mirror of
https://github.com/golang/go
synced 2024-11-24 16:00:12 -07:00
122 lines
3.3 KiB
Go
122 lines
3.3 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"math/rand"
|
|
)
|
|
|
|
const (
|
|
win = 100 // The winning score in a game of Pig
|
|
gamesPerSeries = 10 // The number of games per series to simulate
|
|
)
|
|
|
|
// A score includes scores accumulated in previous turns for each player,
|
|
// as well as the points scored by the current player in this turn.
|
|
type score struct {
|
|
player, opponent, thisTurn int
|
|
}
|
|
|
|
// An action transitions stochastically to a resulting score.
|
|
type action func(current score) (result score, turnIsOver bool)
|
|
|
|
// roll returns the (result, turnIsOver) outcome of simulating a die roll.
|
|
// If the roll value is 1, then thisTurn score is abandoned, and the players'
|
|
// roles swap. Otherwise, the roll value is added to thisTurn.
|
|
func roll(s score) (score, bool) {
|
|
outcome := rand.Intn(6) + 1 // A random int in [1, 6]
|
|
if outcome == 1 {
|
|
return score{s.opponent, s.player, 0}, true
|
|
}
|
|
return score{s.player, s.opponent, outcome + s.thisTurn}, false
|
|
}
|
|
|
|
// stay returns the (result, turnIsOver) outcome of staying.
|
|
// thisTurn score is added to the player's score, and the players' roles swap.
|
|
func stay(s score) (score, bool) {
|
|
return score{s.opponent, s.player + s.thisTurn, 0}, true
|
|
}
|
|
|
|
// A strategy chooses an action for any given score.
|
|
type strategy func(score) action
|
|
|
|
// stayAtK returns a strategy that rolls until thisTurn is at least k, then stays.
|
|
func stayAtK(k int) strategy {
|
|
return func(s score) action {
|
|
if s.thisTurn >= k {
|
|
return stay
|
|
}
|
|
return roll
|
|
}
|
|
}
|
|
|
|
// play simulates a Pig game and returns the winner (0 or 1).
|
|
func play(strategy0, strategy1 strategy) int {
|
|
strategies := []strategy{strategy0, strategy1}
|
|
var s score
|
|
var turnIsOver bool
|
|
currentPlayer := rand.Intn(2) // Randomly decide who plays first
|
|
for s.player+s.thisTurn < win {
|
|
action := strategies[currentPlayer](s)
|
|
s, turnIsOver = action(s)
|
|
if turnIsOver {
|
|
currentPlayer = (currentPlayer + 1) % 2
|
|
}
|
|
}
|
|
return currentPlayer
|
|
}
|
|
|
|
// roundRobin simulates a series of games between every pair of strategies.
|
|
func roundRobin(strategies []strategy) ([]int, int) {
|
|
wins := make([]int, len(strategies))
|
|
for i := 0; i < len(strategies); i++ {
|
|
for j := i + 1; j < len(strategies); j++ {
|
|
for k := 0; k < gamesPerSeries; k++ {
|
|
winner := play(strategies[i], strategies[j])
|
|
if winner == 0 {
|
|
wins[i]++
|
|
} else {
|
|
wins[j]++
|
|
}
|
|
}
|
|
}
|
|
}
|
|
gamesPerStrategy := gamesPerSeries * (len(strategies) - 1) // no self play
|
|
return wins, gamesPerStrategy
|
|
}
|
|
|
|
// ratioString takes a list of integer values and returns a string that lists
|
|
// each value and its percentage of the sum of all values.
|
|
// e.g., ratios(1, 2, 3) = "1/6 (16.7%), 2/6 (33.3%), 3/6 (50.0%)"
|
|
func ratioString(vals ...int) string {
|
|
total := 0
|
|
for _, val := range vals {
|
|
total += val
|
|
}
|
|
s := ""
|
|
for _, val := range vals {
|
|
if s != "" {
|
|
s += ", "
|
|
}
|
|
pct := 100 * float64(val) / float64(total)
|
|
s += fmt.Sprintf("%d/%d (%0.1f%%)", val, total, pct)
|
|
}
|
|
return s
|
|
}
|
|
|
|
func main() {
|
|
strategies := make([]strategy, win)
|
|
for k := range strategies {
|
|
strategies[k] = stayAtK(k + 1)
|
|
}
|
|
wins, games := roundRobin(strategies)
|
|
|
|
for k := range strategies {
|
|
fmt.Printf("Wins, losses staying at k =% 4d: %s\n",
|
|
k+1, ratioString(wins[k], games-wins[k]))
|
|
}
|
|
}
|