Brief Announcement: Randomized Rumor Spreading with Fewer Phone Calls

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Brief Announcement Randomized Rumor Spreading
with Fewer Phone Calls

• Kirsten Hildrum
• Sean Ma
• Satish Rao

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The Problem
Soccer game time change! Must tell everyone
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Pushing a rumor
Soccer game time change! Must tell everyone
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A Phone Tree
Soccer game time change! Must tell everyone
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Phone tree problem
Soccer game time change! Must tell everyone
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Our Observation

• Combine the approaches
• Rumor spreading to get around faults
• Tree to finish spreading rumor
• Metrics
• Success rate of players who know the rumor
• Number of phone calls
• Idea Rumor spreading efficient when few know
  rumor, when many know, use tree.
• Long history of rumor spreading algorithms, lots
  of related work, combo idea also used by others
  (eg. Birman et al)

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Reduces failure rate of tree
Success rate vs. failure rate
Percent of nodes notified using Percent of nodes notified using Percent of nodes notified using
failed Tree alone Push alone Pushtree
0 100 88 100
10 2 63 88
20 0 30 60
30 0 10 27
40 0 3 8
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Fewer phone calls than push
Phone calls per node Phone calls per node
Num players Pushtree Rumor spreading
16384 2.2 15.3
65536 2.1 17.4
262,144 2.0 19.6
1,048,576 2.0 22.0
4,194,304 2.0 23.4
10 nodes have failed (note that with pushtree
not all nodes know message)
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Thanks!