COMP3270 Assignment 1 Solution

Empirical analysis of algorithms involves implementing, running and then analyzing the run-time data collected against theoretical predictions. This homework asks you to implement, and theoretically and empirically compute the complexities of algorithms with different orders of complexity to solve the problem of Maximum Sum Contiguous Subvector defined as follows:


Requirements:
1. Implement the provided algorithms of different complexity orders to solve this problem. The implementation should be faithful to the algorithms provided in this homework; use the same variable names; if you turn in code that implements different algorithms, perhaps you find on the web, then you will get a zero.
2. Calculate T(n) and the order of complexity of each algorithm in the big-Oh or Theta notation using any of the methods we discussed in class. (a) Show your calculations in the provided tables, then (b) determine and state the polynomial T(n) and (c) the complexity order of the algorithm. Incomplete answers to this part will get zero, not a partial grade.
4. Write a main program that carries out the following tasks, one after the other:
5. First, the main program should read from a file named “phw_input.txt” containing 10 comma-delimited integers in the first line, create an array containing these 10 integers, and run each of the algorithms on that input array, and print out the answer produced by each on the console as follows: "algorithm-1: <answer>; algorithm-2:<answer>; algorithm-3:<answer>; algorithm-4:<answer> where <answer> is the MSCS as determined by each of the algorithms.
6. Next, create 19 integer sequences of length 10,15,20,25,……90,95,100, containing randomly generated negative, zero and positive integers, and store these in 19 arrays of size 10,15,…,95,100: A1-A19.
9. Your main program should write one text line of algorithm and complexity order titles separated by commas (e.g., "algorithm-1,algorithm-2,algorithm-3,algorithm-4,T1(n),T2(n),T3(n), T4(n)"), followed by the above matrix also in comma-delimited format (19 lines of 8 integers separated by commas) to a file called "yourname_phw_output.txt".
10. Open yourname_phw_output.txt with a spreadsheet and produce a labeled graph with 10-100 on the xaxis and 8 curves showing the actual time taken and predicted time (the complexity order) for each algorithm. Label the curves appropriately.

SUBMISSION INSTRUCTIONS
Your submission must include:
1. Source code that is properly commented (if you reuse code fragments from another source such as the text, web site, etc., clearly identify the fragments and their source in comments) including all procedures, functions, classes, etc. and the main program - in short everything we need to compile and run it.
2. A doc or pdf file with:
a. Details of the complexity order calculation as shown by filled tables from p.4-5 of this homework.
• Include all files as a single zipped attachment.
• Include in your submission a README file that should contain your name, the names of all files in the zipped archive, an explanation of how you compiled your program (what IDE or command line compilation command for the compiler you used), and the following certification statement (verbatim): “I certify that I wrote the code I am submitting. I did not copy whole or parts of it from another student or have another person write the code for me. Any code I am reusing in my program is clearly marked as such with its source clearly identified in comments.” Without this certification, your grade will be zero.



GRADING POLICY
The homework will be graded out of a maximum of 100 points. The minimum requirement is to turn in everything asked for. If you do not meet this requirement, you will get 0 points. If you do, your grade will be determined as follows:
8 points for correct complexity order calculation of each algorithm: total 32 points max.
10 points for the graph and 8 points for its explanation: total 18 points max.
If your source does not compile, you will get 0 points out of the remaining 50 points.
If the source compiles correctly but the executable does not run or crashes, you will get 5 points.
If the executable runs, but produces no output file or completely wrong output, you will get 10 points.
If the output is partially correct, you will get a partial grade higher than 10. If the output is fully correct, you will get an additional 50 points.

Algorithm-1(X : array[P..Q] of integer)
1 maxSoFar = 0
2 for L = P to Q
3 for U = L to Q
4 sum =0
5 for I = L to U
6 sum = sum + X[I]
/* sum now contains the sum of X[L..U] */
7 maxSoFar = max (maxSoFar, sum)
8 return maxSoFar

Algorithm-2(X : array[P..Q] of integer)
1 maxSoFar = 0
2 for L = P to Q
3 sum =0
4 for U = L to Q
5 sum = sum + X[U]
/* sum now contains the sum of X[L..U] */
6 maxSoFar = max(maxSoFar,sum)
7 return maxSoFar

Algorithm-3
recursive function MaxSum(X[L..U]: array of integer, L, U: integer)
1 if L > U then
return 0 /* zero- element vector */
2 if L=U then
return max(0,X[L]) /* one-element vector */
3 M = (L+U)/2 /* A is X[L..M], B is X[M+1..U] */
/* Find max crossing to left */
4 sum = 0; maxToLeft =0
5 for I = M downto L do
6 sum =sum+X[I]
7 maxToLeft = max(maxToLeft,sum)
/* Find max crossing to right */
8 sum=0; maxToRight=0
9 for I = M+1 to U
10 sum=sum+X[I]
11 maxToRight = max(maxToRight, sum)
12 maxCrossing = maxToLeft + maxToRight

13 maxInA = maxSum(X, L, M)
14 maxInB = maxSum(X,M+1,U)
15 return max(maxCrossing, maxInA, maxInB)

Algorithm-4(X : array[P..Q] of integer)
1 maxSoFar = 0
2 maxEndingHere= 0
3 for I = P to Q
4 maxEndingHere = max(0, maxEndingHere + X[I])
5 maxSoFar = max(maxSoFar, maxEndingHere)
6 return maxSoFar





Algorithm-1
Step Cost of each execution Total # of times executed
1
2
3
4
5
6
7
8
Multiply col.1 with col.2, add across rows and simplify
T1(n) =

Algorithm-2
Step Cost of each execution Total # of times executed
1
2
3
4
5
6
7
Multiply col.1 with col.2, add across rows and simplify
T2(n) =


Algorithm-3
Step Cost of each execution Total # of times executed in any single recursive call
1
2
Steps executed when the input is a base case:
First recurrence relation: T(n=1 or n=0) =
3
4
5
6
7
8
9
10
11
12
13 (cost excluding the recursive call)
14 (cost excluding the recursive call)
15
Steps executed when input is NOT a base case:
Second recurrence relation: T(n>1) =
Simplified second recurrence relation (ignore the constant term): T(n>1) =
Solve the two recurrence relations using any method (recommended method is the Recursion Tree). Show your work below:



T3(n) =

Algorithm-4
Step Cost of each execution Total # of times executed
1
2
3
4
5
6
Multiply col.1 with col.2, add across rows and simplify
T4(n) =