add subset algorithm

core/mathx/entropy.go

@@ -2,9 +2,14 @@ package mathx
 
 import "math"
 
-func CalcEntropy(m map[interface{}]int, total int) float64 {
+func CalcEntropy(m map[interface{}]int) float64 {
 	var entropy float64
 
+	var total int
+	for _, v := range m {
+		total += v
+	}
+
 	for _, v := range m {
 		proba := float64(v) / float64(total)
 		entropy -= proba * math.Log2(proba)

core/mathx/entropy_test.go

@@ -13,5 +13,5 @@ func TestCalcEntropy(t *testing.T) {
 	for i := 0; i < total; i++ {
 		m[i] = count
 	}
-	assert.True(t, CalcEntropy(m, total*count) > .99)
+	assert.True(t, CalcEntropy(m) > .99)
 }

core/mathx/unstable_test.go

@@ -65,7 +65,7 @@ func TestUnstable_Distribution(t *testing.T) {
 	for k, v := range m {
 		mi[k] = v
 	}
-	entropy := CalcEntropy(mi, total)
+	entropy := CalcEntropy(mi)
 	assert.True(t, len(m) > 1)
 	assert.True(t, entropy > 0.95)
 }