Parallel LTL Model Checking CS 586. The Capacity Problem Capacity = memory states*stateSize Increase...
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Transcript of Parallel LTL Model Checking CS 586. The Capacity Problem Capacity = memory states*stateSize Increase...
Parallel LTL Model Checking
CS 586
The Capacity Problem
Capacity = memory states*stateSize
Increase capacity by- Increasing memory- Decreasing states- Decreasing state size
Double DFS in Parallel
Memory available in one machine
Memory needed to store visited states
DDFS Search order
A B
C
If the dfs2 from A visits C first, then the dfs2 from B will not visit C and will not detect a cycle.Solutions?
Solution Ideas
Use a different algorithm.
Schedule the dfs2 searches
Use different bits to mark dfs2 visits
______ ?
One Idea
Forget about proving correctness.
Each search process is random.
Coordinate efforts to find cycles.
Coordination scheme should be..Decentralized
Fault-tolerant
Better than no coordination at all
Forager Allocation Problem
Given: several foraging sites with varying qualitythe current needs of the hivea pool of foragers
Allocate the foragers to: maximize the collection of needed resources
Without central control.
Scouts locate patches
Scouts multicast their findings
Scout performs a waggle dance whichis observed by unemployed foragers.Duration and intensity of the dance describe the quality of the patch.
Workers visit patches.
A worker will observe a dance and leave for a patch.Returns, unloads and dances.May visit patch again.
Adaptation
Apis Mellifera
Bee foragerSearch flight patternFlower patchPollenWaggle dance
BEE(bee-based error explorer)
Search agent
Random walk
Accept state
Property Violation
Multicast
Decentralized Cooperative Search
A B
C
Launch n random searches.When one finds an accept state, advertize its location.Listen to and possibly ignore advertizements.
BEE Search
controller BEE BEE BEE BEEdistributeproblem
BEE Search
controller
multicast anaccept state
BEE Search
controller
moremulticasts
report an error
BEE Search
controller
searchcontinues…
BEE Search
controller
search terminated
Experimental Environment
Classroom laboratory workstations
Lowest priority level
8 MB of RAM per machine
Compare with isolated parallel random walks to measure advantage of coordination.
Speedup-SS7
0
10
20
30
40
50
60
70
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64
BEE
ISO
Linear
Speedup-11peterson
0
10
20
30
40
50
60
70
2 64
BEE
ISO
Linear
0
0.5
1
1.5
2
2.5
3
3.5
0 16 32 48 64 80 96 112 128
Workstations
Advantage of cooperation
ss7
11p
ss8
Too Much CommunicationSS 7 11 Peterson
0
1
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3
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9
10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
msgs recvd
acc states found
dfs2 replaced
0
10
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30
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50
60
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45
msgs recvd
acc states found
DFS2's replaced
0
1
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3
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7
8
9
10
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47
msgs recvd
acc states found
dfs2 replaced
ACCEPT STATEFORAGING
time to receivecycle advertisement
recruit to cycle foraging
abandon acceptstate foraging
WATER COLLECTING
water in hive
recruiting to water collecting(waggle dance)
abandoning of water
collecting
water seekingby receiver bees
time to findan unloader
evaporativecooling
Negative Feedback
Negative Feedback
