Description
Assignment
Imagine a virtual world in which all that exists are strings of characters from the set
{ A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, _, , ’ }
(The ‘_’ represents the space character.) Strings in this world can reproduce new strings and
die if they are not fit enough. You will evolve strings in this world until they spell your name. To
do this you will create a Genome class which will contain a list of characters from the above set
representing a string in your world, and you will create a Population class which will contain a
list of Genomes representing all the strings in your world.
Your Genome class must:
● have some internal representation of the string of characters.
● initialize a new string to the default value ‘A’.
● be able to mutate by:
○ possibly adding a new charactersomewhere in the string.
○ possibly deleting a randomly selected characterfrom the string.
○ possibly changing a characterin the string to a different value.
● be able to crossover with another genome:
○ given two Genomes create a third that is a combination of the two.
● be able to measure Genome fitness:
○ using one of the two zerobased fitnessmethods listed here:
■ calculate how close the string in the Genome is from your name using the
simple method detailed below.
■ (Optional) calculate how close the string in the Genome is from your
name using the Levenshtein editdistance.
● display:
○ output the string and its fitness in an easy to read format.
Your Population class must:
● maintain a list of Genomes representing the current population.
● initialize the population with a fixed number of default Genomes.
● update the list of Genomes every breeding cycle by:
○ removing the leastfit members of the population.
○ mutating or breeding the mostfit members of the population.
○ Note:Because we are using a zerobased fitness the “most fit” member of the
population has the lowest fitness score not the highest.
● display the entire population.
● display the mostfit individual in the population.
The Main class is a controller and will:
● instantiate the Population class.
○ Use 100 genomes and a mutation rate of 0.05.
● call day() from the Population class until the fitness of the most fit genome is zero.
● output simulation progress.
● output runtime statistics.
Formal Specifications
Your simulation will implement the Genome class according to this interface:
● String target a data element that is initialized to your name.
● Genome(double mutationRate) a constructor that initializes a Genome with value ‘A’
and assigns the internal mutation rate. The mutationRate must be between zero and
one.
● Genome(Genome gene) a copy constructor that initializes a Genome with the same
values as the input gene.
● void mutate() this function mutates the string in this Genome using the following rules:
○ with mutationRate chance add a randomly selected character to a randomly
selected position in the string.
○ with mutationRate chance delete a single character from a randomly selected
position of the string but do this only if the string has length at least 2.
○ for each character in the string:
■ with mutationRate chance the character is replaced by a randomly
selected character.
● void crossover(Genome other) this function will update the current Genome by crossing
it over with other.
○ Create the new list by following these steps for each index in the string starting at
the first index:
■ Randomly choose one of the two parent strings.
■ If the parent string has a character at this index (i.e. it is long enough)
copy that character into the new list. Otherwise end the new list here.
● Integer fitness() returns the fitness of the Genome calculated using the following
algorithm:
○ Let n be the length of the current string. Let m be the length of the target string.
○ Let l be the max(n, m).
○ Let f be initialized to |m n|.
○ For each character position 1 ≤ i ≤ l add one to f if the character in the current
string is different from the character in the target string (or if one of the two
characters does not exist). Otherwise add nothing to f.
○ Return f.
● (Optional) Integer fitness() instead of the algorithm above use the WagnerFischer
algorithm for calculating Levenshtein edit distance:
○ Let n be the length of the current string. Let m be the length of the target string.
○ Create an (n + 1) x (m + 1) matrix D initialized with 0s.
○ Fill the first row of the matrix with the column indices and fill the first column of
the matrix with the row indices.
○ Implement this nested loop to fill in the rest of the matrix.
forrowfrom1ton
forcolumnfrom1tom
if(current[row1]==target[column1])D[i,j]=D[i1,j1]
elseD[i,j]=min(D[i1,j]+1,D[i,j1]+1,D[i1,j1]+1)
○ Return the value stored in D[n,m] + (abs(n m) + 1) / 2. (Use integer arithmetic.)
● String toString() this function will display the Genome’s character string and fitness in
an easy to read format.
Your simulation will implement the Population class. It must function according to this interface :
● Genome mostFit a data element that is equal to the mostfit Genome in the population.
● void Population(Integer numGenomes, Double mutationRate) a constructor that
initializes a Population with a number of default genomes (see above).
● void day() this function is called every breeding cycle and carries out the following
steps:
○ update mostFit variable to the mostfit Genome in the population. (Remember
this is the genome with the lowest fitness!)
○ delete the leastfit half of the population.
○ create new genomes from the remaining population until the number of genomes
is restored by doing either of the following with equal chance:
■ pick a remaining genome at random and clone it (with the copy
constructor) and mutate the clone.
■ pick a remaining genome at random and clone it and then crossover the
clone with another remaining genome selected at random and then
mutate the result.
You will also provide a Main class for control and testing of your evolutionary algorithm.
● void main(String[] args) this method should instantiate a population and call day() until
the target string is part of the population.
○ The target string has fitness zero so the loop should repeat until the most fit
genome has fitness zero.
○ After each execution of day() output the most fit genome.
○ To measure performance output the number of generations (i.e times day() is
called) and the execution time.
● void testGenome() this method tests the Genome class.
● void testPopulation() this method tests the Population class.
Include any other methods used to test components of your Genome and Population classes.
Hint:Even a slight deviation from the specifications can result in bugs that affect performance.
Make sure you implement these methods exactly as stated above.
Submission
The following files are provided for you:
● trace.txt an example trace of my solution.
You will submit a .zip file containing:
● Genome.java an implementation of the Genome class satisfying the above criteria.
● Population.java an implementation of the Population class satisfying the above criteria.
● Main.java a controller for your evolutionary system that serves to run the evolutionary
simulation and test the components of your code.
Grading Rubric
This assignment is graded out of 25 points but there are 31 points available.
Correctness 15 points
● To get all 15 points your code must evolve my name “CHRISTOPHER PAUL
MARRIOTT” in fewer than 1000 generations and in less than 3 seconds.
● Solutions that evolve my name in more than 1000 but at most 10000 generations will be
deducted 4 points.
● Solutions that evolve my name in more than 10000 but less than 100000 generations will
be deducted 8 points..
● Solutions that take more than 3 seconds will be deducted 3 points.
● A 0 will be awarded if your solution cannot evolve my name.
● One point is deducted if you do not output the fittest string and its fitness every
generation.
● One point is deducted if you do not output the generation number every generation.
● One point is deducted if you do not output the runtime of your program.
Interface 5 points
● All Genome methods and properties match the interface provided above. One point is
deducted for each mismatch.
● All Population methods match the interface provided above. One point is deducted for
each mismatch.
Testing 4 points
● All Genome methods are tested. Points are deducted for missing tests or inadequate
tests.
● All Population methods are tested. Points are deducted for missing tests or inadequate
tests.
Miscellaneous 4 points
● All four points are awarded automatically with the following exceptions.
● One point is deducted if you work in a team of two.
● One point is deducted if your submission is late.
● One point is deducted if you resubmit after your assignment is graded.
● One point is deducted if your submission is not in the correct format (i.e. not in a ZIP,
you submit .class files instead of .java, you submit code that needs to be altered to work,
etc.)
(Optional)WagnerFischer Algorithm 3 points
● All three points are awarded if you implement the optional fitness function using the
WagnerFischer Algorithm.
Tips for maximizing your grade:
● Make sure your classes match the interface structure exactly. I will use my own
controller (Main.java) and test files on your code and it should work without changes. Do
not change the method name (even capitalization), return type, argument number, type,
and order. Make sure all parts of the interface are implemented.
● Only zip up the .java files. If you use eclipse these are found in the “src” directory, not
the “bin” directory. I can do nothing with the .class files.
● All program components should be in the default package. If you use a different
package it increases the difficulty of grading and thus affects your grade.
● Place your name in the comments at the top of every file. If you are a group of two make
sure both names appear clearly in these comments.
