Channel Pipeline

Channels can connect pipeline stages while each stage keeps a small, deterministic responsibility.
channel pipeline Start a producer goroutine, transform each value in the main goroutine, and join through channel close semantics.
                            count
                            count = 3 (default)count = 2count = 4
                        

                            channel_pipeline.go
                        
Replay: real traced execution (multi-file project)

                            package main

import "fmt"

func main() {
	var count = 3
	inputs := make(chan int)
	outputs := []int{}

	go func() {
		for value := 1; value <= count; value++ {
			inputs <- value
		}
		close(inputs)
	}()

	for value := range inputs {
		outputs = append(outputs, value*value)
	}

	total := 0
	for _, value := range outputs {
		total += value
	}

	fmt.Println("count=", count)
	fmt.Println("outputs=", outputs)
	fmt.Println("total=", total)
}
package main

import "fmt"

func main() {
	var count = 2
	inputs := make(chan int)
	outputs := []int{}

	go func() {
		for value := 1; value <= count; value++ {
			inputs <- value
		}
		close(inputs)
	}()

	for value := range inputs {
		outputs = append(outputs, value*value)
	}

	total := 0
	for _, value := range outputs {
		total += value
	}

	fmt.Println("count=", count)
	fmt.Println("outputs=", outputs)
	fmt.Println("total=", total)
}
package main

import "fmt"

func main() {
	var count = 4
	inputs := make(chan int)
	outputs := []int{}

	go func() {
		for value := 1; value <= count; value++ {
			inputs <- value
		}
		close(inputs)
	}()

	for value := range inputs {
		outputs = append(outputs, value*value)
	}

	total := 0
	for _, value := range outputs {
		total += value
	}

	fmt.Println("count=", count)
	fmt.Println("outputs=", outputs)
	fmt.Println("total=", total)
}

                        
1count ← 3, inputs ← (chan int)(⟨addr A⟩), outputs ← []int{}⋯5func main() {6  var count→ 3 = 3 //@count=2, 47  inputs→ (chan int)(⟨addr A⟩) := make(chan int)8  outputs→ []int{} := []int{}910  go func() {11    for value := 1; value <= count; value++ {12      inputs <- value13    }14    close(inputs)15  }()⋯
2for value := 1; value <= count; value++pass 1 of 3⋯10go func() {11  for value1 := 1; value <= count3; value++ {12    inputs(chan int)(⟨addr A⟩) <- value113  }⋯All 3 passes — pass 1 is the card abovepassvalue
11
22
33
3outputs ← []int{1}pass 1 of 3⋯17for value1 := range inputs(chan int)(⟨addr A⟩) {18  outputs→ []int{1} = append(outputs, value1*value)19}⋯All 3 passes — pass 1 is the card abovepassvalueoutputs
11[]int{} → []int{1}
22[]int{1} → []int{1, 4}
33[]int{1, 4} → []int{1, 4, 9}
4close(inputs)⋯13  }14  close(inputs(chan int)(⟨addr A⟩))15}()⋯
5total ← 0⋯21total→ 0 := 022for _, value := range outputs {⋯
6total ← 1pass 1 of 3⋯21total := 022for _, value1 := range outputs[]int{1, 4, 9} {23  total→ 1 += value124}⋯All 3 passes — pass 1 is the card abovepassvaluetotal
110 → 1
241 → 5
395 → 14
7fmt.Println("count=", count)⋯26  fmt.Println("count=", count3)27  fmt.Println("outputs=", outputs[]int{1, 4, 9})28  fmt.Println("total=", total14)29}⋯outputcount= 3
outputs= [1 4 9]
total= 14
1count ← 2, inputs ← (chan int)(⟨addr A⟩), outputs ← []int{}⋯5func main() {6  var count→ 2 = 27  inputs→ (chan int)(⟨addr A⟩) := make(chan int)8  outputs→ []int{} := []int{}910  go func() {11    for value := 1; value <= count; value++ {12      inputs <- value13    }14    close(inputs)15  }()⋯
2for value := 1; value <= count; value++pass 1 of 2⋯10go func() {11  for value1 := 1; value <= count2; value++ {12    inputs(chan int)(⟨addr A⟩) <- value113  }⋯
3for value := 1; value <= count; value++pass 2 of 2⋯10go func() {11  for value2 := 1; value <= count2; value++ {12    inputs(chan int)(⟨addr A⟩) <- value213  }⋯
4outputs ← []int{1}pass 1 of 2⋯17for value1 := range inputs(chan int)(⟨addr A⟩) {18  outputs→ []int{1} = append(outputs, value1*value)19}⋯
5outputs ← []int{1, 4}pass 2 of 2⋯11  for value := 1; value <= count; value++ {12    inputs(chan int)(⟨addr A⟩) <- value213  }14  close(inputs(chan int)(⟨addr A⟩))15}()1617for value2 := range inputs(chan int)(⟨addr A⟩) {18  outputs→ []int{1, 4} = append(outputs, value2*value)19}⋯
6total ← 0⋯21total→ 0 := 022for _, value := range outputs {⋯
7total ← 1pass 1 of 2⋯21total := 022for _, value1 := range outputs[]int{1, 4} {23  total→ 1 += value124}⋯
8total ← 5pass 2 of 2⋯21total := 022for _, value4 := range outputs[]int{1, 4} {23  total→ 5 += value424}⋯
9fmt.Println("count=", count)⋯26  fmt.Println("count=", count2)27  fmt.Println("outputs=", outputs[]int{1, 4})28  fmt.Println("total=", total5)29}⋯outputcount= 2
outputs= [1 4]
total= 5
1count ← 4, inputs ← (chan int)(⟨addr A⟩), outputs ← []int{}⋯5func main() {6  var count→ 4 = 47  inputs→ (chan int)(⟨addr A⟩) := make(chan int)8  outputs→ []int{} := []int{}910  go func() {11    for value := 1; value <= count; value++ {12      inputs <- value13    }14    close(inputs)15  }()⋯
2for value := 1; value <= count; value++pass 1 of 4⋯10go func() {11  for value1 := 1; value <= count4; value++ {12    inputs(chan int)(⟨addr A⟩) <- value113  }⋯All 4 passes — pass 1 is the card abovepassvalue
11
22
33
44
3outputs ← []int{1}pass 1 of 4⋯17for value1 := range inputs(chan int)(⟨addr A⟩) {18  outputs→ []int{1} = append(outputs, value1*value)19}⋯All 4 passes — pass 1 is the card abovepassvalueoutputs
11[]int{} → []int{1}
22[]int{1} → []int{1, 4}
33[]int{1, 4} → []int{1, 4, 9}
44[]int{1, 4, 9} → []int{1, 4, 9, 16}
4total ← 0⋯21total→ 0 := 022for _, value := range outputs {⋯
5total ← 1pass 1 of 4⋯21total := 022for _, value1 := range outputs[]int{1, 4, 9, 16} {23  total→ 1 += value124}⋯All 4 passes — pass 1 is the card abovepassvaluetotal
110 → 1
241 → 5
395 → 14
41614 → 30
6fmt.Println("count=", count)⋯26  fmt.Println("count=", count4)27  fmt.Println("outputs=", outputs[]int{1, 4, 9, 16})28  fmt.Println("total=", total30)29}⋯outputcount= 4
outputs= [1 4 9 16]
total= 30
pass	`value`	`outputs`
1	1	[]int{} → []int{1}
2	2	[]int{1} → []int{1, 4}
3	3	[]int{1, 4} → []int{1, 4, 9}