On Friday, 4 August 2017 15:46:39 UTC+10, Evan Leis wrote:
>
> I ran into this same problem, and found this post!
> It looks like you're making the same simple mistake I was:
>
> # erroneous:
> defer f.Close()
> defer trace.Stop()
>
Defers run in LIFO order. This sample will call trace.Stop, then f.Close().
>
> You must stop the trace *before* closing the output file.
>
> # corrected:
> defer func() {
> trace.Stop()
> panic(f.Close()) # Be sure to handle file-closing errors. They're
> important!!
> }
>
This sample will panic the program every time
>
> On Tuesday, October 11, 2016 at 8:21:17 AM UTC-6, xavier zebier wrote:
>>
>> Hello,
>> I m trying to use the go tool trace. My code is
>>
>>
>> package main
>>
>> import (
>> "flag"
>> "fmt"
>> "math"
>> "net/http"
>> "os"
>> "runtime"
>> "runtime/trace"
>> "time"
>> )
>>
>> func indexHandler(w http.ResponseWriter, r *http.Request) {
>> primesInRangeParallel(10, 64)
>> fmt.Fprintf(w, "hello world, I'm running on %s with an %s CPU ",
>> runtime.GOOS, runtime.GOARCH)
>>
>> }
>>
>> func main() {
>> flag.Parse()
>> f, errs := os.Create(time.Now().Format("2006-01-02T150405.out"))
>> if errs != nil {
>> panic(errs)
>> }
>>
>> if err := trace.Start(f); err != nil {
>> panic(err)
>> }
>>
>> defer f.Close()
>> defer trace.Stop()
>> http.HandleFunc("/", indexHandler)
>>
>> http.ListenAndServe(":8080", nil)
>> }
>>
>> // We will use this struct to communicate results via a channel
>> type PrimeResult struct {
>> number int64 // A number
>> prime bool // Is prime or not
>> }
>>
>> /**
>> * A function to return a prime calculation over a channel. This way
>> * we don't need to have 2 versions of isPrime function, one for
>> * sequential calculations and another for paralel
>> */
>>
>> func isPrimeAsync(number int64, channel chan PrimeResult) {
>>
>> result := new(PrimeResult)
>> result.number = number
>> result.prime = isPrime(number)
>> channel <- *result
>> }
>>
>> /**
>> * Accepts a range of integers [min, max] and a channel and it executes
>> * in PARALEL the processes that check if a number is prime or not.
>> *
>> * This function does nothing with the result. In another point, somebody
>> * will have to read the channel and process the results
>> */
>> func firePrimeCalculations(min int64, max int64, channel chan
>> PrimeResult) {
>> var i int64
>> for i = min; i <= max; i++ {
>> go isPrimeAsync(i, channel)
>> }
>> }
>>
>> /**
>> * Accepts a range of integers [min, max] and
>> * returns an array with all the prime numbers in this range.
>> *
>> * Execution is done in paralel. First it fires all the
>> * processes that check for a prime number. These processes
>> * will write the result in a channel.
>> *
>> * We will receive the results over this channel creating the
>> * list of prime numbers and returning it
>> *
>> */
>>
>> func primesInRangeParallel(min int64, max int64) []int64 {
>> var primeNumbers []int64
>> var res PrimeResult
>> var prev int64
>>
>> channel := make(chan PrimeResult)
>> defer close(channel)
>>
>> go firePrimeCalculations(min, max, channel)
>>
>> prev = 0
>> for i := min; i <= max; i++ {
>> res = <-channel
>> if res.prime {
>> primeNumbers = append(primeNumbers, res.number)
>>
>> done := 100 * (i - min) / (max - min)
>> if prev != done {
>> fmt.Printf("%d %% done.\n", done)
>> prev = done
>> }
>> }
>> }
>> return primeNumbers
>> }
>> func isPrime(candidate int64) bool {
>> var i, limit int64
>>
>> if candidate == 2 {
>> return true
>> }
>>
>> if math.Mod(float64(candidate), 2) == 0 {
>> return false
>> }
>>
>> limit = int64(math.Ceil(math.Sqrt(float64(candidate))))
>> for i = 3; i <= limit; i += 2 { //Only odd numbers
>> if math.Mod(float64(candidate), float64(i)) == 0 {
>> return false
>> }
>> }
>> return true
>> }
>>
>> The prime number calculation is basically there to get some calculation.
>>
>> My go env command gives :
>>
>> C:\repo\gonew\src\github.com\tixu\trace>go env
>> set GOARCH=amd64
>> set GOBIN=
>> set GOEXE=.exe
>> set GOHOSTARCH=amd64
>> set GOHOSTOS=windows
>> set GOOS=windows
>> set GOPATH=c:\repo\gonew
>> set GORACE=
>> set GOROOT=C:\Go
>> set GOTOOLDIR=C:\Go\pkg\tool\windows_amd64
>> set CC=gcc
>> set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0
>> set CXX=g++
>> set CGO_ENABLED=1
>>
>>
>>
>> And I get the following error :
>>
>> C:\repo\gonew\src\github.com\tixu\trace>go tool trace Trace
>> 2016-10-11T153554.out
>> 2016/10/11 15:36:45 Parsing trace...
>> failed to parse trace: no EvFrequency event
>>
>> Can you help me .?
>>
>> Thanks in advance,
>>
>> Xavier
>>
>
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