From 30f94d6eae4e10ad012741511b4bbf7cf308b8b7 Mon Sep 17 00:00:00 2001
From: "kayos@tcp.direct" <kayos@tcp.direct>
Date: Tue, 12 Jul 2022 02:00:54 -0700
Subject: [PATCH] Enhancement: shared/global rand objs + add benchmarks

---
 entropy/entropy.go      | 30 +++++++++++++++++++++------
 entropy/entropy_test.go | 46 +++++++++++++++++++++++++++++++++++++----
 2 files changed, 66 insertions(+), 10 deletions(-)

diff --git a/entropy/entropy.go b/entropy/entropy.go
index fe45954..b188d16 100644
--- a/entropy/entropy.go
+++ b/entropy/entropy.go
@@ -4,11 +4,17 @@ import (
 	crip "crypto/rand"
 	"encoding/binary"
 	"math/rand"
+	"sync"
 	"time"
 
 	"nullprogram.com/x/rng"
 )
 
+var (
+	sharedRand    *rand.Rand
+	getSharedRand = &sync.Once{}
+)
+
 // RandomStrChoice returns a random item from an input slice of strings.
 func RandomStrChoice(choice []string) string {
 	if len(choice) > 0 {
@@ -25,7 +31,8 @@ func GetCryptoSeed() int64 {
 	return seed
 }
 
-// GetOptimizedRand returns a pointer to a new rand.Rand which uses crypto/rand to seed a splitmix64 rng.
+// GetOptimizedRand returns a pointer to a *new* rand.Rand which uses crypto/rand to seed a splitmix64 rng.
+// Does not use the global/shared instance of a splitmix64 rng, but instead creates a new one.
 func GetOptimizedRand() *rand.Rand {
 	r := new(rng.SplitMix64)
 	r.Seed(GetCryptoSeed())
@@ -34,14 +41,25 @@ func GetOptimizedRand() *rand.Rand {
 
 // RNGUint32 returns a random uint32 using crypto/rand and splitmix64.
 func RNGUint32() uint32 {
-	r := GetOptimizedRand()
-	return r.Uint32()
+	getSharedRand.Do(func() {
+		sharedRand = GetOptimizedRand()
+	})
+	return sharedRand.Uint32()
 }
 
-// RNG returns integer with a maximum amount of 'n' using crypto/rand and splitmix64.
+/*RNG returns integer with a maximum amount of 'n' using a global/shared instance of a splitmix64 rng.
+  - Benchmark_FastRandStr5-24            25205089      47.03 ns/op
+  - Benchmark_FastRandStr25-24       	7113620     169.8  ns/op
+  - Benchmark_FastRandStr55-24       	3520297     340.7  ns/op
+  - Benchmark_FastRandStr500-24      	 414966    2837    ns/op
+  - Benchmark_FastRandStr55555-24    	   3717  315229    ns/op
+
+*/
 func RNG(n int) int {
-	r := GetOptimizedRand()
-	return r.Intn(n)
+	getSharedRand.Do(func() {
+		sharedRand = GetOptimizedRand()
+	})
+	return sharedRand.Intn(n)
 }
 
 // OneInA generates a random number with a maximum of 'million' (input int).
diff --git a/entropy/entropy_test.go b/entropy/entropy_test.go
index f3e0372..240bf8d 100644
--- a/entropy/entropy_test.go
+++ b/entropy/entropy_test.go
@@ -2,6 +2,7 @@ package entropy
 
 import (
 	"strings"
+	"sync"
 	"testing"
 )
 
@@ -41,10 +42,10 @@ func Test_RandStr(t *testing.T) {
 	for n := 0; n != 500; n++ {
 		zero := RandStr(55)
 		one := RandStr(55)
-		t.Logf("Random0: %s Random1: %s", zero, one)
+		// t.Logf("Random0: %s Random1: %s", zero, one)
 		randStrChecks(zero, one, t)
 	}
-
+	t.Logf("[SUCCESS] RandStr had no collisions")
 }
 
 func Test_RandStr_Entropy(t *testing.T) {
@@ -67,10 +68,10 @@ func Test_RandStr_Entropy(t *testing.T) {
 			t.Errorf("[ENTROPY FAILURE] more than a quarter of the string is the same!\n zero: %s \n one: %s \nTotal similar: %d",
 				zero, one, similarity)
 		}
-		t.Logf("[ENTROPY] Similarity score (lower is better): %d", similarity)
+		// t.Logf("[ENTROPY] Similarity score (lower is better): %d", similarity)
 		totalScore += similarity
 	}
-	t.Logf("[ENTROPY] final score (lower is better): %d", totalScore)
+	t.Logf("[ENTROPY] final score (lower is better): %d (RandStr)", totalScore)
 }
 
 func Test_RandomStrChoice(t *testing.T) {
@@ -83,3 +84,40 @@ func Test_RandomStrChoice(t *testing.T) {
 	}
 	check(RandomStrChoice(slice), RandomStrChoice(slice), t)
 }
+
+func Test_RNGUint32(t *testing.T) {
+	// start globals fresh, just for coverage.
+	sharedRand = GetOptimizedRand()
+	getSharedRand = &sync.Once{}
+	RNGUint32()
+}
+
+func Benchmark_RandStr5(b *testing.B) {
+	for n := 0; n != b.N; n++ {
+		RandStr(5)
+	}
+}
+
+func Benchmark_RandStr25(b *testing.B) {
+	for n := 0; n != b.N; n++ {
+		RandStr(25)
+	}
+}
+
+func Benchmark_RandStr55(b *testing.B) {
+	for n := 0; n != b.N; n++ {
+		RandStr(55)
+	}
+}
+
+func Benchmark_RandStr500(b *testing.B) {
+	for n := 0; n != b.N; n++ {
+		RandStr(500)
+	}
+}
+
+func Benchmark_RandStr55555(b *testing.B) {
+	for n := 0; n != b.N; n++ {
+		RandStr(55555)
+	}
+}