demand flow mechanism
Pattern flow mechanism
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Data Flow Technique
Alternative computer design to storedprogram systems.
The Difference
Traditional MethodsAn 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.
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History
developed in 1960s by Karp and Miller as
graphic means of representing
computations.
In the early 1970s Dennis and others
began to develop computer architectures
based upon the dataflow computational
model.
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Data Flow Models
It uses a directed graph called a data dependence graph ordataflowgraph
+ nodes
arcs
The general flow of the model is top to down
Each node of a data graph can be represented as an activity template
Add
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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
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Data flow example
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Switch and Merge
to buildcondional and
loop operations
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Loop graph
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Static dataflow
Recursion is not implemented
Each node can fired only as once instance
Firing rules
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Firing rules on static
Nodes fire
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
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Token format in static
OPCODE OPERAND DESTINATION
VALUE DESTINATION
PE receives operation packes of the form
PE sends packets of the form
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static dataflow diagram
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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
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Dynamic data flow architecture
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Disadvantages of dynamic dataflow
Overhead involved in matching tokens is heavy
Resourse allocation is a complicated process
The long instunction cycle
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Other types of dataflow mechanism
Pure dataflow
Macro dataflow
Hybrid dataflow
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Pure Dataflow machines
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MACRO DATA FLOW
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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 programminglanguages.