@ -0,0 +1,484 @@ | |||||
<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script> | |||||
<script | |||||
src="https://code.jquery.com/jquery-3.3.1.slim.min.js" | |||||
integrity="sha256-3edrmyuQ0w65f8gfBsqowzjJe2iM6n0nKciPUp8y+7E=" | |||||
crossorigin="anonymous"> | |||||
</script> | |||||
<script> | |||||
class Gene | |||||
{ | |||||
/** | |||||
* Constructs a new Gene to store in a chromosome. | |||||
* @param min minimum value that this gene can store | |||||
* @param max value this gene can possibly be | |||||
* @param value normalized value | |||||
*/ | |||||
constructor(min, max, value) | |||||
{ | |||||
this.min = min; | |||||
this.max = max; | |||||
this.value = value; | |||||
} | |||||
/** | |||||
* De-normalizes the value of the gene | |||||
* @returns {*} | |||||
*/ | |||||
getRealValue() | |||||
{ | |||||
return (this.max - this.min) * this.value + this.min; | |||||
} | |||||
getValue() | |||||
{ | |||||
return this.value; | |||||
} | |||||
setValue(val) | |||||
{ | |||||
this.value = val; | |||||
} | |||||
makeClone() | |||||
{ | |||||
return new Gene(this.min, this.max, this.value); | |||||
} | |||||
makeRandomGene() | |||||
{ | |||||
return new Gene(this.min, this.max, Math.random()); | |||||
} | |||||
} | |||||
class Chromosome | |||||
{ | |||||
/** | |||||
* Constructs a chromosome by making a copy of | |||||
* a list of genes. | |||||
* @param geneArray | |||||
*/ | |||||
constructor(geneArray) | |||||
{ | |||||
this.genes = []; | |||||
for(let i = 0; i < geneArray.length; i++) | |||||
{ | |||||
this.genes.push(geneArray[i].makeClone()); | |||||
} | |||||
} | |||||
getGenes() | |||||
{ | |||||
return this.genes; | |||||
} | |||||
/** | |||||
* Mutates a random gene. | |||||
*/ | |||||
mutate() | |||||
{ | |||||
this.genes[Math.round(Math.random() * (this.genes.length-1))].setValue(Math.random()); | |||||
} | |||||
/** | |||||
* Creates a totally new chromosome with same | |||||
* genetic structure as this chromosome but different | |||||
* values. | |||||
* @returns {Chromosome} | |||||
*/ | |||||
createRandomChromosome() | |||||
{ | |||||
let geneAr = []; | |||||
for(let i = 0; i < this.genes.length; i++) | |||||
{ | |||||
geneAr.push(this.genes[i].makeRandomGene()); | |||||
} | |||||
return new Chromosome(geneAr); | |||||
} | |||||
} | |||||
/** | |||||
* Mates two chromosomes using the blending method | |||||
* and returns a list of 2 offspring. | |||||
* @param father | |||||
* @param mother | |||||
* @returns {Chromosome[]} | |||||
*/ | |||||
const breed = function(father, mother) | |||||
{ | |||||
let son = new Chromosome(father.getGenes()); | |||||
let daughter = new Chromosome(mother.getGenes()); | |||||
for(let i = 0;i < son.getGenes().length; i++) | |||||
{ | |||||
let blendCoef = Math.random(); | |||||
blendGene(son.getGenes()[i], daughter.getGenes()[i], blendCoef); | |||||
} | |||||
return [son, daughter]; | |||||
}; | |||||
/** | |||||
* Blends two genes together based on a random blend | |||||
* coefficient. | |||||
**/ | |||||
const blendGene = function(gene1, gene2, blendCoef) | |||||
{ | |||||
let value1 = (blendCoef * gene1.getValue()) + | |||||
(gene2.getValue() * (1- blendCoef)); | |||||
let value2 = ((1-blendCoef) * gene1.getValue()) + | |||||
(gene2.getValue() * blendCoef); | |||||
gene1.setValue(value1); | |||||
gene2.setValue(value2); | |||||
}; | |||||
/** | |||||
* Helper function to sort an array | |||||
* | |||||
* @param prop name of JSON property to sort by | |||||
* @returns {function(*, *): number} | |||||
*/ | |||||
function predicateBy(prop) | |||||
{ | |||||
return function(a,b) | |||||
{ | |||||
var result; | |||||
if(a[prop] > b[prop]) | |||||
{ | |||||
result = 1; | |||||
} | |||||
else if(a[prop] < b[prop]) | |||||
{ | |||||
result = -1; | |||||
} | |||||
return result; | |||||
} | |||||
} | |||||
/** | |||||
* Function which computes the fitness of everyone in the | |||||
* population and returns the most fit survivors. Method | |||||
* known as elitism. | |||||
* | |||||
* @param population | |||||
* @param keepNumber | |||||
* @param fitnessFunction | |||||
* @returns {{average: number, | |||||
* survivors: Array, bestFit: Chromosome }} | |||||
*/ | |||||
const naturalSelection = function(population, keepNumber, fitnessFunction) | |||||
{ | |||||
let fitnessArray = []; | |||||
let total = 0; | |||||
for(let i = 0; i < population.length; i++) | |||||
{ | |||||
const fitness = fitnessFunction(population[i]); | |||||
fitnessArray.push({fit:fitness, chrom: population[i]}); | |||||
total+= fitness; | |||||
} | |||||
fitnessArray.sort(predicateBy("fit")); | |||||
let survivors = []; | |||||
let bestFitness = fitnessArray[0].fit; | |||||
let bestChromosome = fitnessArray[0].chrom; | |||||
for(let i = 0; i < keepNumber; i++) | |||||
{ | |||||
survivors.push(fitnessArray[i].chrom); | |||||
} | |||||
return {average: total/population.length, survivors: survivors, bestFit: bestFitness, bestChrom: bestChromosome}; | |||||
}; | |||||
/** | |||||
* Randomly everyone in the population | |||||
* | |||||
* @param population | |||||
* @param desiredPopulationSize | |||||
*/ | |||||
const matePopulation = function(population, desiredPopulationSize) | |||||
{ | |||||
const originalLength = population.length; | |||||
while(population.length < desiredPopulationSize) | |||||
{ | |||||
let index1 = Math.round(Math.random() * (originalLength-1)); | |||||
let index2 = Math.round(Math.random() * (originalLength-1)); | |||||
if(index1 !== index2) | |||||
{ | |||||
const babies = breed(population[index1], population[index2]); | |||||
population.push(babies[0]); | |||||
population.push(babies[1]); | |||||
} | |||||
} | |||||
}; | |||||
/** | |||||
* Randomly mutates the population | |||||
**/ | |||||
const mutatePopulation = function(population, mutatePercentage) | |||||
{ | |||||
if(population.length >= 2) | |||||
{ | |||||
let mutations = mutatePercentage * | |||||
population.length * | |||||
population[0].getGenes().length; | |||||
for(let i = 0; i < mutations; i++) | |||||
{ | |||||
population[i].mutate(); | |||||
} | |||||
} | |||||
else | |||||
{ | |||||
console.log("Error, population too small to mutate"); | |||||
} | |||||
}; | |||||
/** | |||||
* Introduces x random chromosomes to the population. | |||||
* @param population | |||||
* @param immigrationSize | |||||
*/ | |||||
const newBlood = function(population, immigrationSize) | |||||
{ | |||||
for(let i = 0; i < immigrationSize; i++) | |||||
{ | |||||
let geneticChromosome = population[0]; | |||||
population.push(geneticChromosome.createRandomChromosome()); | |||||
} | |||||
}; | |||||
let costx = Math.random() * 10; | |||||
let costy = Math.random() * 10; | |||||
/** Defines the cost as the "distance" to a 2-d point. | |||||
* @param chromosome | |||||
* @returns {number} | |||||
*/ | |||||
const basicCostFunction = function(chromosome) | |||||
{ | |||||
return Math.abs(chromosome.getGenes()[0].getRealValue() - costx) + | |||||
Math.abs(chromosome.getGenes()[1].getRealValue() - costy); | |||||
}; | |||||
/** | |||||
* Creates a totally random population based on a desired size | |||||
* and a prototypical chromosome. | |||||
* | |||||
* @param geneticChromosome | |||||
* @param populationSize | |||||
* @returns {Array} | |||||
*/ | |||||
const createRandomPopulation = function(geneticChromosome, populationSize) | |||||
{ | |||||
let population = []; | |||||
for(let i = 0; i < populationSize; i++) | |||||
{ | |||||
population.push(geneticChromosome.createRandomChromosome()); | |||||
} | |||||
return population; | |||||
}; | |||||
/** | |||||
* Runs the genetic algorithm by going through the processes of | |||||
* natural selection, mutation, mating, and immigrations. This | |||||
* process will continue until an adequately performing chromosome | |||||
* is found or a generation threshold is passed. | |||||
* | |||||
* @param geneticChromosome Prototypical chromosome: used so algo knows | |||||
* what the dna of the population looks like. | |||||
* @param costFunction Function which defines how bad a Chromosome is | |||||
* @param populationSize Desired population size for population | |||||
* @param maxGenerations Cut off level for number of generations to run | |||||
* @param desiredCost Sufficient cost to terminate program at | |||||
* @param mutationRate Number between [0,1] representing proportion of genes | |||||
* to mutate each generation | |||||
* @param keepNumber Number of Organisms which survive each generation | |||||
* @param newBloodNumber Number of random immigrants to introduce into | |||||
* the population each generation. | |||||
* @returns {*} | |||||
*/ | |||||
const runGeneticOptimization = function(geneticChromosome, costFunction, | |||||
populationSize, maxGenerations, | |||||
desiredCost, mutationRate, keepNumber, | |||||
newBloodNumber) | |||||
{ | |||||
let population = createRandomPopulation(geneticChromosome, populationSize); | |||||
let generation = 0; | |||||
let bestCost = Number.MAX_VALUE; | |||||
let bestChromosome = geneticChromosome; | |||||
do | |||||
{ | |||||
matePopulation(population, populationSize); | |||||
newBlood(population, newBloodNumber); | |||||
mutatePopulation(population, mutationRate); | |||||
let generationResult = naturalSelection(population, keepNumber, costFunction); | |||||
if(bestCost > generationResult.bestFit) | |||||
{ | |||||
bestChromosome = generationResult.bestChrom; | |||||
bestCost = generationResult.bestFit; | |||||
} | |||||
population = generationResult.survivors; | |||||
generation++; | |||||
console.log("Generation " + generation + " Best Cost: " + bestCost); | |||||
}while(generation < maxGenerations && bestCost > desiredCost); | |||||
return bestChromosome; | |||||
}; | |||||
/** | |||||
* Ugly globals used to keep track of population state for the graph. | |||||
*/ | |||||
let genericChromosomeG, costFunctionG, | |||||
populationSizeG, maxGenerationsG, | |||||
desiredCostG, mutationRateG, keepNumberG, | |||||
newBloodNumberG, populationG, generationG, | |||||
bestCostG = Number.MAX_VALUE, bestChromosomeG = genericChromosomeG; | |||||
const runGeneticOptimizationForGraph = function() | |||||
{ | |||||
let generationResult = naturalSelection(populationG, keepNumberG, costFunctionG); | |||||
stats.push([generationG, generationResult.bestFit, generationResult.average]); | |||||
if(bestCostG > generationResult.bestFit) | |||||
{ | |||||
bestChromosomeG = generationResult.bestChrom; | |||||
bestCostG = generationResult.bestFit; | |||||
} | |||||
populationG = generationResult.survivors; | |||||
generationG++; | |||||
console.log("Generation " + generationG + " Best Cost: " + bestCostG); | |||||
console.log(generationResult); | |||||
matePopulation(populationG, populationSizeG); | |||||
newBlood(populationG, newBloodNumberG); | |||||
mutatePopulation(populationG, mutationRateG); | |||||
createGraph(); | |||||
}; | |||||
let stats = []; | |||||
const createGraph = function() | |||||
{ | |||||
var dataPoints = []; | |||||
console.log(dataPoints); | |||||
var data = new google.visualization.DataTable(); | |||||
data.addColumn('number', 'Gene 1'); | |||||
data.addColumn('number', 'Gene 2'); | |||||
for(let i = 0; i < populationG.length; i++) | |||||
{ | |||||
data.addRow([populationG[i].getGenes()[0].getRealValue(), | |||||
populationG[i].getGenes()[1].getRealValue()]); | |||||
} | |||||
var options = { | |||||
title: 'Genetic Evolution On Two Genes Generation: ' + generationG, | |||||
hAxis: {title: 'Gene 1', minValue: 0, maxValue: 10}, | |||||
vAxis: {title: 'Gene 2', minValue: 0, maxValue: 10}, | |||||
}; | |||||
var chart = new google.visualization.ScatterChart(document.getElementById('chart_div')); | |||||
chart.draw(data, options); | |||||
//line chart stuff | |||||
var line_data = new google.visualization.DataTable(); | |||||
line_data.addColumn('number', 'Generation'); | |||||
line_data.addColumn('number', 'Best'); | |||||
line_data.addColumn('number', 'Average'); | |||||
line_data.addRows(stats); | |||||
console.log(stats); | |||||
var lineChartOptions = { | |||||
hAxis: { | |||||
title: 'Generation' | |||||
}, | |||||
vAxis: { | |||||
title: 'Cost' | |||||
}, | |||||
colors: ['#AB0D06', '#007329'] | |||||
}; | |||||
var chart = new google.visualization.LineChart(document.getElementById('line_chart')); | |||||
chart.draw(line_data, lineChartOptions); | |||||
}; | |||||
let gene1 = new Gene(1,10,10); | |||||
let gene2 = new Gene(1,10,0.4); | |||||
let geneList = [gene1, gene2]; | |||||
let exampleOrganism = new Chromosome(geneList); | |||||
genericChromosomeG = exampleOrganism; | |||||
costFunctionG = basicCostFunction; | |||||
populationSizeG = 100; | |||||
maxGenerationsG = 30; | |||||
desiredCostG = 0.00001; | |||||
mutationRateG = 0.3; | |||||
keepNumberG = 30; | |||||
newBloodNumberG = 10; | |||||
generationG = 0; | |||||
function verifyForm() | |||||
{ | |||||
if(Number($("#populationSize").val()) <= 1) | |||||
{ | |||||
alert("Population size must be greater than one."); | |||||
return false; | |||||
} | |||||
if(Number($("#mutationRate").val()) > 1 || | |||||
Number($("#mutationRate").val()) < 0) | |||||
{ | |||||
alert("Mutation rate must be between zero and one."); | |||||
return false; | |||||
} | |||||
if(Number($("#survivalSize").val()) < 0) | |||||
{ | |||||
alert("Survival size can't be less than one."); | |||||
return false; | |||||
} | |||||
if(Number($("#newBlood").val()) < 0) | |||||
{ | |||||
alert("New organisms can't be a negative number."); | |||||
return false; | |||||
} | |||||
return true; | |||||
} | |||||
function resetPopulation() | |||||
{ | |||||
if(verifyForm()) | |||||
{ | |||||
stats = []; | |||||
autoRunning = false; | |||||
$("#runAutoOptimizer").val("Auto Run"); | |||||
populationSizeG = $("#populationSize").val(); | |||||
mutationRateG = $("#mutationRate").val(); | |||||
keepNumberG = $("#survivalSize").val(); | |||||
newBloodNumberG = $("#newBlood").val(); | |||||
generationG = 0; | |||||
populationG = createRandomPopulation(genericChromosomeG, populationSizeG); | |||||
createGraph(); | |||||
} | |||||
} | |||||
populationG = createRandomPopulation(genericChromosomeG, populationSizeG); | |||||
window.onload = function (){ | |||||
google.charts.load('current', {packages: ['corechart', 'line']}); | |||||
google.charts.load('current', {'packages':['corechart']}).then(function() | |||||
{ | |||||
createGraph(); | |||||
}) | |||||
}; | |||||
let autoRunning = false; | |||||
function runAutoOptimizer() | |||||
{ | |||||
if(autoRunning === true) | |||||
{ | |||||
runGeneticOptimizationForGraph(); | |||||
setTimeout(runAutoOptimizer, 1000); | |||||
} | |||||
} | |||||
function startStopAutoRun() | |||||
{ | |||||
autoRunning = !autoRunning; | |||||
if(autoRunning) | |||||
{ | |||||
$("#runAutoOptimizer").val("Stop Auto Run"); | |||||
} | |||||
else | |||||
{ | |||||
$("#runAutoOptimizer").val("Resume Auto Run"); | |||||
} | |||||
runAutoOptimizer(); | |||||
} | |||||
</script> | |||||
<div id="chart_div"></div> | |||||
<div id="line_chart"></div> | |||||
<input class='btn btn-primary' id="runOptimizer" onclick='runGeneticOptimizationForGraph()' type="button" value="Next Generation"> | |||||
<input class='btn btn-primary' id="runAutoOptimizer" onclick='startStopAutoRun()' type="button" value="Auto Run"> | |||||
<br> | |||||
<br> | |||||
<div class="card"> | |||||
<div class="card-header"> | |||||
<h2>Population Variables</h2> | |||||
</div> | |||||
<form class="card-body"> | |||||
<div class="row p-2"> | |||||
<div class="col"> | |||||
<label for="populationSize">Population Size</label> | |||||
<input type="text" class="form-control" value="100" id="populationSize" placeholder="Population Size" required> | |||||
</div> | |||||
<div class="col"> | |||||
<label for="populationSize">Survival Size</label> | |||||
<input type="text" class="form-control" value="20" id="survivalSize" placeholder="Survival Size" required> | |||||
</div> | |||||
</div> | |||||
<div class="row p-2"> | |||||
<div class="col"> | |||||
<label for="populationSize">Mutation Rate</label> | |||||
<input type="text" class="form-control" value="0.03" id="mutationRate" placeholder="Mutation Rate" required> | |||||
</div> | |||||
<div class="col"> | |||||
<label for="populationSize">New Organisms Per Generation</label> | |||||
<input type="text" class="form-control" value="5" id="newBlood" placeholder="New Organisms" required> | |||||
</div> | |||||
</div> | |||||
<br> | |||||
<input class='btn btn-primary' id="reset" onclick='resetPopulation()' type="button" value="Reset Population"> | |||||
</form> | |||||
</div> |
@ -0,0 +1,515 @@ | |||||
# Live Simulation | |||||
<customHTML /> | |||||
# Background and Theory | |||||
Since you stumbled upon this article, you might be wondering what the heck genetic algorithms are. | |||||
To put it simply: genetic algorithms employ the same tactics used in natural selection to find an optimal solution to an optimization problem. | |||||
Genetic algorithms are often used in high dimensional problems where the optimal solutions are not apparent. | |||||
Genetic algorithms are commonly used to tune the [hyper-parameters](https://en.wikipedia.org/wiki/Hyperparameter) of a program. | |||||
However, this algorithm can be used in any scenario where you have a function which defines how well a solution is. | |||||
Many people have used genetic algorithms in video games to auto learn the weaknesses of players. | |||||
The beautiful part about Genetic Algorithms are their simplicity; you need absolutely no knowledge of linear algebra or calculus. | |||||
To implement a genetic algorithm from scratch you only need **very basic** algebra and a general grasp of evolution. | |||||
# Genetic Algorithm | |||||
All genetic algorithms typically have a single cycle where you continuously mutate, breed, and select the most optimal solutions. | |||||
I will dive into each section of this algorithm using simple JavaScript code snippets. | |||||
The algorithm which I present is very generic and modular so it should be easy to port into other programming languages and applications. | |||||
![Genetic Algorithms Flow Chart](media/GA/GAFlowChart.svg) | |||||
## Population Creation | |||||
The very first thing we need to do is specify a data-structure for storing our genetic information. | |||||
In biology, chromosomes are composed of sequences of genes. | |||||
Many people run genetic algorithms on binary arrays since they more closely represent DNA. | |||||
However, as computer scientists, it is often easier to model problems using continuous numbers. | |||||
In this approach, every gene will be a single floating point number ranging between zero and one. | |||||
Every type of gene will have a max and min value which represents the absolute extremes of that gene. | |||||
This works well for optimization because it allows us to easily limit our search space. | |||||
For example, we can specify that "height" gene can only vary between 0 and 90. | |||||
To get the actual value of the gene from its \[0-1] value we simple de-normalize it. | |||||
$$ | |||||
g_{real value} = (g_{high}- g_{low})g_{norm} + g_{low} | |||||
$$ | |||||
```javascript | |||||
class Gene | |||||
{ | |||||
/** | |||||
* Constructs a new Gene to store in a chromosome. | |||||
* @param min minimum value that this gene can store | |||||
* @param max value this gene can possibly be | |||||
* @param value normalized value | |||||
*/ | |||||
constructor(min, max, value) | |||||
{ | |||||
this.min = min; | |||||
this.max = max; | |||||
this.value = value; | |||||
} | |||||
/** | |||||
* De-normalizes the value of the gene | |||||
* @returns {*} | |||||
*/ | |||||
getRealValue() | |||||
{ | |||||
return (this.max - this.min) * this.value + this.min; | |||||
} | |||||
getValue() | |||||
{ | |||||
return this.value; | |||||
} | |||||
setValue(val) | |||||
{ | |||||
this.value = val; | |||||
} | |||||
makeClone() | |||||
{ | |||||
return new Gene(this.min, this.max, this.value); | |||||
} | |||||
makeRandomGene() | |||||
{ | |||||
return new Gene(this.min, this.max, Math.random()); | |||||
} | |||||
} | |||||
``` | |||||
Now that we have genes, we can create chromosomes. | |||||
Chromosomes are simply collections of genes. | |||||
Whatever language you make this in, make sure that when you create a new chromosome it | |||||
is has a [deep copy](https://en.wikipedia.org/wiki/Object_copying) of the original genetic information rather than a shallow copy. | |||||
A shallow copy is when you simple copy the object pointer where a deep copy is actually creating a new object. | |||||
If you fail to do a deep copy, you will have weird issues where multiple chromosomes will share the same DNA. | |||||
In this class I added helper functions to clone the chromosome as a random copy. | |||||
You can only create a new chromosome by cloning because I wanted to keep the program generic and make no assumptions about the domain. | |||||
Since you only provide the min/max information for the genes once, cloning an existing chromosome is the easiest way of | |||||
ensuring that all corresponding chromosomes contain genes with identical extrema. | |||||
```javascript | |||||
class Chromosome | |||||
{ | |||||
/** | |||||
* Constructs a chromosome by making a copy of | |||||
* a list of genes. | |||||
* @param geneArray | |||||
*/ | |||||
constructor(geneArray) | |||||
{ | |||||
this.genes = []; | |||||
for(let i = 0; i < geneArray.length; i++) | |||||
{ | |||||
this.genes.push(geneArray[i].makeClone()); | |||||
} | |||||
} | |||||
getGenes() | |||||
{ | |||||
return this.genes; | |||||
} | |||||
/** | |||||
* Mutates a random gene. | |||||
*/ | |||||
mutate() | |||||
{ | |||||
this.genes[Math.round(Math.random() * (this.genes.length-1))].setValue(Math.random()); | |||||
} | |||||
/** | |||||
* Creates a totally new chromosome with same | |||||
* genetic structure as this chromosome but different | |||||
* values. | |||||
* @returns {Chromosome} | |||||
*/ | |||||
createRandomChromosome() | |||||
{ | |||||
let geneAr = []; | |||||
for(let i = 0; i < this.genes.length; i++) | |||||
{ | |||||
geneAr.push(this.genes[i].makeRandomGene()); | |||||
} | |||||
return new Chromosome(geneAr); | |||||
} | |||||
} | |||||
``` | |||||
Creating a random population is pretty straight forward if implemented a method to create a random clone of a chromosome. | |||||
```javascript | |||||
/** | |||||
* Creates a totally random population based on a desired size | |||||
* and a prototypical chromosome. | |||||
* | |||||
* @param geneticChromosome | |||||
* @param populationSize | |||||
* @returns {Array} | |||||
*/ | |||||
const createRandomPopulation = function(geneticChromosome, populationSize) | |||||
{ | |||||
let population = []; | |||||
for(let i = 0; i < populationSize; i++) | |||||
{ | |||||
population.push(geneticChromosome.createRandomChromosome()); | |||||
} | |||||
return population; | |||||
}; | |||||
``` | |||||
This is where nearly all the domain information is introduced. | |||||
After you define what types of genes are found on each chromosome, you can create an entire population. | |||||
In this example all genes contain values ranging between one and ten. | |||||
```javascript | |||||
let gene1 = new Gene(1,10,10); | |||||
let gene2 = new Gene(1,10,0.4); | |||||
let geneList = [gene1, gene2]; | |||||
let exampleOrganism = new Chromosome(geneList); | |||||
let population = createRandomPopulation(genericChromosome, 100); | |||||
``` | |||||
## Evaluate Fitness | |||||
Like all optimization problems, you need a way to evaluate the performance of a particular solution. | |||||
The cost function takes in a chromosome and evaluates how close it got to the ideal solution. | |||||
This particular example it is just computing the [Manhattan Distance](https://en.wiktionary.org/wiki/Manhattan_distance) to a random 2D point. | |||||
I chose two dimensions because it is easy to graph, however, real applications may have dozens of genes on each chromosome. | |||||
```javascript | |||||
let costx = Math.random() * 10; | |||||
let costy = Math.random() * 10; | |||||
/** Defines the cost as the "distance" to a 2-d point. | |||||
* @param chromosome | |||||
* @returns {number} | |||||
*/ | |||||
const basicCostFunction = function(chromosome) | |||||
{ | |||||
return Math.abs(chromosome.getGenes()[0].getRealValue() - costx) + | |||||
Math.abs(chromosome.getGenes()[1].getRealValue() - costy); | |||||
}; | |||||
``` | |||||
## Selection | |||||
Selecting the best performing chromosomes is straightforward after you have a function for evaluating the performance. | |||||
This code snippet also computes the average and best chromosome of the population to make it easier to graph and define | |||||
the stopping point for the algorithm's main loop. | |||||
```javascript | |||||
/** | |||||
* Function which computes the fitness of everyone in the | |||||
* population and returns the most fit survivors. Method | |||||
* known as elitism. | |||||
* | |||||
* @param population | |||||
* @param keepNumber | |||||
* @param fitnessFunction | |||||
* @returns {{average: number, | |||||
* survivors: Array, bestFit: Chromosome }} | |||||
*/ | |||||
const naturalSelection = function(population, keepNumber, fitnessFunction) | |||||
{ | |||||
let fitnessArray = []; | |||||
let total = 0; | |||||
for(let i = 0; i < population.length; i++) | |||||
{ | |||||
const fitness = fitnessFunction(population[i]); | |||||
fitnessArray.push({fit:fitness, chrom: population[i]}); | |||||
total+= fitness; | |||||
} | |||||
fitnessArray.sort(predicateBy("fit")); | |||||
let survivors = []; | |||||
let bestFitness = fitnessArray[0].fit; | |||||
let bestChromosome = fitnessArray[0].chrom; | |||||
for(let i = 0; i < keepNumber; i++) | |||||
{ | |||||
survivors.push(fitnessArray[i].chrom); | |||||
} | |||||
return {average: total/population.length, survivors: survivors, bestFit: bestFitness, bestChrom: bestChromosome}; | |||||
}; | |||||
``` | |||||
You might be wondering how I sorted the list of JSON objects - not a numerical array. | |||||
I used the following function as a comparator for JavaScript's built in sort function. | |||||
This comparator will compare objects based on a specific attribute that you give it. | |||||
This is a very handy function to include in all of your JavaScript projects for easy sorting. | |||||
```javascript | |||||
/** | |||||
* Helper function to sort an array | |||||
* | |||||
* @param prop name of JSON property to sort by | |||||
* @returns {function(*, *): number} | |||||
*/ | |||||
function predicateBy(prop) | |||||
{ | |||||
return function(a,b) | |||||
{ | |||||
var result; | |||||
if(a[prop] > b[prop]) | |||||
{ | |||||
result = 1; | |||||
} | |||||
else if(a[prop] < b[prop]) | |||||
{ | |||||
result = -1; | |||||
} | |||||
return result; | |||||
} | |||||
} | |||||
``` | |||||
## Reproduction | |||||
The process of reproduction can be broken down into Pairing and Mating. | |||||
### Pairing | |||||
Pairing is the process of selecting mates to produce offspring. | |||||
A typical approach will separate the population into two segments of mothers and fathers. | |||||
You then randomly pick pairs of mothers and fathers to produce offspring. | |||||
It is ok if one chromosome mates more than once. | |||||
It is just important that you keep this process random. | |||||
```javascript | |||||
/** | |||||
* Randomly everyone in the population | |||||
* | |||||
* @param population | |||||
* @param desiredPopulationSize | |||||
*/ | |||||
const matePopulation = function(population, desiredPopulationSize) | |||||
{ | |||||
const originalLength = population.length; | |||||
while(population.length < desiredPopulationSize) | |||||
{ | |||||
let index1 = Math.round(Math.random() * (originalLength-1)); | |||||
let index2 = Math.round(Math.random() * (originalLength-1)); | |||||
if(index1 !== index2) | |||||
{ | |||||
const babies = breed(population[index1], population[index2]); | |||||
population.push(babies[0]); | |||||
population.push(babies[1]); | |||||
} | |||||
} | |||||
}; | |||||
``` | |||||
### Mating | |||||
Mating is the actual act of forming new chromosomes/organisms based on your previously selected pairs. | |||||
From my research, there are two major forms of mating: blending, crossover. | |||||
Blending is typically the most preferred approach to mating when dealing with continuous variables. | |||||
In this approach you combine the genes of both parents based on a random factor. | |||||
$$ | |||||
c_{new} = r * c_{mother} + (1-r) * c_{father} | |||||
$$ | |||||
The second offspring simply uses (1-r) for their random factor to adjust the chromosomes. | |||||
Crossover is the simplest approach to mating. | |||||
In this process you clone the parents and then you randomly swap *n* of their genes. | |||||
This works fine in some scenarios; however, this severely lacks the genetic diversity of the genes because you now have to solely | |||||
rely on mutations for changes. | |||||
```javascript | |||||
/** | |||||
* Mates two chromosomes using the blending method | |||||
* and returns a list of 2 offspring. | |||||
* @param father | |||||
* @param mother | |||||
* @returns {Chromosome[]} | |||||
*/ | |||||
const breed = function(father, mother) | |||||
{ | |||||
let son = new Chromosome(father.getGenes()); | |||||
let daughter = new Chromosome(mother.getGenes()); | |||||
for(let i = 0;i < son.getGenes().length; i++) | |||||
{ | |||||
let blendCoef = Math.random(); | |||||
blendGene(son.getGenes()[i], daughter.getGenes()[i], blendCoef); | |||||
} | |||||
return [son, daughter]; | |||||
}; | |||||
/** | |||||
* Blends two genes together based on a random blend | |||||
* coefficient. | |||||
**/ | |||||
const blendGene = function(gene1, gene2, blendCoef) | |||||
{ | |||||
let value1 = (blendCoef * gene1.getValue()) + | |||||
(gene2.getValue() * (1- blendCoef)); | |||||
let value2 = ((1-blendCoef) * gene1.getValue()) + | |||||
(gene2.getValue() * blendCoef); | |||||
gene1.setValue(value1); | |||||
gene2.setValue(value2); | |||||
}; | |||||
``` | |||||
## Mutation | |||||
Mutations are random changes to an organisms DNA. | |||||
In the scope of genetic algorithms, it helps our population converge on the correct solution. | |||||
You can either adjust genes by a factor resulting in a smaller change or, you can | |||||
change the value of the gene to be something completely random. | |||||
Since we are using the blending technique for reproduction, we already have small incremental changes. | |||||
I prefer to use mutations to randomly change the entire gene since it helps prevent the algorithm | |||||
from settling on a local minimum rather than the global minimum. | |||||
```javascript | |||||
/** | |||||
* Randomly mutates the population | |||||
**/ | |||||
const mutatePopulation = function(population, mutatePercentage) | |||||
{ | |||||
if(population.length >= 2) | |||||
{ | |||||
let mutations = mutatePercentage * | |||||
population.length * | |||||
population[0].getGenes().length; | |||||
for(let i = 0; i < mutations; i++) | |||||
{ | |||||
population[i].mutate(); | |||||
} | |||||
} | |||||
else | |||||
{ | |||||
console.log("Error, population too small to mutate"); | |||||
} | |||||
}; | |||||
``` | |||||
## Immigration | |||||
Immigration or "new blood" is the process of dumping random organisms into your population at each generation. | |||||
This prevents us from getting stuck in a local minimum rather than the global minimum. | |||||
There are more advanced techniques to accomplish this same concept. | |||||
My favorite approach (not implemented here) is raising **x** populations simultaneously and every **y** generations | |||||
you take **z** organisms from each population and move them to another population. | |||||
```javascript | |||||
/** | |||||
* Introduces x random chromosomes to the population. | |||||
* @param population | |||||
* @param immigrationSize | |||||
*/ | |||||
const newBlood = function(population, immigrationSize) | |||||
{ | |||||
for(let i = 0; i < immigrationSize; i++) | |||||
{ | |||||
let geneticChromosome = population[0]; | |||||
population.push(geneticChromosome.createRandomChromosome()); | |||||
} | |||||
}; | |||||
``` | |||||
## Putting It All Together | |||||
Now that we have all the ingredients for a genetic algorithm we can piece it together in a simple loop. | |||||
```javascript | |||||
/** | |||||
* Runs the genetic algorithm by going through the processes of | |||||
* natural selection, mutation, mating, and immigrations. This | |||||
* process will continue until an adequately performing chromosome | |||||
* is found or a generation threshold is passed. | |||||
* | |||||
* @param geneticChromosome Prototypical chromosome: used so algo knows | |||||
* what the dna of the population looks like. | |||||
* @param costFunction Function which defines how bad a Chromosome is | |||||
* @param populationSize Desired population size for population | |||||
* @param maxGenerations Cut off level for number of generations to run | |||||
* @param desiredCost Sufficient cost to terminate program at | |||||
* @param mutationRate Number between [0,1] representing proportion of genes | |||||
* to mutate each generation | |||||
* @param keepNumber Number of Organisms which survive each generation | |||||
* @param newBloodNumber Number of random immigrants to introduce into | |||||
* the population each generation. | |||||
* @returns {*} | |||||
*/ | |||||
const runGeneticOptimization = function(geneticChromosome, costFunction, | |||||
populationSize, maxGenerations, | |||||
desiredCost, mutationRate, keepNumber, | |||||
newBloodNumber) | |||||
{ | |||||
let population = createRandomPopulation(geneticChromosome, populationSize); | |||||
let generation = 0; | |||||
let bestCost = Number.MAX_VALUE; | |||||
let bestChromosome = geneticChromosome; | |||||
do | |||||
{ | |||||
matePopulation(population, populationSize); | |||||
newBlood(population, newBloodNumber); | |||||
mutatePopulation(population, mutationRate); | |||||
let generationResult = naturalSelection(population, keepNumber, costFunction); | |||||
if(bestCost > generationResult.bestFit) | |||||
{ | |||||
bestChromosome = generationResult.bestChrom; | |||||
bestCost = generationResult.bestFit; | |||||
} | |||||
population = generationResult.survivors; | |||||
generation++; | |||||
console.log("Generation " + generation + " Best Cost: " + bestCost); | |||||
}while(generation < maxGenerations && bestCost > desiredCost); | |||||
return bestChromosome; | |||||
}; | |||||
``` | |||||
## Running | |||||
Running the program is pretty straight forward after you have your genes and cost function defined. | |||||
You might be wondering if there is an optimal configuration of parameters to use with this algorithm. | |||||
The answer is that it varies based on the particular problem. | |||||
Problems like the one graphed by this website perform very well with a low mutation rate and a high population. | |||||
However, some higher dimensional problems won't even converge on a local answer if you set your mutation rate too low. | |||||
```javascript | |||||
let gene1 = new Gene(1,10,10); | |||||
... | |||||
let geneN = new Gene(1,10,0.4); | |||||
let geneList = [gene1,..., geneN]; | |||||
let exampleOrganism = new Chromosome(geneList); | |||||
costFunction = function(chromosome) | |||||
{ | |||||
var d =...; | |||||
//compute cost | |||||
return d; | |||||
} | |||||
runGeneticOptimization(exampleOrganism, costFunction, 100, 50, 0.01, 0.3, 20, 10); | |||||
``` | |||||
The complete code for the genetic algorithm and the fancy JavaScript graphs can be found in my [Random Scripts GitHub Repository](https://github.com/jrtechs/RandomScripts). | |||||
In the future I may package this into an [npm](https://www.npmjs.com/) package. |
@ -0,0 +1,72 @@ | |||||
Shortly after working on my [Steam Friends Graph](https://jrtechs.net/projects/steam-friends-graph) | |||||
,I had the idea of extending the project to include the GitHub network. | |||||
I used [BrickHack V](https://brickhack.io/) as the opportunity to work on this project with my friends. | |||||
Rather than simply use the code that was used in the Steam friends graph, the architecture was completely | |||||
revamped to reflect both the differences between the Steam and GitHub networks and my improved web development skills. | |||||
# Project Overview | |||||
We created an interactive website which allows you to make graphs based on the Github network. | |||||
Currently the site generates three types of graphs-- the most popular and entertaining of which is the friends graph. | |||||
The friends graph helps you visualize clusters of friends/collaborators on GitHub. | |||||
Similar to the Steam Friends Project, I hope that this project will make people more interested in learning about big data. | |||||
The visual aspect of this website makes learning about topics such as clustering and graph databases more intuitive. | |||||
## Friends View | |||||
![Friends Graph of JrTechs](media/github/jrtechsGraph.png) | |||||
The friends view displays all of the people which you following and your followers. | |||||
This also connects connects everyone in the graph which are following each other. | |||||
## Repository View | |||||
![Repositories Timeline for JrTechs](media/github/RepositoriesView.png) | |||||
## Organization View | |||||
![Organization view for RITlug](media/github/ritlugOrg.png) | |||||
![Organization view for FOSS@MAGIC](media/github/fossRITOrg.png) | |||||
## Technologies Used | |||||
- [BootStrap](https://getbootstrap.com/) | |||||
- [jQuery](https://jquery.com/) | |||||
- [Vis JS](http://visjs.org/) | |||||
- [Github v3 API](https://developer.github.com/v3/) | |||||
- [Node.js](https://nodejs.org/en/) | |||||
# Changes From the Steam Graph Project | |||||
The one stark difference between the Steam network and GitHub is the amount of friends that people have. | |||||
Most developers on GitHub typically only follows around 20 people where it is not uncommon for people on Steam to have well over 100 friends. | |||||
Due to the smaller graphs, I was able to use VisJS which has nicer animations and supports custom HTML for each node. | |||||
![Jrtechs Steam Friends Network](media/steam/jrtechs1.png) | |||||
Another big change to the architecture was the way in which graphs are sent to the client. | |||||
The server generated the graph and then sent the nodes and edges to the client over a web socket for the steam graph. | |||||
In this project, the client builds the graph and queries the server using ajax for the necessary information. | |||||
This gives the client a more dynamic loading progress and makes hosting the application much easier. | |||||
# Future Work | |||||
Since this project was initially created during a hackathon, there is a **lot** of work to be done. | |||||
I will outline a few ideas which I have. | |||||
- Improved Caching and Performance | |||||
- Friends of Friends -- similar to Steam's graph | |||||
- Graphs Linking Users and Repositories Based on Activity | |||||
- Code Metrics | |||||
# Contributing | |||||
If you want to contribute to this project and don't know where to start, look at the open issues on [GitHub](https://github.com/jrtechs/github-graphs). | |||||
Once you know what you want to work on, just discuss it in the issues and file a pull request. | |||||
I are very open to new contributes. | |||||
<youtube src="rz7KD_d-uQg" /> |