func TestSieve(t *testing.T) {

func TestJustSieve(t *testing.T) {

func TestConcSieve(t *testing.T) {
	is := is.New(t)
	for _, tc := range sieveCases {
		is.Equal(tc.expected, primes.ConcurrentSieve(tc.input))
	}
}

func BenchmarkSieve(b *testing.B) {

func BenchmarkJustSieve(b *testing.B) {

	}
}
func BenchmarkConcurrentSieve(b *testing.B) {
	for i := 0; i < b.N; i++ {
		primes.ConcurrentSieve(1e6)

	"sync"

func ConcurrentSieve(limit int) []bool {
	sieve := make([]bool, limit+1)
	wg := new(sync.WaitGroup)
	wg.Add(1)
	go func() {
		// handle even numbers
		for i := 2 * 2; i <= limit; i += 2 {
			sieve[i] = true
		}
		wg.Done()
	}()
	for p := 3; p*p <= limit; p += 2 {
		wg.Add(1)
		go func(p int) {
			if !sieve[p] {
				for i := p * p; i <= limit; i += p {
					sieve[i] = true
				}
			}
			wg.Done()
		}(p)
	}
	wg.Wait()
	return sieve
}