Suppose an event x in a distributed system has a scalar timestamp of 29 and d = 1. What can be
inferred conclusively?
Select one:
28 events in the entire distributed system causally precede x
There are total 10 message send events in the entire distributed system
The local clock component of x is 14
There are 14 processes in the distributed system
Suppose a distributed system contains 5 processes - P1, P2, P3, P4 and P5. An event a occurring at
P4 has a vector timestamp [7 4 3 5 2]. Assume d = 1.Calculate the total number of events that
causally precede a in the entire distributed system.
Select one:
20
5
7
21
Suppose a distributed system contains 10 processes. The Chandy-Lamport algorithm is used for
recording the global snapshot for this system. How many times will each process execute the marker
sending rule?
Select one:
none of the options are correct
9
10
1
A distributed system uses Fowler–Zwaenepoel’s Direct-Dependency Technique for implementing
vector clocks. There are 6 processes in this distributed system - P1, P2, P3, P4, P5 and P6. P3
sends a message to P6 and the vector timestamp of this message send event is [5 4 3 6 2 5]. What
will be the timestamp of the message sent by P3 to P6? Assume d = 1.
Select one:
3
4
6
5
Suppose an event e has a vector timestamp of [4 3 6 7 5 7 4] in a distributed system consisting of 7
processes, P1, P2, P3, P4, P5, P6 and P7. e has occurred on process P4. Assume d = 1. What is
the number of events executed by P3 that causally precede e ?
Select one:
4
6
7
5
Suppose there is a distributed system consisting of 6 processes - P1, P2, P3, P4, P5 and P6.
Consider the two processes P2 and P4. P2 sends 2 messages to P4. These 2 are successive
message send events. There are other events occurring in the distributed system. Assume d = 1.
For the 1st message send event from P2 to P4, the vector timestamp of the send event is [4 3 2 0 2
3]. For the 2nd message send event from P2 to P4, the vector timestamp of the send event is [5 4 3
0 4 3]. As per Singhal-Kshemkalyani's Differential Technique, the vector timestamp of the message
sent during the 2nd message send event from P2 to P4 is
Select one:
{(2, 4), (3, 3), (6, 3)}
{(1, 5), (2, 4), (3, 3), (5, 4), (6, 3)}
{(1, 5), (2, 4), (3, 3), (5, 4)}
{(1, 5), (2, 4), (3, 3)}
The Lai-Yang algorithm for global snapshot recording computes the states of the channels using
which of the following? Answer the question by considering only the type of the messages.
Select one:
both red and white messages
only the marker messages
only the white messages
only the red messages
Which of the following is false?
Select one:
The Chandy-Lamport algorithm for global snapshot recording is applicable for communication
channels following causal ordering model
The Chandy-Lamport algorithm for global snapshot recording is applicable for FIFO communication
channels
The Chandy-Lamport algorithm for global snapshot recording is not applicable for communication
channels following causal ordering model
The Chandy-Lamport algorithm for global snapshot recording is not applicable for non-FIFO
communication channels
What is the termination criterion for the Chandy-Lamport algorithm for global snapshot recording?
Select one:
each process has received a marker along each of its incoming channels
each process has received a marker along each of its incoming and outgoing channels
each process has received a marker along a subset of its incoming channels
each process has received a marker along each of its outgoing channels
In a consistent global state
Select one:
if a message is recorded as sent in the local state of the sender process, then the message has to be
recorded as received in the local state of the receiving process
if a message is recorded as sent in the local state of the sender process, then the message is either
recorded as received in the local state of the receiving process or included in the state of the
corresponding communication channel
if a message is recorded as sent in the local state of the sender process, then the message has to be
included in the state of the corresponding communication channel
if a message is recorded as sent in the local state of the sender process, then the message is never
recorded as received in the local state of the receiving process
Which of the following is not true?
Select one:
A consistent cut takes into account scenarios where the effect is seen without its cause
A message never crosses a consistent cut from the FUTURE to the PAST
A message crossing a cut from the PAST to the FUTURE is captured in the corresponding channel
state
A cut is consistent if no event in the FUTURE of the cut happened before an event in the PAST of the
cut
Consider an 8-dimensional hypercube. Suppose the hamming distance between the labels of 2
nodes n1 and n2 of this hypercube is 6. What is the length of the shortest path between n1 and n2?
Select one:
5
8
6
7
Consider 2 vector timestamps v1 = [4 3 7 2] and v2 = [3 2 5 0]. Which of the following is true?
Select one:
v1 = v2
v2 < v1
v1 < v2
v1 || v2
Which of the following is true for Lai-Yang algorithm for global snapshot recording?
Select one:
each process records the states of all of its incoming and outgoing channels
a red process is a process who has already recorded its local state
a white process sends red messages
a red process sends white processes
Which of the following is false?
Select one:
The concurrency relation for events is transitive
The concurrency relation for events is non-transitive
The happens before relation for events is transitive
Causal ordering model is based on happens before relation for events
Which of the following is false?
Select one:
latency to access different memory locations from different processors varies in the NUMA model
array processors are loosely coupled
multicomputer parallel systems are very tightly coupled
a 6 x 6 2-D wraparound mesh contains 36 processors
If an Omega network uses 8 bits for addressing, calculate the number of processors that is
associated with this network.
Select one:
128
64
512
256
A distributed system uses Fowler–Zwaenepoel’s Direct-Dependency Technique for implementing
vector clocks. There are 5 processes in this system - P1, P2, P3, P4 and P5. An event e occurs on
P2. e is a message send event and has a vector timestamp of [6 8 5 4 5]. Calculate the number of
events occurring on P2 that causally precede e. Assume d = 1.
Select one:
5
7
6
sufficient information is not given
Consider the 8-input and 8-output 3-stage Omega network that we have studied in the contact
session. If data is to be routed to a memory bank having the address 101 from the processor having
the address 011, what is the sequence of routing the data on the different wires through the
successive stages 0, 1 and 2? Here, we consider that stage number starts from 0.
Select one:
lower wire in stage 0, lower wire in stage 1, lower wire in stage 2
lower wire in stage 0, upper wire in stage 1, upper wire in stage 2
upper wire in stage 0, upper wire in stage 1, lower wire in stage 2
lower wire in stage 0, upper wire in stage 1, lower wire in stage 2
CORBA stands for
Select one:
Common Object Response Broker Architecture
Common Object Request Broker Architecture
Common Object Request Binding Architecture
Central Object Request Broker Architecture
Which of the following is not true for a distributed system?
Select one:
Absence of shared memory
Middleware takes care of heterogeneity among various nodes
Communication is via message passing
Communication channels are always FIFO
Suppose a distributed system using scalar clocks executes the following rules for updating clocks.
R1: Before executing an event (send, receive, or internal), process pi executes Ci = Ci + d (d > 0)
R2: When process pi receives a message with timestamp Cmsg, it executes the following actions:
1. execute R1;
2. Ci = max (Ci , Cmsg);
3. deliver the message.
What can be inferred about the computed scalar timestamps of the different events occurring in this
system?
Select one:
the event timestamps will be correct
nothing can be concluded due to insufficient information
each event timestamp will depend upon the total number of events occurring in the distributed
system
the event timestamps may be incorrect
The time required to execute a program using a single processor is 500 nanoseconds. The same
program can be executed on a parallel system using 10 identical processors in 20 nanoseconds.
Calculate the speedup. You do not have to consider any form of communication latency.
Select one:
25
26
0.04
0.03
Consider the space time diagram shown in the figure below containing 3 processes, p1, p2 and p3.
Which of the following is true?
Select one:
e33 and e21e12 are concurrent events
e22e22 and e43e34 are concurrent events
e13e31 and e51e15 are concurrent events
e12e21 and e43e34 are concurrent events
For a distributed system consisting of 20 processes, the vector clocks will satisfy the strong
consistency property if the vector timestamps are at least of size
Select one:
19
20
17
18