Minimizing System Modification in an
Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
Department of Computer and Information Science
Linköpings universitet, Sweden
1 of 10
April 25, 2001
Incremental Design Process
n Start from an already existing system with applications
n Implement new functionality on this system
Mapping and Scheduling
n To reduce design and testing time:
As few as possible modifications of the existing applications
n After the new functionality has been implemented:
It should be easy to add functionality in the future
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
2 of 10
April 25, 2001
Mapping and Scheduling Problem
Future
applications
Do not exist yet
at Version N!
Current
applications
Map and schedule
so that the
future applications
will have a chance
to fit.
Existing
applications
Modify (re-map)
so that the
current applications
will fit.
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
3 of 10
April 25, 2001
Input
n
n
n
n
n
Problem Formulation
A set of existing applications modelled using process graphs.
A current application to be mapped modelled using process graphs.
Each process graph in the application has its own period and deadline.
Each process has a potential set of nodes to be mapped on and a WCET.
The system architecture is given.
Output
n A mapping and scheduling of the current application, so that:
Requirement a: constraints of the current application are satisfied
and minimal modifications are performed to the existing applications.
Requirement b: new future applications can be mapped
on the resulted system.
Notes
n Hard real-time applications
n Static cyclic scheduling of processes and messages
n Time-triggered protocol, TDMA
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
4 of 10
April 25, 2001
Mapping and Scheduling Strategy
n Initial mapping and scheduling
n a) - Satisfying the constraints for the current application
- Minimizing the modification cost
n b) - Prediction of success in adding future applications
- Minimizing the objective function
”An Incremental Approach to the Design of Embedded Systems”, DAC 2001
C = w1P (C1P ) + w1m (C1m ) + w2P max(0, t need − C2P ) + w2m max(0, bneed − C2m )
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
5 of 10
April 25, 2001
Characterizing Existing Applications
150
Γ1
Γ8
70
Γ2
50
Γ3
Γ9
70
Γ4
50
Γ5
Γ6
Γ10
20
Γ7
R({Γ7})=20, R({Γ3})=50, R({Γ3 , Γ7})=70,
R({Γ4, Γ7})=90 (the modification of Γ4 triggers the modification of Γ7),
R({Γ2 , Γ3})=120, R({Γ3 , Γ4 , Γ7})=140, R({Γ1})=150, ....
The total number of possible subsets is 16.
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
6 of 10
April 25, 2001
Mapping and Scheduling, Requirement a)
n Mapping and scheduling of the current application, so that:
Constraints of the current application are satisfied and
minimal modifications are performed to the existing applications.
n Subset selection problem
Select that subset Ω of existing applications which guarantees that the
current application fits and the modification cost R(Ω) is minimized:
R (Ω) =
∑R
Γi ∈Ω
i
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
7 of 10
April 25, 2001
Mapping and Scheduling Strategy
n Initial mapping and scheduling
n Requirement a)
Minimizing the modification cost R(Ω), subset selection:
n Exhaustive Search (ES)
n Ad-Hoc Solution (AH)
n Subset Selection Heuristic (SH)
n Requirement b)
Minimizing the objective function:
”An Incremental Approach to the Design of Embedded Systems”, DAC 2001
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
8 of 10
April 25, 2001
Average Modification Cost R(Ω)
Experimental Results
1200
AH
SH
ES
1000
800
600
400
200
0
320
400
480
560
640
Number of processes
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
9 of 10
April 25, 2001
Conclusions
n Mapping and scheduling of distributed embedded systems
for hard-real time applications.
n Incremental design process
n Already existing system,
n Implement new functionality,
n a) Existing system modified as little as possible,
b) new functionality can be easily added to the system.
n Mapping strategy
n a) Subset selection to minimize modification cost,
n b) Two design criteria, objective function.
Minimizing System Modification in an Incremental Design Approach
Paul Pop, Petru Eles, Traian Pop, Zebo Peng
10 of 10
April 25, 2001