C++ Question

You need to develop the decoder for a new compression algorithm to evaluate the effectiveness of Elias-Gamma encoding for larger integer values. The proposed compression algorithm works as follows:

1. Determine the frequency of symbols in the message.

2. Sort the alphabet symbols in descending order based on their frequency. If two or more symbols have the same frequency, sort them according to lexicographical order (ascending based on ASCII value).

3. Create the encoded message by appending the positions of the symbols (based on the sorted alphabet) in the original message. Since Elias-Gamma encoding is used to represent the positions, the values for the positions start from one.

Given the following original message: AACABDDADABC

The alphabet is sorted as A, D, B, and C, and the positions in the encoded message are: 1, 2, 4, 8, 10, 6, 7, 9, 5, 11, 3, and 12 (represented as Elias-Gamma codes).

Your decoder takes the following information as input from the standard input (STDIN):

1. An integer representing the alphabet size (m).

2. m symbols. Each symbol is represented by a single character and an integer value indicating its frequency.

3. A binary string with positions encoded using Elias-Gamma code. The position values are stored according to the order of symbols in the sorted alphabet.

For this assignment, you will create a multithreaded program to find the positions of the symbols in the original message, reconstruct the original message (based on the encoded message), and determine the number of bits required to represent the positions using Elias-Gamma encoding.

Given the following input:

4
A 5
C 2
B 2
D 3
10100010000010000001010001100011100010010010100010110110001100

The expected output is:

Symbol: A, Frequency: 5
Positions: 0 1 3 7 9
Bits to represent the position(s): 23

Symbol: D, Frequency: 3
Positions: 5 6 8
Bits to represent the position(s): 17

Symbol: B, Frequency: 2
Positions: 4 10
Bits to represent the position(s): 12

Symbol: C, Frequency: 2
Positions: 2 11
Bits to represent the position(s): 10

Decoded message: AACABDDADABC

Process:

Your solution must execute the following steps:

• Read the input lines from STDIN.

• • Create m POSIX threads (where m is the alphabet size). Each child thread performs the following tasks:

– Receives the encoded message, the symbol to decode, and the memory location to store the decoding results.

– Determines the positions of the assigned symbol in the original message.

– Calculates the number of bits used to represent the symbol’s position using Elias Gamma encoding.

– Stores the assigned symbol’s information in a memory location accessible by the main thread.

– Stores the assigned symbol, using the determined positions, into the memory address shared with the main thread that contains the decoded message.

• Print the information for each symbol to STDOUT (sorted according to the compression algorithm rules).

• Print the decoded message.

Notes:

• The position values for the symbols must start from one (not from zero), because Elias Gamma encoding can only represent positive integers starting from one.

• You can safely assume that the input will always be in the proper format.

• You must use the output statement format shown in the example above.

• You can define additional functions if needed.

• You must take full advantage of multithreading.

• You must present code that is readable and has comments explaining the logic of your solution. A 10% penalty will be applied to submissions that do not follow this guideline.

• You cannot use global variables. A 100% penalty will be applied to submissions using global variables.

• Not using multiple POSIX threads (the pthread.h library) to implement your solution will result in a 100% penalty. DO NOT USE THE THREAD LIBRARY FROM C++.

• A penalty of 100% will be applied to solutions that do not compile.

• A penalty of 100% will be applied to solutions that hardcode the output.

Assignment rubric:

• Correct output: 10 points per test case (20 points total).

• Correct implementation of the thread function: 30 points.

• Taking full advantage of multithreading (no pthread_join or sleep in the same loop as pthread_create): 30 points.

• Creating the correct number of threads: 10 points.

• Having clean and commented code: 10 points.

Penalties:

1. Presenting a solution that does not compile: -100 points.

2. Not using POSIX threads: -100 points.

3. Hardcoding the output: -100 points.

4. Using global variables: -100 points.

5. Using AI tools without following the rules stated in the syllabus: -100 points.

   the rules in the syllabus mention that you are only allowed to use AI tools to help understand why your solution isn’t working, and you must include a comment in the AI-generated code section explaining the problem the tool addressed.

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