Update to gobook@c6d7a22edd03e7738c38d5baa2174ff325d8d863

ch8/cake/cake_test.go

@@ -0,0 +1,74 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+package cake_test
+
+import (
+	"testing"
+	"time"
+
+	"gopl.io/ch8/cake"
+)
+
+var defaults = cake.Shop{
+	Verbose:      testing.Verbose(),
+	Cakes:        20,
+	BakeTime:     10 * time.Millisecond,
+	NumIcers:     1,
+	IceTime:      10 * time.Millisecond,
+	InscribeTime: 10 * time.Millisecond,
+}
+
+func Benchmark(b *testing.B) {
+	// Baseline: one baker, one icer, one inscriber.
+	// Each step takes exactly 10ms.  No buffers.
+	cakeshop := defaults
+	cakeshop.Work(b.N) // 224 ms
+}
+
+func BenchmarkBuffers(b *testing.B) {
+	// Adding buffers has no effect.
+	cakeshop := defaults
+	cakeshop.BakeBuf = 10
+	cakeshop.IceBuf = 10
+	cakeshop.Work(b.N) // 224 ms
+}
+
+func BenchmarkVariable(b *testing.B) {
+	// Adding variability to rate of each step
+	// increases total time due to channel delays.
+	cakeshop := defaults
+	cakeshop.BakeStdDev = cakeshop.BakeTime / 4
+	cakeshop.IceStdDev = cakeshop.IceTime / 4
+	cakeshop.InscribeStdDev = cakeshop.InscribeTime / 4
+	cakeshop.Work(b.N) // 259 ms
+}
+
+func BenchmarkVariableBuffers(b *testing.B) {
+	// Adding channel buffers reduces
+	// delays resulting from variability.
+	cakeshop := defaults
+	cakeshop.BakeStdDev = cakeshop.BakeTime / 4
+	cakeshop.IceStdDev = cakeshop.IceTime / 4
+	cakeshop.InscribeStdDev = cakeshop.InscribeTime / 4
+	cakeshop.BakeBuf = 10
+	cakeshop.IceBuf = 10
+	cakeshop.Work(b.N) // 244 ms
+}
+
+func BenchmarkSlowIcing(b *testing.B) {
+	// Making the middle stage slower
+	// adds directly to the critical path.
+	cakeshop := defaults
+	cakeshop.IceTime = 50 * time.Millisecond
+	cakeshop.Work(b.N) // 1.032 s
+}
+
+func BenchmarkSlowIcingManyIcers(b *testing.B) {
+	// Adding more icing cooks reduces the cost of icing
+	// to its sequential component, following Amdahl's Law.
+	cakeshop := defaults
+	cakeshop.IceTime = 50 * time.Millisecond
+	cakeshop.NumIcers = 5
+	cakeshop.Work(b.N) // 288ms
+}