为什么 Golang for 循环比 Python for 循环慢？

Question

I have tested how golang performs on for loop

Just looping 50,000 times in python and golang and I found that it took 0.59 seconds in python while in golang it took 9.12 seconds

Can any experienced go developer tell me why Golang is too slow at for loop while it's a compiled language?

import (
    "fmt"
    "time"
)
func main()  {
    start := time.Now()

    for i := 0; i < 50000; i++ {
         fmt.Println("Index", i)
    }

    finish := time.Now().Sub(start).Seconds()
    fmt.Printf("Elapsed time was %.2f seconds.\n", finish)
}

Answer 1

You're not measuring what you think you're measuring, that's why you're getting "surprising" results.

You're timing how long it takes to format and print a string, rather than "how fast a for loop is".

Also, keep in mind that measuring how long it takes to print something depends not only on how the code gets compiled / interpreted, but also on where exactly you're printing: I/O performance depends on things that are beyond your program (maybe the OS, maybe some physical device etc).

Finally, if you tried to microbenchmark the performance of a loop that does absolutely nothing, a compiler could be able to detect that and simply optimize the loop out completely, leaving you with not measuring anything...

These micro-benchmarks in isolation are, most of the time, not useful. If you want to compare Python vs Go in terms of performance, it's usually a better idea to test on a real problem rather than something artificial. And then compare not only the raw performance, but also other characteristics of the code quality in general.

The bottom line is that there's too much wrong with this benchmark to get any useful conclusions.