// access to shared memory among threads
// controlled using atomics.
// For this program (and many like it) atomics are far
// preferable to locks (faster and less error prone)
//
// The basic idea here is to start a bunch of thread and
// have them all increment a single variable
//
// This version differs from the standard in the timing of the
// the update of the shared memory. In his case only
// update at the end of the run.
//
// Author:  gtowell
// Created: August 2022

package main

import (
	"fmt"
	"sync"
	"sync/atomic"
)
var (
	counter int64
)
func main()  {
	var wg sync.WaitGroup
	var threads int64 = 100
	var times int64 = 100000000
	var rz int64
	for rz=0; rz<threads; rz++ {
		wg.Add(1)
		go func(_rr int64) {
			defer wg.Done()
			var th int64
			var sm int64
			for th=1; th<=times; th++ {
				sm += th
			}
			atomic.AddInt64(&counter,sm)
		}(rz)
	}
	wg.Wait()
	fmt.Printf("summer done   %v\n", counter);	
}