From 1403cdc8d86af066d1097c7489ea9f9acd77fe8f Mon Sep 17 00:00:00 2001
From: Frederic Langlet <flanglet@gmail.com>
Date: Fri, 26 Jan 2024 11:46:17 -0800
Subject: [PATCH] Make benchmarks more consistent across invocations

---
 v2/benchmark/BWT_test.go        | 6 +++---
 v2/benchmark/Entropy_test.go    | 4 +++-
 v2/benchmark/Transforms_test.go | 4 +++-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/v2/benchmark/BWT_test.go b/v2/benchmark/BWT_test.go
index bfa66eca..ce057343 100644
--- a/v2/benchmark/BWT_test.go
+++ b/v2/benchmark/BWT_test.go
@@ -20,7 +20,6 @@ import (
 	"fmt"
 	"math/rand"
 	"testing"
-	"time"
 
 	kanzi "github.com/flanglet/kanzi-go/v2"
 	"github.com/flanglet/kanzi-go/v2/transform"
@@ -50,8 +49,9 @@ func testBWTSpeed(isBWT bool, iter, size int) error {
 	buf3 := make([]byte, size)
 
 	for jj := 0; jj < 3; jj++ {
+		// Initialize with a fixed seed to get consistent results
+		r := rand.New(rand.NewSource(int64(jj * 1234567)))
 		var bwt kanzi.ByteTransform
-		rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
 
 		for i := 0; i < iter; i++ {
 			if isBWT {
@@ -61,7 +61,7 @@ func testBWTSpeed(isBWT bool, iter, size int) error {
 			}
 
 			for i := range buf1 {
-				buf1[i] = byte(rnd.Intn(255) + 1)
+				buf1[i] = byte(r.Intn(255) + 1)
 			}
 
 			_, _, err1 := bwt.Forward(buf1, buf2)
diff --git a/v2/benchmark/Entropy_test.go b/v2/benchmark/Entropy_test.go
index f22d2b77..407bf30c 100644
--- a/v2/benchmark/Entropy_test.go
+++ b/v2/benchmark/Entropy_test.go
@@ -105,6 +105,8 @@ func getDecoder(name string, ibs kanzi.InputBitStream) kanzi.EntropyDecoder {
 }
 
 func testEntropySpeed(b *testing.B, name string) error {
+	// Initialize with a fixed seed to get consistent results
+	r := rand.New(rand.NewSource(1234567))
 	repeats := []int{3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9, 3}
 
 	for jj := 0; jj < 3; jj++ {
@@ -122,7 +124,7 @@ func testEntropySpeed(b *testing.B, name string) error {
 
 				length := repeats[idx]
 				idx = (idx + 1) & 0x0F
-				b := byte(rand.Intn(256))
+				b := byte(r.Intn(256))
 
 				if i0+length >= size {
 					length = size - i0 - 1
diff --git a/v2/benchmark/Transforms_test.go b/v2/benchmark/Transforms_test.go
index 5243c133..f83d803b 100644
--- a/v2/benchmark/Transforms_test.go
+++ b/v2/benchmark/Transforms_test.go
@@ -153,6 +153,8 @@ func BenchmarkMTFT(b *testing.B) {
 }
 
 func testTransformSpeed(name string, iter int) error {
+	// Initialize with a fixed seed to get consistent results
+	r := rand.New(rand.NewSource(1234567))
 	size := 50000
 
 	for jj := 0; jj < 3; jj++ {
@@ -165,7 +167,7 @@ func testTransformSpeed(name string, iter int) error {
 		n := iter / 20
 
 		for n < len(input) {
-			val := byte(rand.Intn(64))
+			val := byte(r.Intn(64))
 
 			if val%7 == 0 {
 				val = 0