After I increase the dimension of matrixes to 1000x1000, the advantage of goroutines appears: using goroutines takes shorter time than not using them. Thanks for all your comments.
On Friday, February 19, 2021 at 11:37:39 PM UTC+8 meera wrote: > You can find what's the difference between the two programs yourself by > profiling it, it will show the overhead of context switch, goroutine > initialization, GC and so forth. > > Heres some good resources: > https://blog.golang.org/pprof > https://youtu.be/nok0aYiGiYA > > On Fri, 19 Feb 2021, 11:46 Yuwen Dai, <yuw...@gmail.com> wrote: > >> Hi experts, >> >> I'm a newbie to golang. One of my first ideas to use goroutine is to >> write a matrix multiplying programme: C = A*B. I though the calculating >> of every element of C: c[i][j] = row i of A * column j of B could be >> run by a goroutine. This is the skeleton of the code: >> >> t1 := time.Now().UnixNano() //benchmark >> rand.Seed(t1) >> for i := 0; i < n; i++ { >> ai,_ := get_row(a,i) >> for j := 0; j < t; j ++ { >> bj, _ := get_column(b,j) >> // c[i][j],_ = dot_product(ai, bj) >> go func(element *int, ai,bj []int) { >> *element,_ = dot_product(ai,bj) >> wg.Done() >> }(&c[i][j], ai, bj) >> } >> } >> >> wg.Wait() // waiting for all the elements have been calculated >> t2 := time.Now().UnixNano() >> fmt.Printf("the dot_product using goroutine costs %v\n", t2 - t1) >> >> As the goroutines will run "concurrently" on my laptop with 8 CPU cores >> to calculate the element of matrix, I thought the code would ran faster >> than not using goroutine. In fact, it ran slowlier than not using >> goroutine. Any explanation of this? By the way, the dimension of >> matrix is 100x100. >> >> Best regards, >> Yuwen >> >> -- >> > You received this message because you are subscribed to the Google Groups >> "golang-nuts" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to golang-nuts...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/52ef6c0f-7044-4b7e-968c-b894eb52d374n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/golang-nuts/52ef6c0f-7044-4b7e-968c-b894eb52d374n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/4c7c103a-0a4e-475c-9114-a8613d20e42cn%40googlegroups.com.
