dongque4778 2015-12-14 22:32

# 执行-编译一组函数时出错

I'm trying to implement a very simple test function to verify results coming from my solutions for Euler problems.

In the following code I've created a map of slices where on the index 0, I call the function which return a integer and on the index 1, the result I expect from that function.

``````package euler

import "testing"

func TestEulers(t *testing.T) {

tests := map[string][]int{
"Euler1": {Euler1(), 233168},
"Euler2": {Euler2(), 4613732},
"Euler3": {Euler3(), 6857},
"Euler4": {Euler4(), 906609},
"Euler5": {Euler5(), 232792560},
"Euler6": {Euler6(), 25164150},
}

for key, value := range tests {
if value[0] != value[1] {
t.Errorf("%s
Expected: %d
Got:%d",
key, value[0], value[1])
}
}
}
``````

For that map, every function works fine and return the result I expect if I run one by one or if I comment, let's say, half part of those keys/values.

For example, if I call the the function above with these lines commented the test will PASS.

``````tests := map[string][]int{
"Euler1": {Euler1(), 233168},
// "Euler2": {Euler2(), 4613732},
"Euler3": {Euler3(), 6857},
"Euler4": {Euler4(), 906609},
// "Euler5": {Euler5(), 232792560},
// "Euler6": {Euler6(), 25164150},
}
``````

But if I arrange the comments on that next way, for example, the test wouldn't.

``````tests := map[string][]int{
//"Euler1": {Euler1(), 233168},
"Euler2": {Euler2(), 4613732},
"Euler3": {Euler3(), 6857},
"Euler4": {Euler4(), 906609},
//"Euler5": {Euler5(), 232792560},
// "Euler6": {Euler6(), 25164150},
}
``````

The test will give me an error:

``````    WARNING: DATA RACE
Write by goroutine 6:
runtime.closechan()
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/runtime/chan.go:295 +0x0
github.com/alesr/project-euler.Euler2()
/Users/Alessandro/GO/src/github.com/alesr/project-euler/euler.go:40 +0xd7
github.com/alesr/project-euler.TestEulers()
/Users/Alessandro/GO/src/github.com/alesr/project-euler/euler_test.go:9 +0x46
testing.tRunner()
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/testing/testing.go:456 +0xdc

runtime.chansend()
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/runtime/chan.go:107 +0x0
github.com/alesr/numbers.FibonacciGen.func1()
/Users/Alessandro/GO/src/github.com/alesr/numbers/numbers.go:103 +0x59

Goroutine 6 (running) created at:
testing.RunTests()
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/testing/testing.go:561 +0xaa3
testing.(*M).Run()
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/testing/testing.go:494 +0xe4
main.main()
github.com/alesr/project-euler/_test/_testmain.go:54 +0x20f

Goroutine 7 (running) created at:
github.com/alesr/numbers.FibonacciGen()
/Users/Alessandro/GO/src/github.com/alesr/numbers/numbers.go:105 +0x60
github.com/alesr/project-euler.Euler2()
/Users/Alessandro/GO/src/github.com/alesr/project-euler/euler.go:27 +0x32
github.com/alesr/project-euler.TestEulers()
/Users/Alessandro/GO/src/github.com/alesr/project-euler/euler_test.go:9 +0x46
testing.tRunner()
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/testing/testing.go:456 +0xdc
==================
panic: send on closed channel

goroutine 36 [running]:
github.com/alesr/numbers.FibonacciGen.func1(0xc8200a01e0)
/Users/Alessandro/GO/src/github.com/alesr/numbers/numbers.go:103 +0x5a
created by github.com/alesr/numbers.FibonacciGen
/Users/Alessandro/GO/src/github.com/alesr/numbers/numbers.go:105 +0x61

testing.RunTests(0x24d038, 0x2f7340, 0x1, 0x1, 0xf78401)
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/testing/testing.go:562 +0xafa
testing.(*M).Run(0xc82004df00, 0x1ff0e8)
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/testing/testing.go:494 +0xe5
main.main()
github.com/alesr/project-euler/_test/_testmain.go:54 +0x210

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/runtime/asm_amd64.s:1696 +0x1

goroutine 35 [runnable]:
github.com/alesr/strings.Flip(0xc8200727a0, 0x6, 0x0, 0x0)
/Users/Alessandro/GO/src/github.com/alesr/strings/strings.go:33 +0x17e
github.com/alesr/project-euler.Euler4(0x1ac9)
/Users/Alessandro/GO/src/github.com/alesr/project-euler/euler.go:73 +0x95
github.com/alesr/project-euler.TestEulers(0xc8200b6000)
/Users/Alessandro/GO/src/github.com/alesr/project-euler/euler_test.go:11 +0x63
testing.tRunner(0xc8200b6000, 0x2f7340)
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/testing/testing.go:456 +0xdd
created by testing.RunTests
/private/var/folders/q8/bf_4b1ts2zj0l7b0p1dv36lr0000gp/T/workdir/go/src/testing/testing.go:561 +0xaa4
exit status 2
FAIL    github.com/alesr/project-euler  0.022s
``````

But still, I checked every single function and they work just as expected. You can access the Euler source code or the packages numbers and strings if you want.

At Euler2 function I have a defer statement to close the channel which is receiving from FibonacciGen.

And on FibonacciGen I do have another defer statement to close the same channel.

It seems that's the my first error. I should have just one and not two statements to close the channel, since they are trying to close the same thing. Is that correct?

Second (and here I'm even a little more unsure), the defer statement will prevent the function to be called until the main goroutine returns, right? Independently if I call it on the package main or not?

Plus, since the data is flowing through the channel from FibonacciGen to the main function. It seems for me, that if I close the channel at FibonacciGen I don't need to notify the main function. But If I close the channel on the main function I do have to notify FibonacciGen to stop trying to send to this channel.

• 写回答

#### 2条回答默认 最新

• 普通网友 2015-12-19 23:18
关注

Thank you all. With your help I could understand that I was closing the channel in the wrong way.

Now works correctly.

``````func Euler2() int {

c := make(chan int)
done := make(chan bool)

go numbers.FibonacciGen(c, done)

sum := 0
var f int

for {
f = <-c
if f < 4000000 {
if f%2 == 0 {
sum += f
}
} else {
close(done)
return sum
}
}
}

func FibonacciGen(c chan int, done chan bool) {

for {
select {
case <-done:
return
default:
for i, j := 0, 1; ; i, j = i+j, i {
c <- i
}
}
}

}
``````
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