1
GATE CSE 2021 Set 2
MCQ (Single Correct Answer)
+2
-0.66

Consider the following ANSI C code segment:

z = x + 3 + y -> f1 + y -> f2;

for (i = 0; i < 200; i = i + 2){

if (z > i) {

P = p + x + 3;

q = q + y -> f2;

} else {

p = p + y -> f2;

q = q + x + 3;

}

}

Assume that the variable y points to a struct (allocated on the heap) containing two fields f1 and f2, and the local variables x, y, z, p, g, and i are allotted registers. Common sub-expression elimination (CSE) optimization is applied on the code. The number of addition and dereference operations (of the form y -> f1 or y -> f2 ) in the optimized code, respectively, are:  

A
203 and 2
B
403 and 102
C
303 and 102
D
303 and 2
2
GATE CSE 2021 Set 2
MCQ (Single Correct Answer)
+2
-0.66

For a statement S in a program, in the context of liveness analysis, the following sets are defined:

USE(S): the set of variables used in S

IN(S): the set of variables that are live at the entry of S

OUT(S): the set of variables that are live at the exit of S

Consider a basic block that consists of two statements, S1 followed by S2.

Which one of the following statements is correct?

A
OUT(S1) = USE(S1) ∪ IN(S2)
B
OUT(S1) = IN(S2)
C
OUT(S1) = IN(S1) ∪ USE(S1)
D
OUT(S1) = IN(S2) ∪ USE(S2)
3
GATE CSE 2021 Set 2
MCQ (Single Correct Answer)
+1
-0.33
Consider the three-way handshake mechanism followed during TCP connection establishment between hosts P and Q. Let X and Y be two random 32-bit starting sequence numbers chosen by P and Q respectively. Suppose P sends a TCP connection request message to Q with a TCP segment having SYN bit = 1, SEQ number = X, and ACK bit = 0. Suppose Q accepts the connection request. Which one of the following choices represents the information present in the TCP segment header that is sent by Q to P?
A
SYN bit = 0, SEQ number = X + 1, ACK bit = 0, ACK number = Y, FIN bit = 1
B
SYN bit = 1, SEQ number = X + 1, ACK bit = 0, ACK number = Y, FIN bit = 0
C
SYN bit = 1, SEQ number = Y, ACK bit = 1, ACK number = X, FIN bit = 0
D
SYN bit = 1, SEQ number = Y, ACK bit = 1, ACK number = X + 1, FIN bit = 0
4
GATE CSE 2021 Set 2
MCQ (More than One Correct Answer)
+2
-0

Consider a computer network using the distance vector routing algorithm in its network layer. The partial topology of the network is as shown below.

GATE CSE 2021 Set 2 Computer Networks - Network Layer Question 10 English

The objective is to find the shortest-cost path from the router R to routers P and Q. Assume that R does not initially know the shortest routes to P and Q. Assume that R has three neighbouring routers denoted as X, Y, and Z. During one iteration, R measures its distance to its neighbours X, Y, and Z as 3, 2, and 5, respectively. Router R gets routing vectors from its neighbours that indicate that the distance to router P from routers X, Y, and Z are 7, 6, and 5, respectively. The routing vector also indicates that the distance to router Q from routers X, Y, and Z are 4, 6, and 8, respectively. Which of the following statement(s) is/are correct with respect to the new routing table of R, after updation during this iteration ? 

A
The next hop router for a packet from R to P is Y.
B
The distance from R to Q will be stored as 7
C
The next hop router for a packet from R to Q is Z.
D
The distance from R to P will be stored as 10.
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