Creating a Random Choice with weight in Golang

randomChoice.go

package main

import (
  "fmt"
  "math/rand"
  "sync"
  "time"
)

func main() {
  rand.Seed(time.Now().Unix()) // Seeding for pseudo random
  
  cat1 := []string{"Hello", "World"}
  wt1 := []float32{0.9,0.1}

  result := randomChoice(1 << 23, cat1, wt1) //Creating array with len 2^23

  countString(cat1, result)

}

func randomChoice(size int, choice []string, weight []float32) []string{
  // max number can varies, higher number will yield better result but longer computation time
  // i find 2^8 is quite satisfying
  var wg sync.WaitGroup
  max := 1 << 8 
  
  // Creating a pool which we later draw upon
  pp:= make([]string, max)
  weightSize := make([]int, len(weight))

  for i := 0; i < len(weight); i++ {
    weightSize[i] = int(weight[i] * float32(max)) + 1
  }

  wg.Add(max)
  categoryAppend := 0

  go func() {
    for i := 0; i < max; i++ {
      pp[i] = choice[categoryAppend]
      weightSize[categoryAppend]--
      wg.Done()
      if weightSize[categoryAppend] == 0 {
        categoryAppend++
      }
    }
  }()
  wg.Wait()
  
  // drawing from the pool we just makes
  result := make([]string, size)
  for i := 0; i < size; i++ {
    result[i] = pp[rand.Intn(max)]
  }
  return result
}

func countString(choice []string, array []string) {
  var wg sync.WaitGroup

  countCat := make(map[string]int)
  for _,v := range choice {
    countCat[v] = 0
  }

  wg.Add(len(array))
  go func() {
    for i := 0; i < len(array); i++ {
      for _, v := range choice {
        if v == array[i]{
          countCat[v]++
        }
      }
      wg.Done()
    }
  }()
  wg.Wait()
  
  // verifying our random generated choice based on weight
  for k, v := range countCat {
    fmt.Println(k, "::", v, ":: RATIO", float32(v)/float32(len(array)))
  }
}