verification of synchronization in specc description with the use of difference decision diagrams
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Verification of Synchronization in SpecC Description with the Use of Difference Decision Diagrams. Thanyapat Sakunkonchak Masahiro Fujita Department of Electronic Engineering University of Tokyo. Content. Introduction Background Verification Flow Verification Results - PowerPoint PPT PresentationTRANSCRIPT
Verification of Synchronization in SpecC Description with the Use of Difference Decision Diagrams
Thanyapat SakunkonchakMasahiro Fujita
Department of Electronic EngineeringUniversity of Tokyo
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Content
Introduction Background Verification Flow Verification Results Conclusion & Future Work
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Introduction
What is SpecC?
Why verification of synchronization?
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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What is SpecC?
Standard system design language for adoption in industry and academia
Handling system design specification->implementation, hardware/software co-design
Build based on ANSI-C
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Why verification of synchronization?
Concurrency (parallel execution) is commonly exist in system design
A kind of scheduling scheme (synchronization) is succinctly needed
In many cases, sophisticated ones will be come up, takes developers lots of time and efforts to verify
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Content
Introduction Background Verification Flow Verification Results Conclusion & Future Work
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Background Timing diagram of statements
execution Concurrency in SpecC with ‘par’
semantic Sequentiality of each behavior in ‘par’ Synchronization semantics
‘notify/wait’ The use of Difference Decision
Diagrams (DDDs)
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Timing diagram of statements execution
Tas<=T1s<T1e<=T2s<T2e<=Tae (sequentiality in a) Tbs<=T3s<T3e<=Tbe (sequentiality in b) Tas=Tbs, Tae=Tbe (concurrency between a and b)
time
a.main()
b.main()
St1 St2
St3
Tas T1s T1e T2s T2e TaeTbs T3s T3e Tbe
time
a.main()
b.main()
St1 St2
St3
Tas T1s T1e T2s T2e TaeTbs T3s T3e Tbe
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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main() { par{ a.main(); b.main(); }} behavior a { main() { x=10; /*st1*/ y=x+10; /*st2*/ }} behavior b { main() { x=20; /*st3*/ }}
time
a.main()
b.main()
St1 St2
St3
Tas T1s T1e T2s T2e Tae
Tbs T3s T3e Tbe
main() { par{ a.main(); b.main(); }} behavior a { main() { x=10; /*st1*/ y=x+10; /*st2*/ notify e; /*New*/}} behavior b { main() { wait e; /*New*/ x=20; /*st3*/ }}
time
a.main()
b.main()
St1 St2
St3
Tas T1s T1e T2s T2e Tae
Tbs T3s T3e Tbe
Synchronization by Notify/wait
Synchronization Example
Ambiguous results of y causing from x = 10; /*st1*/x = 20; /*st3*/
y = 20 (always)
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Difference Decision Diagrams Symbolic representation of non-boolean with
BDD seem to be less efficient DDDs represent different constraints,e.g. x-y≤c,
x and y are integers, c is constant
Represents graph for¬(x−z<1)Λ(x−y≤0)Λ(y−z≤2)
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Content
Introduction Background Verification Flow Verification Results Conclusion & Future Work
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Verification Flow
Goal: check whether the given SpecC codes with ‘par’, ‘notify/wait’ are properly synchronized
Use the idea of ‘Boolean Program’ [Ball and Rajamani]
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Boolean Program
is a subset of the original program obtained by abstracting any
conditionals in ‘if’ statements of the original program with a proportional variable, e.g. if(x > y) -> if(c0)
All statements other than ‘notify/wait’, ‘if’ statements are abstracted away
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SpecC Source Program
Boolean SpecC
C++ with DDD
Parsed & Translated (1)
Parsed & Translated (2)
Verify: Pass?
Constraints from users
Yes
Synchronization is
satisfied
Counter-example No
Check with
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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From SpecC to Boolean SpecC
The event manipulation statements are sustained
The conditional or predicates of all ‘if-else’ statements are automatically replaced by dummy variables, e.g. if(x>0)->if(c0), if(x>4)->if(c1)
Other statements are abstracted away by replacing with SKIP (“…”)
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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From SpecC to Boolean SpecC
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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From Boolean SpecC to C++ with DDD
Header
Branching func.for DDD
Declare timing variables
Setup DDD graphs
Verify
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Content
Introduction Background Verification Flow Verification Results Conclusion & Future Work
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Verification Results
SpecC->Boolean SpecC->C++ with DDDthe process are automatic
Using C++ compiler and DDD package to verify the synchronization of SpecC
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Verification Results
SATISFIED UNSATISFIED DON’T KNOW
In the case of UNSATISFIED, the counter-example is given to track the unsatisfied source
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Verification Result Let see an example
There is no chance for the event e to be satisfied if the conditions (x<y) and (x>=y) must be true at the same time
if(x<y)
notify e;
else
statement;
if(x>=y)
wait e;
else
statement;
par
Thread a Thread b
if(c1)
notify e;
else
...;
if(c2)
wait e;
else
...;
par
Thread a Thread b
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Content
Introduction Background Verification Flow Verification Results Conclusion & Future Work
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Conclusion The verification of synchronization in
SpecC description was proposed The idea of Boolean program is used
to abstract away some details Collaborate with DDD, we can verify
for synchronization in original SpecC Counter-example and verification of it
is considered to be accomplished (on-going work)
July 23, 2002 T. SAKUNKONCHAK and M. FUJITA University of Tokyo
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Future Work
for users to interactively input constraints
provide counter-example when the synchronization is not satisfied
to be able to automatically generate ‘predicates’
refining predicates or add constraints on predicates