Week 8: SELF-PACED READING

Question 1

_ is the world’s largest coding community for children and a coding language with a simple visual interface design to gentle introduction of programming concepts.

Answer 1

Scratch

Question 2

_ is an increasingly popular choice as a first programming language in computer science curricula.

Answer 2

Python

Question 3

In addition to the three-tier model, other types of distributed computing include:

Answer 3

• Client-server architectures. These use smart clients that contact a server for data, and then format and display that data to the user.
• N-tier system architectures. Typically used in application servers, these architectures use web applications to forward requests to other enterprise services.
• Peer-to-peer architectures. These divide all responsibilities among all peer computers, which can serve as clients or servers.

Question 4

_ is a general term for anything that involves delivering hosted services over the internet.

Answer 4

Cloud computing

Question 5

_ is a special case of a more common mechanism called a multicast in which a value is sent to a subset of nodes.

Answer 5

Broadcasting

✓ It has one sender and multiple receivers.

Question 6

_ is the collection of information from several sources into one sink (as in the fan-in tree)

Answer 6

Convergecast

✓ is a fundamental operation of distributed systems, and is commonly used in sensor networks in which the information from several sensors must be aggregated into a node.
✓ the idea is similar to a multicast, in that a tree is employed, this time to move information from the leaves to the root.

Question 7

_ has one/more senders and one/more recipients participate in data transfer traffic.

Answer 7

Multicasting

✓ It has one or more senders and multiple receivers.

Question 8

The _ is a package that supports spawning processing using API similar to the threading module.

Answer 8

tree

Question 9

The _ is an important interconnection network in modern computing systems.

Answer 9

bus

Question 10

_ have additional circuitry via which the gate outputs can be enabled or disabled.

Answer 10

Tri-state gates

Question 11

A _ is a group of computers connected through wires, optical fibres, or optical links so that various devices can interact with each other through a network.

Answer 11

Computer Network

• The aim of the computer network is the sharing of resources among various devices.
• In the case of computer network technology, several types of networks vary from simple to complex level

Question 12

_ defines the structure of the network of how all the components are interconnected to each other.

Answer 12

Topology

Question 13

Two types of topology

Answer 13

physical and logical topology

Question 14

_ is the geometric representation of all the nodes in a network.

Answer 14

Physical topology

Question 15

_ refers to the way data is transmitted from one node to another on a network.

Answer 15

Logical Topology

Question 16

_ is designed in such a way that all the stations are connected through a single cable known as a backbone cable.

Answer 16

BUS TOPOLOGY

• The configuration of a bus topology is quite simple as compared to other topologies.
• The backbone cable is considered as a “single lane” through which the message is broadcast to all the stations.
• The most common access method of the bus topologies is CSMA (Carrier Sense Multiple Access).

Question 17

The most common access method of the bus topologies is _.

Answer 17

CSMA (Carrier Sense Multiple Access)

Question 18

Advantages of bus topology

Answer 18

• Low-cost cable
• Moderate Data Speeds
• Familiar Technology
• Limited Failure

Question 19

It is a media access control used to control the data flow so that data integrity is maintained, i.e., the packets do not get lost.

Answer 19

CSMA (Carrier Sense Multiple Access)

Question 20

There are two alternative ways of handling the problems that occur when two nodes send messages simultaneously.

Answer 20

• CSMA CD: CSMA CD (Collision detection) is an access method used to detect the collision. Once the collision is detected, the sender will stop transmitting the data. Therefore, it works on “recovery after the collision”.
• CSMA CA: CSMA CA (Collision Avoidance) is an access method used to avoid collision by checking whether the transmission media is busy or not. If busy, then the sender waits until the media becomes idle. This technique effectively reduces the possibility of a collision. It does not work on “recovery after the collision”.

Question 21

_ is an access method used to detect the collision. Once the collision is detected, the sender will stop transmitting the data. Therefore, it works on “recovery after the collision”.

Answer 21

CSMA CD (Collision detection)

Question 22

_ is an access method used to avoid collision by checking whether the transmission media is busy or not. If busy, then the sender waits until the media becomes idle. This technique effectively reduces the possibility of a collision. It does not work on “recovery after the collision”.

Answer 22

CSMA CA (Collision Avoidance)

Question 23

_ is like a bus topology, but with connected ends.

Answer 23

RING TOPOLOGY

• The node that receives the message from the previous computer will retransmit to the next node.
• The data flows in one direction, i.e., it is unidirectional.
• The data flows in a single loop continuously known as an endless loop.
• It has no terminated ends, i.e., each node is connected to another node and has no termination point.
• The data in a ring topology flow in a clockwise direction.
• The most common access method of the ring topology is token passing.

Question 24

It is a network access method in which a token is passed from one node to another node.

Answer 24

Token passing

Question 25

It is a frame that circulates the network.

Answer 25

Token

Question 26

The message-passing paradigm is a powerful concept for problem-solving from small clusters to extreme-scale supercomputers.

Answer 26

THE MESSAGE-PASSING CONCEPT ## Footnote * Is a standardized interface for exchanging messages between multiple computers running a parallel program across

Question 27

Two main communication mechanisms are:

Answer 27

1. **Point-to-point communication:** allows pairwise data exchanges, while a collective communication coordinates data exchange and synchronization across many processes in a single operation. 2. **Collective communications:** Communication groups, called communicators, can be defined in order to partition the possible destinations that processes can send to. Only processes that belong to a communicator can send to other processes in that communicator. This is a very useful concept when multiple MPI instances need to be used simultaneously.

Question 28

Allows pairwise data exchanges, while a collective communication coordinates data exchange and synchronization across many processes in a single operation.

Answer 28

Point-to-point communication

Question 29

Communication groups, called communicators, can be defined in order to partition the possible destinations that processes can send to. Only processes that belong to a communicator can send to other processes in that communicator. This is a very useful concept when multiple MPI instances need to be used simultaneously.

Answer 29

Collective communications ## Footnote MPI defines this communicator as MPI _ COMM _ WORLD, and in practice, many applications use MPI _ COMM _ WORLD as their communicator. (NO SPACE IN UNDERSCORE)

Question 30

One of the most important operations for a distributed process computation is the ability to **synchronize all of the processes at a given point** during execution. Similarly to shared memory threading models, a **barrier operation** forces all of the processes to report that they have arrived at the barrier point in the code. After all of the processes have arrived at the barrier, the processes are then permitted to continue execution.

Answer 30

Noted

Question 31

One way to reduce the communication time.

Answer 31

Cloud Computing

Question 32

A synchronization operation that ensures all processes reach a common synchronization point before proceeding.

Answer 32

Barrier

Question 33

Communication routines that involve all processes

Answer 33

Collective operation

Question 34

In multiprocessing, processes are spawned by creating a process object that calls its _

Answer 34

start() method

Question 35

The barrier is called a _ because all processes, rather than a single send-receive pair, participate.

Answer 35

collective operation

Question 36

Types of collective operations

Answer 36

* **Broadcast** (one to all) * **Gather** (get data from all other processes) * **Scatter** (sends data from one task to all other tasks in a group) * **Reduce** (combines values from all processes into a single value, e.g., an addition) * **All-to-all** (every process broadcast).