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  1. package main
  2. import "fmt"
  3.  
  4. // Send the sequence 2, 3, 4, ... to channel 'ch'
  5. func Generate(ch chan<- int) {
  6. 	for i := 2; ; i++ {
  7. 		ch <- i    // Send 'i' to channel 'ch'
  8. 	}
  9. }
  10.  
  11. // Copy the values from channel 'in' to channel 'out',
  12. // removing the multiples of 'prime'.
  13. // 'in' assumed to send increasing numbers
  14. func Filter(in <-chan int, out chan<- int, prime int) {
  15. 	m := prime + prime
  16. 	for {
  17. 		i := <- in    // Receive value from 'in'
  18. 		for i > m {
  19. 			m = m + prime
  20. 		}
  21. 		if i < m {
  22. 			out <- i  // Send 'i' to 'out'
  23. 		}
  24. 	}
  25. }
  26.  
  27. // The prime sieve: Daisy-chain Filter processes
  28. func Sieve(out chan<- int) {
  29. 	ch := make(chan int)     // Create a new channel
  30. 	go Generate(ch)          // Launch Generate goroutine
  31. 	for  {
  32. 		prime := <-ch
  33. 		out <- prime
  34. 		ch1 := make(chan int)
  35. 		go Filter(ch, ch1, prime)
  36. 		ch = ch1
  37. 	}
  38. }
  39.  
  40. func main() {
  41. 	ch := make(chan int)     // Create a new channel
  42. 	go Sieve(ch)             // Launch Sieve goroutine
  43. 	m := 3000
  44. 	for i := 0; i < m; i++ {
  45. 		prime := <-ch
  46. 		if i >= (m-5) {
  47. 		    fmt.Printf("%4d ", prime)
  48. 		    //if (i+1)%10==0 {
  49. 			//	fmt.Println("")
  50. 		    //}
  51. 		}
  52. 	}
  53. }
  54. /*
  55. 3000:	time: 4.02 memory: 789504 signal:0   ---- n^2.1 ----
  56. 27409 27427 27431 27437 27449 
  57.  
  58. 2000:	time: 1.75 memory: 789504 signal:0   ---- n^2.1 ----
  59. 17359 17377 17383 17387 17389 
  60.  
  61. 1000:	time: 0.39 memory: 789504 signal:0     
  62. 7879 7883 7901 7907 7919 
  63. */
Success #stdin #stdout 4.02s 789504KB
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27409 27427 27431 27437 27449
https://ideone.com/ixhHNO
for http://r...content-available-to-author-only...e.org/wiki/Sieve_of_Eratosthenes#Concurrent_Daisy-chain_sieve
language:
Go (go 1.12.1)
created:
8 years ago
visibility:
public

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