Golang ProgramsGolang Programs

This sample program demonstrates how to create multiple goroutines and how the goroutine scheduler behaves with three logical processors.

The Go standard library has a function called GOMAXPROCS in the runtime package that allows us to specify the number of logical processors to be used by the scheduler.
// This sample program demonstrates how to create goroutines and
// how the goroutine scheduler behaves with three logical processors.

package main

import (
	"fmt"
	"runtime"
	"sync"
)

func main() {
	// Allocate three logical processors for the scheduler to use.
	runtime.GOMAXPROCS(3)

	// processTest is used to wait for the program to finish.
	var processTest sync.WaitGroup
	// Add a count of three, one for each goroutine.
	processTest.Add(3)
	
	// Declaration of three anonymous function and create a goroutine.
	go func() {
		defer processTest.Done()
		for i := 0; i < 30; i++ {
			for j := 51; j <= 100; j++ {
				fmt.Printf(" %d", j)
				if j == 100{
					fmt.Println()
				}
			}
		}
	}()
	go func() {
		defer processTest.Done()
		for j := 0; j < 10; j++ {
			for char := 'A'; char < 'A'+26; char++ {
				fmt.Printf("%c ", char)
				if char == 'Z' {
					fmt.Println()
				}

			}
		}
	}()
	go func() {
		defer processTest.Done()
		for i := 0; i < 30; i++ {
			for j := 0; j <= 50; j++ {
				fmt.Printf(" %d", j)
				if j == 50 {
					fmt.Println()
				}
			}
		}
	}()

	// Wait for the goroutines to finish.
	processTest.Wait()	
}
If we give the scheduler more than one logical processor to use, we’ll see different behavior in the output of our example programs. If you run the program, you’ll see that the goroutines are running in parallel. Multiple goroutines start running, and the letters and numbers in the display are mixed. The output is based on running the program on an eight-core machine, so each goroutine is running on its own core.