lect10b.pdf

Bounded Model Checking
void f(...) {
...
while(cond) {
Body;
}
Rest;
}
Comp 3153 Ansgar Fehnker
Bounded Model Checking
void f(...) {
...
if(cond) {
Body;
if(cond) {
Body;
while(cond) {
Body;
}
}
}
Rest;
}
Comp 3153 Ansgar Fehnker
Bounded Model Checking
void f(...) {
...
if(cond) {
Body;
if(cond) {
Body;
if(cond) {
Body;
if(cond) {
assert(FALSE);
}
}
}
}
Rest;
}
Comp 3153 Ansgar Fehnker
Rather than checking infinite
loops, check finite unwinding
� Unwind while() loops
Rather than checking infinite
loops, check finite unwinding
� Unwind while() loops
Rather than checking infinite
loops, check finite unwinding
� Unwind while() loops
� Until the bound k is
reached
� Add assertion after last
iteration.
Check whether error is
real or due to
insufficient bound k.
Bounded Model Checking
void f(...) {
...
if(cond) {
Body;
while(cond) {
Body;
}
}
Rest;
}
void f(...) {
...
if(cond) {
Body;
if(cond) {
Body;
if(cond) {
Body;
while(cond) {
Body;
}
}
}
}
Rest;
}
Comp 3153 Ansgar Fehnker
Bounded Model Checking
Comp 3153 Ansgar Fehnker
Rather than checking infinite
loops, check finite unwinding
� Unwind while() loops
Rather than checking infinite
loops, check finite unwinding
� Unwind while() loops
� Until the bound k is
reached
Bounded Model Checking
Basic Idea
� Show absence of counterexamples of length k
� Translate model checking problem to SAT problem
� Use SAT solver to show absence of counterexamples.
� Complete for sufficiently large k
Comp 3153 Ansgar Fehnker
Based on
presentations Daniel
Kroening and Ofer
Shtrichman
2