使用WaitGroup但没有使用通道的Golang死锁错误。

huangapple
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英文:

golang deadlock error with waitgroups but no channels

问题

我是你的中文翻译助手，以下是翻译好的内容：

我刚开始学习Go语言。我有一个关于矩阵及其运算的项目。我需要在我的乘法函数中使用goroutine（免责声明：这不是我的代码，这是一个小组项目，我需要在函数中添加goroutine）。
我在网上搜索了一些方法（我使用的方法），但是我遇到了一个致命错误：所有的goroutine都处于休眠状态，死锁！或者代码运行时间太长。

这是乘法函数的代码：

  1. func (M Matrix) Multiply(N Matrix) Matrix {
  2. 	var ans = BuildZeroMatrix(len(M), len(N[0]))
  3. 	var wg sync.WaitGroup
  4. 	wg.Add(len(M) * len(N[0]) * len(N))
  5. 	for i := 0; i < len(M); i++ {
  6. 		for j := 0; j < len(N[0]); j++ {
  7. 			for k := 0; k < len(N); k++ {
  8. 				wg.Add(1)
  9. 				go func(j int, i int, k int) {
  10. 					ans[i][j] += M[i][k] * N[k][j]
  11. 					defer wg.Done()
  12. 				}(j, i, k)
  13. 			}
  14. 		}
  15. 	}
  16. 	go func() {
  17. 		wg.Wait()
  18. 	}()
  19. 	return ans
  20. }

这是乘法函数。

  1. type Matrix [][]float64

这是Matrix类型。

  1. func BuildZeroMatrix(Row int, Col int) Matrix {
  2. 	var temp [][]float64
  3. 	for i := 0; i < Row; i++ {
  4. 		var tmp []float64
  5. 		for j := 0; j < Col; j++ {
  6. 			tmp = append(tmp, 0)
  7. 		}
  8. 		temp = append(temp, tmp)
  9. 	}
  10. 	M, _ := BuildMatrix(Row, Col, temp)
  11. 	return M
  12. }

这是BuildZeroMatrix函数。
我给这个函数传入了两个500*500的矩阵，它需要大约10秒才能运行完毕，或者会出现致命错误。
我在解决这个问题的过程中找到的每篇帖子都涉及到通道（channel），但是我没有使用通道。

英文:

im new to go. i have this project it's about matrices and their operations. i am supposed to use goroutine in my multiply function.(also disclaimer:this is not my code, its a group project im supposed to add the goroutine to the function)
i've searched around and seen this way(the way that i used) in different sites.however i get a fatal error: all the goroutines are asleep.deadlock!
or it just takes way too long for the code to run.

  2.     func (M Matrix) Multiply(N Matrix) Matrix {
  3.     	var ans  = BuildZeroMatrix(len(M), len(N[0]))
  4.     	var wg sync.WaitGroup
  5.     	wg.Add(len(M)*len(N[0])*len(N))
  6.     	for i := 0; i &lt; len(M); i++ {
  7.     		for j := 0; j &lt; len(N[0]); j++ {
  8.     			for k := 0; k &lt; len(N); k++ {
  9.     				wg.Add(1)
  10.     				go func(j int, i int, k int) {
  11.     					ans[i][j] += M[i][k] * N[k][j]
  12.     					defer wg.Done()
  13.     				}(j, i, k)
  14.     			}
  15.     		}
  16.     	}
  17.     	go func(){
  18.     		wg.Wait()
  20.     	}()
  21.     	return ans
  22.     }

this is the multiply function.

  1. type Matrix [][]float64

this is Matrix.

  2.     func BuildZeroMatrix(Row int, Col int) Matrix {
  3.     	var temp [][]float64
  4.     	for i := 0; i &lt; Row; i++ {
  5.     		var tmp []float64
  6.     		for j := 0; j &lt; Col; j++ {
  7.     			tmp = append(tmp, 0)
  8.     		}
  9.     		temp = append(temp, tmp)
  10.     	}
  11.     	M, _ := BuildMatrix(Row, Col, temp)
  12.     	return M
  13.     }

and this is the buildzeromatrix function.
i give the function 2 500*500 matrices and it takes about 10 seconds to run or it gives the fatal error.
every post i found on this problem had channels in them and their problem was with the channel.however i dont have any.

答案1

得分: 2

只是指出这段代码中的错误。请检查内联注释。

  1. func (M Matrix) Multiply(N Matrix) Matrix {
  2.     var ans  = BuildZeroMatrix(len(M), len(N[0]))
  3.     var wg sync.WaitGroup
  4.     wg.Add(len(M)*len(N[0])*len(N)) // 这是不必要的。你已经在 k 循环内添加了 goroutine。
  5.     for i := 0; i < len(M); i++ {
  6.         for j := 0; j < len(N[0]); j++ {
  7.             for k := 0; k < len(N); k++ {
  8.                 wg.Add(1)
  9.                 go func(j int, i int, k int) {
  10.                     ans[i][j] += M[i][k] * N[k][j] // 这是数据竞争区域。多个 goroutine 将尝试写入同一地址。你需要在这里加锁。
  11.                     defer wg.Done()
  12.                 }(j, i, k)
  13.             }
  14.         }
  15.     }
  16.     go func(){
  17.         wg.Wait() // 不应该在 goroutine 内部等待 goroutine 完成。因为在这里你不等待这个 goroutine 完成。
  18.     }()
  19.     return ans
  20. }

更新： 请检查示例代码

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"sync"
  6. )
  8. type Matrix [][]float64
  10. func (M Matrix) Multiply(N Matrix) Matrix {
  11. 	var ans = BuildZeroMatrix(len(M), len(N[0]))
  12. 	var wg sync.WaitGroup
  13. 	var mx sync.Mutex
  14. 	for i := 0; i < len(M); i++ {
  15. 		for j := 0; j < len(N[0]); j++ {
  16. 			for k := 0; k < len(N); k++ {
  17. 				wg.Add(1)
  18. 				go func(j int, i int, k int) {
  19. 					defer wg.Done()
  20. 					mx.Lock()
  21. 					ans[i][j] += M[i][k] * N[k][j]
  22. 					mx.Unlock()
  23. 				}(j, i, k)
  24. 			}
  25. 		}
  26. 	}
  27. 	wg.Wait()
  28. 	return ans
  29. }
  30. func BuildZeroMatrix(Row int, Col int) Matrix {
  31. 	var temp [][]float64
  32. 	for i := 0; i < Row; i++ {
  33. 		var tmp []float64
  34. 		for j := 0; j < Col; j++ {
  35. 			tmp = append(tmp, 0)
  36. 		}
  37. 		temp = append(temp, tmp)
  38. 	}
  39. 	return temp
  40. }
  42. func main() {
  43. 	var m, n Matrix
  45. 	// T1:
  46. 	m = Matrix{[]float64{1, 1, 1}, []float64{1, 1, 1}, []float64{1, 1, 1}}
  47. 	n = Matrix{[]float64{1, 1, 1}, []float64{1, 1, 1}, []float64{1, 1, 1}}
  48. 	fmt.Printf("%v", m.Multiply(n))
  50. 	// T2:
  51. 	m = Matrix{[]float64{1, 1, 1}, []float64{1, 1, 1}, []float64{1, 1, 1}}
  52. 	n = Matrix{[]float64{1, 1}, []float64{1, 1}, []float64{1, 1}}
  53. 	fmt.Printf("\n%v", m.Multiply(n))
  54. }
英文:

Just pointing out the mistakes in this snippet. Please check the inline comments.

  1. func (M Matrix) Multiply(N Matrix) Matrix {
  2.     var ans  = BuildZeroMatrix(len(M), len(N[0]))
  3.     var wg sync.WaitGroup
  4.     wg.Add(len(M)*len(N[0])*len(N)) // This is unnecessary. You are already adding the goroutine inside the k loop.
  5.     for i := 0; i &lt; len(M); i++ {
  6.         for j := 0; j &lt; len(N[0]); j++ {
  7.             for k := 0; k &lt; len(N); k++ {
  8.                 wg.Add(1)
  9.                 go func(j int, i int, k int) {
  10.                     ans[i][j] += M[i][k] * N[k][j] // This is data race area. Multiple goroutines will try to write to the same address. You will need a lock here.
  11.                     defer wg.Done()
  12.                 }(j, i, k)
  13.             }
  14.         }
  15.     }
  16.     go func(){
  17.         wg.Wait() // Wait()ing for goroutines to be completed should not be done inside a goroutine. Because here you don&#39;t wait for this goroutine to be done.
  18.     }()
  19.     return ans
  20. }

UPDATED: Pls check the sample code

  1. package main
  3. import (
  4. 	&quot;fmt&quot;
  5. 	&quot;sync&quot;
  6. )
  8. type Matrix [][]float64
  10. func (M Matrix) Multiply(N Matrix) Matrix {
  11. 	var ans = BuildZeroMatrix(len(M), len(N[0]))
  12. 	var wg sync.WaitGroup
  13. 	var mx sync.Mutex
  14. 	for i := 0; i &lt; len(M); i++ {
  15. 		for j := 0; j &lt; len(N[0]); j++ {
  16. 			for k := 0; k &lt; len(N); k++ {
  17. 				wg.Add(1)
  18. 				go func(j int, i int, k int) {
  19. 					defer wg.Done()
  20. 					mx.Lock()
  21. 					ans[i][j] += M[i][k] * N[k][j]
  22. 					mx.Unlock()
  23. 				}(j, i, k)
  24. 			}
  25. 		}
  26. 	}
  27. 	wg.Wait()
  28. 	return ans
  29. }
  30. func BuildZeroMatrix(Row int, Col int) Matrix {
  31. 	var temp [][]float64
  32. 	for i := 0; i &lt; Row; i++ {
  33. 		var tmp []float64
  34. 		for j := 0; j &lt; Col; j++ {
  35. 			tmp = append(tmp, 0)
  36. 		}
  37. 		temp = append(temp, tmp)
  38. 	}
  39. 	return temp
  40. }
  42. func main() {
  43. 	var m, n Matrix
  45. 	// T1:
  46. 	m = Matrix{[]float64{1, 1, 1}, []float64{1, 1, 1}, []float64{1, 1, 1}}
  47. 	n = Matrix{[]float64{1, 1, 1}, []float64{1, 1, 1}, []float64{1, 1, 1}}
  48. 	fmt.Printf(&quot;%v&quot;, m.Multiply(n))
  50. 	// T2:
  51. 	m = Matrix{[]float64{1, 1, 1}, []float64{1, 1, 1}, []float64{1, 1, 1}}
  52. 	n = Matrix{[]float64{1, 1}, []float64{1, 1}, []float64{1, 1}}
  53. 	fmt.Printf(&quot;\n%v&quot;, m.Multiply(n))
  54. }

huangapple
  • 本文由 发表于 2022年3月8日 17:20:41
  • 转载请务必保留本文链接：https://go.coder-hub.com/71392611.html
  • deadlock
  • go
  • goland
  • goroutine
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