CMPSCI 677: Homework 3
Due: Friday, April 1 2005, 5pm
Off-campus students: one week from when you view Lecture 13
Web posted: Saturday, March 26 2005
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Describe the benefits of a two-level scheduler implementation of threads
as compared to a user-level and kernel-level threads implementation.
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Consider the iterative and recursive name resolution techniques
and k-level hierarchy of name servers.
- If the one-way cost of communicating from a client to a server is 'C'
and one-way cost of communicating amongst servers is 'S',
determine the cost of name resolution using each of the techniques.
- State the conditions under which each one of them is better than
the other, or if one is always better and reasons for same.
- Give an example to show that Lamport's clock
does not give us the following property:
if C(a) < C(b) then a -> b, where a and b are events,
and C(i) is the clock value assigned to event i.
- Assume vector clocks used for vector ordering, and 'a' and 'b' are
distributed events,
show that if V(a) < V(b) then a->b and vice-versa , i.e.,
if a->b then V(a) < v(b)
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What is the differnce between Weak and Strong mobility?
Give example situations where each one of them can be useful.
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In the Ring algorithm for leader election, more than one elections can be
in operation concurrently in a group. While this does not effect correctness,
nodes send election messages more than once and still elect the same leader.
Suggest a modification to the algorithm to make it more efficient
by reducing number of messages transmitted during concurrent elections.
- What is the advantage of using strict two phase
locking over normal two phase locks? What might be a disadvantage of
strict 2PL?
- Explain why write-ahead logs are prefered to private workspaces in commercial transcational systems?
Prashant Shenoy
Puru Kulkarni