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A Week with Go, Day 5

Concurrent programming in Go makes use of coroutines, which are quaintly called "goroutines", and channels. Coroutines are functions executed asynchronously from the rest of your program, and channels are synchronous pipes through which the routines communicate. I had written a multi-threaded Kember Identity program in C a while back, and decided to rewrite it in Go to gain some exposure working with these features.

The Effective Go primer gives a hint of what goes on under the hood with coroutines in Go.
A goroutine has a simple model: it is a function executing in parallel with other goroutines in the same address space. It is lightweight, costing little more than the allocation of stack space. And the stacks start small, so they are cheap, and grow by allocating (and freeing) heap storage as required.

Goroutines are multiplexed onto multiple OS threads so if one should block, such as while waiting for I/O, others continue to run. Their design hides many of the complexities of thread creation and management.
Indeed, Go does a wonderful job of hiding the complexities of working with threads. Spawning the coroutine is as simple as prefacing the function call with go.
go kemberTest(start, tmp, ch)
Writing and reading values to and from a channel is done with <-. Both are blocking operations, so you don't have to worry about manually fumbling with locks to synchronize routines. The primer has this to say about channels:
Channels combine communication—the exchange of a value—with synchronization—guaranteeing that two calculations (goroutines) are in a known state.
if hash == curr {
    fmt.Println(hash)
    ch <- true
    return
}
No muss, no fuss. Coroutines and channels work together to make concurrent programming a breeze! I sat down expecting to stumble through getting my threads to communicate properly, but to be honest I spent more time working out the correct type castings throughout the program than I spent on the concurrency piece.

The asynchronous nature of coroutines with the synchronous nature of channels make it easy to write generators, too.
func fib(ch chan int64) {
    var a, b int64 = 1, 2
    for {
        ch <- a
        a, b = b, a + b
    }
}

func main() {
    ch := make(chan int64)
    go fib(ch)
    for i := <- ch; i > 0; i = <- ch {
        fmt.Println(i)
    }
}
After spending a week with Go I formed some good opinions and some bad opinions. The language has a dynamic feel with := and garbage collection which is nice, though I would have liked to have seen some more type inference being done by the compiler. An OO model that's not focused on hierarchical inheritance is a welcome change. Go is still rough around the edges and I wouldn't consider it ready to be a full-time development language for production projects just yet, but it has come quite a long way in the past year... and will undoubtedly continue to mature rapidly as an open source project.

Google did a disservice to Go when the language was first released by placing so much emphasis on compilation speed. The tech pundits and skeptics were right in questioning whether the world needed yet another language just because the current ones compiled too slow. Compilation is a function of the compiler after all, so if that was really the problem then a more appropriate solution would be to write a new compiler! But the pundits were ignorant in dismissing Go and believing there was no room for a new language. They failed to see an opportunity to re-examine old beliefs and explore now constructs. Many more would have taken Go seriously out of the gate if Google and early developers had touted its OO model and goroutines/channels instead of its compilation speed.

I can see myself using Go for a few side projects here and there, and perhaps larger projects in the future. Perhaps I'm just not comfortable yet with garbage collection in real-time and system-level programming yet, but I don't see it replacing my use of C; I choose C when a major need of my program is speed or memory and the unpredictable nature of a garbage collector works against those. But Go would definitely be a good choice for problems now solved using Java.

Thanks for spending the week with me (and Go); feel free to share your impressions of Go in the comments below. If you're interested, here's my Kember Identity code.

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