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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
// See page 234.
// Package cake provides a simulation of
// a concurrent cake shop with numerous parameters.
//
// Use this command to run the benchmarks:
// $ go test -bench=. gopl.io/ch8/cake
package cake
import (
"fmt"
"math/rand"
"time"
)
type Shop struct {
Verbose bool
Cakes int // number of cakes to bake
BakeTime time.Duration // time to bake one cake
BakeStdDev time.Duration // standard deviation of baking time
BakeBuf int // buffer slots between baking and icing
NumIcers int // number of cooks doing icing
IceTime time.Duration // time to ice one cake
IceStdDev time.Duration // standard deviation of icing time
IceBuf int // buffer slots between icing and inscribing
InscribeTime time.Duration // time to inscribe one cake
InscribeStdDev time.Duration // standard deviation of inscribing time
}
type cake int
func (s *Shop) baker(baked chan<- cake) {
for i := 0; i < s.Cakes; i++ {
c := cake(i)
if s.Verbose {
fmt.Println("baking", c)
}
work(s.BakeTime, s.BakeStdDev)
baked <- c
}
close(baked)
}
func (s *Shop) icer(iced chan<- cake, baked <-chan cake) {
for c := range baked {
if s.Verbose {
fmt.Println("icing", c)
}
work(s.IceTime, s.IceStdDev)
iced <- c
}
}
func (s *Shop) inscriber(iced <-chan cake) {
for i := 0; i < s.Cakes; i++ {
c := <-iced
if s.Verbose {
fmt.Println("inscribing", c)
}
work(s.InscribeTime, s.InscribeStdDev)
if s.Verbose {
fmt.Println("finished", c)
}
}
}
// Work runs the simulation 'runs' times.
func (s *Shop) Work(runs int) {
for run := 0; run < runs; run++ {
baked := make(chan cake, s.BakeBuf)
iced := make(chan cake, s.IceBuf)
go s.baker(baked)
for i := 0; i < s.NumIcers; i++ {
go s.icer(iced, baked)
}
s.inscriber(iced)
}
}
// work blocks the calling goroutine for a period of time
// that is normally distributed around d
// with a standard deviation of stddev.
func work(d, stddev time.Duration) {
delay := d + time.Duration(rand.NormFloat64()*float64(stddev))
time.Sleep(delay)
}
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