add epislion greedy

algo/epsilon_greedy.go

@@ -0,0 +1,39 @@
+package algo
+
+import (
+	"lukechampine.com/frand"
+	"tuxpa.in/a/gambit/helper"
+)
+
+type EpsilonGreedy struct {
+	Epsilon float64
+	cr      helper.CountReward
+}
+
+func (u *EpsilonGreedy) Select(r float64) int {
+	if r > u.Epsilon {
+		return int(u.cr.RewardMax())
+	}
+	return frand.Intn(u.cr.Size())
+}
+
+func (u *EpsilonGreedy) Update(a int, r float64) error {
+	return u.cr.Update(a, r)
+}
+
+func (u *EpsilonGreedy) Reset(n int) error {
+	u.cr.ResetTo(n)
+	return nil
+}
+
+func (u *EpsilonGreedy) Size() int {
+	return u.cr.Size()
+}
+
+func (u *EpsilonGreedy) Count(res []int) {
+	u.cr.Count(res)
+}
+
+func (u *EpsilonGreedy) Reward(res []float64) {
+	u.cr.Reward(res)
+}

algo/mutex.go

@@ -40,3 +40,9 @@ func (s *Sync) Reward(res *[]float64) {
 	defer s.mu.Unlock()
 	s.Reward(res)
 }
+
+func (s *Sync) Size() int {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.Size()
+}

algo/ucb.go

@@ -1,7 +1,6 @@
-package algo
+package ucb
 
 import (
-	"errors"
 	"math"
 
 	"tuxpa.in/a/gambit/helper"
@@ -30,15 +29,8 @@ func (ucb *UCB) Select(r float64) int {
 }
 
 func (u *UCB) Update(a int, r float64) error {
-	if a < 0 || a >= len(u.cr.Rewards) || r < 0 {
-		return errors.New("TODO")
+	return u.cr.Update(a, r)
 }
-	u.cr.Counts[a]++
-	dec := float64(u.cr.Counts[a])
-	u.cr.Rewards[a] = (u.cr.Rewards[a]*(dec-1) + r) / dec
-	return nil
-}
-
 func (u *UCB) Reset(n int) error {
 	u.cr.ResetTo(n)
 	return nil

gambit.go

@@ -5,6 +5,8 @@ type Bandit interface {
 	Update(a int, r float64) error
 	Reset(n int) error
 
-	Count(res *[]int)
-	Reward(res *[]float64)
+	Size() int
+
+	Count(res []int)
+	Reward(res []float64)
 }

go.mod

@@ -1,3 +1,11 @@
 module tuxpa.in/a/gambit
 
 go 1.19
+
+require golang.org/x/exp v0.0.0-20230626212559-97b1e661b5df
+
+require (
+	github.com/aead/chacha20 v0.0.0-20180709150244-8b13a72661da // indirect
+	golang.org/x/sys v0.1.0 // indirect
+	lukechampine.com/frand v1.4.2 // indirect
+)

go.sum

@@ -0,0 +1,9 @@
+github.com/aead/chacha20 v0.0.0-20180709150244-8b13a72661da h1:KjTM2ks9d14ZYCvmHS9iAKVt9AyzRSqNU1qabPih5BY=
+github.com/aead/chacha20 v0.0.0-20180709150244-8b13a72661da/go.mod h1:eHEWzANqSiWQsof+nXEI9bUVUyV6F53Fp89EuCh2EAA=
+golang.org/x/exp v0.0.0-20230626212559-97b1e661b5df h1:UA2aFVmmsIlefxMk29Dp2juaUSth8Pyn3Tq5Y5mJGME=
+golang.org/x/exp v0.0.0-20230626212559-97b1e661b5df/go.mod h1:FXUEEKJgO7OQYeo8N01OfiKP8RXMtf6e8aTskBGqWdc=
+golang.org/x/sys v0.0.0-20190626221950-04f50cda93cb/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.1.0 h1:kunALQeHf1/185U1i0GOB/fy1IPRDDpuoOOqRReG57U=
+golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+lukechampine.com/frand v1.4.2 h1:RzFIpOvkMXuPMBb9maa4ND4wjBn71E1Jpf8BzJHMaVw=
+lukechampine.com/frand v1.4.2/go.mod h1:4S/TM2ZgrKejMcKMbeLjISpJMO+/eZ1zu3vYX9dtj3s=

helper/storage.go

@@ -1,5 +1,12 @@
 package helper
 
+import (
+	"errors"
+	"math"
+
+	"golang.org/x/exp/constraints"
+)
+
 type CountReward struct {
 	Counts  []int
 	Rewards []float64
@@ -22,42 +29,62 @@ func (c *CountReward) ResetTo(size int) {
 		c.Rewards[idx] = 0
 	}
 }
-
-func (c *CountReward) Count(res *[]int) {
-	if res == nil {
-		r := make([]int, len(c.Counts))
-		res = &r
+func (c *CountReward) CountMax() (i int) {
+	xs := c.Counts
+	i = math.MinInt
+	for _, v := range xs {
+		if v > i {
+			i = v
 		}
-	if len(c.Counts) < len(*res) {
-		*res = append(*res, len(c.Counts)-len(*res))
+	}
+	return
+}
+func (c *CountReward) RewardMax() (i float64) {
+	xs := c.Rewards
+	i = math.Inf(-1)
+	for _, v := range xs {
+		if v > i {
+			i = v
+		}
+	}
+	return
 }
 
-	(*res) = (*res)[:len(c.Counts)]
-
-	copy(*res, c.Counts)
+func (c *CountReward) Update(a int, r float64) error {
+	if a < 0 || a >= c.Size() || r < 0 {
+		return errors.New("TODO")
+	}
+	c.Counts[a]++
+	dec := float64(c.Counts[a])
+	c.Rewards[a] = (c.Rewards[a]*(dec-1) + r) / dec
+	return nil
 }
-
 func (c *CountReward) CountSum() (i int) {
-	for _, v := range c.Counts {
-		i = i + v
+	return sum(c.Counts)
 }
-	return i
-}
-func (c *CountReward) CountReward() (i int) {
-	for _, v := range c.Counts {
-		i = i + v
-	}
-	return i
+func (c *CountReward) RewardSum() (i float64) {
+	return sum(c.Rewards)
 }
 
-func (c *CountReward) Reward(res *[]float64) {
-	if res == nil {
-		r := make([]float64, len(c.Rewards))
-		res = &r
+func (c *CountReward) Size() int {
+	return len(c.Counts)
 }
-	if len(c.Rewards) < len(*res) {
-		*res = append(*res, make([]float64, len(c.Rewards)-len(*res))...)
+
+func (c *CountReward) Count(res []int) {
+	copy(res, c.Counts)
 }
-	(*res) = (*res)[:len(c.Rewards)]
-	copy(*res, c.Rewards)
+
+func (c *CountReward) Reward(res []float64) {
+	copy(res, c.Rewards)
+}
+
+func sum[T Numeric](n []T) (i T) {
+	for _, v := range n {
+		i = i + v
+	}
+	return
+}
+
+type Numeric interface {
+	constraints.Integer | constraints.Float
 }