Add basic string genetic algorithm

Author: D4rkia

genetic-algorithm/genetic_algo.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"math/rand"
+	"os"
+	"sort"
+	"strconv"
+	"time"
+	"unicode/utf8"
+)
+
+type populationItem struct {
+	Key   string
+	Value float64
+}
+
+func main() {
+	// Define a random seed
+	rand.Seed(time.Now().UnixNano())
+
+	// Define parameters
+	sentence := string("This is a genetic algorithm to evaluate, combine, evolve  mutate a string!")
+	charmap := []rune(" ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz.,;!?+-*#@^'èéòà€ù=)(&%$£/\\")
+	populationNum := 200
+	selectionNum := 50
+	mutationProb := .1
+
+	// Verify the presence of all char in sentence
+	for position, r := range []rune(sentence) {
+		find := func() bool {
+			for _, n := range charmap {
+				if n == r {
+					return true
+				}
+			}
+			return false
+		}
+		if !find() {
+			fmt.Println(errors.New("Character not aviable in charmap"), position, "\"", string(r), "\"")
+			os.Exit(1)
+		}
+	}
+
+	// Generate random population
+	pop := make([]populationItem, populationNum, populationNum)
+	for i := 0; i < populationNum; i++ {
+		key := ""
+		for x := 0; x < utf8.RuneCountInString(sentence); x++ {
+			choice := rand.Intn(len(charmap))
+			key += string(charmap[choice])
+		}
+		pop[i] = populationItem{key, 0}
+	}
+
+	for gen, generatedPop := 1, 0; ; gen++ {
+		generatedPop += len(pop)
+
+		// Random population created now it's time to evaluate
+		for i, item := range pop {
+			itemKey, sentenceRune := []rune(item.Key), []rune(sentence)
+			for x := 0; x < len(sentence); x++ {
+				if itemKey[x] == sentenceRune[x] {
+					pop[i].Value++
+				}
+			}
+			pop[i].Value = pop[i].Value / float64(len(sentenceRune))
+		}
+		// Check if there is a right evolution
+		sort.SliceStable(pop, func(i, j int) bool { return pop[i].Value > pop[j].Value })
+		if pop[0].Key == sentence {
+			fmt.Println("Generation:", strconv.Itoa(gen), "Analyzed:", generatedPop, "Best:", pop[0])
+			break
+		}
+		// Print the best result
+		if gen%1000 == 0 {
+			fmt.Println("Generation:", strconv.Itoa(gen), "Analyzed:", generatedPop, "Best:", pop[0])
+		}
+		// Combine, Evolve and Mutate
+		var popChildren []populationItem
+		for i := 0; i < int(selectionNum); i++ {
+			parent1 := pop[i]
+			parent2 := pop[i+1]
+			split := rand.Intn(utf8.RuneCountInString(sentence))
+
+			// Save Children 1
+			child := append([]rune(parent1.Key)[:split], []rune(parent2.Key)[split:]...)
+			if rand.Float64() > mutationProb {
+				child[rand.Intn(len(child))] = charmap[rand.Intn(len(charmap))]
+			}
+			popChildren = append(popChildren, populationItem{string(child), 0})
+
+			// Save Children 2
+			child = append([]rune(parent2.Key)[:split], []rune(parent1.Key)[split:]...)
+			if rand.Float64() > mutationProb {
+				child[rand.Intn(len(child))] = charmap[rand.Intn(len(charmap))]
+			}
+			popChildren = append(popChildren, populationItem{string(child), 0})
+		}
+		pop = popChildren
+	}
+}