Golang folks, after looking at the code, I am surprised and don't understand why Go version is slow compared to C/C++/Rust. Can anyone please explain? Thank you.

▲ zamadatix 7 months ago | parent | next [-]

Go's int defaults to 64 bits on a 64 bit machine while C/Rust/Java are all defaulting to 32 bit on the author's machine.

Editing the code and running local to get a difference factor, it looks like the same Go code with int takes 1.5x the amount of time as the int32 code on my machine. That puts it ~right next to Java (assuming the perf change maps 1:1). Remove the GC and it comes in ~right next to C++.

Looking at the compiler assembly output on Godbolt it's fun to see all the extra panic info and checks Go adds before going to the loop whereas the C just segfaults from blasting forward anyways, sometimes with no detail.

Anyways, that's why I don't like these types of "benchmarks" (micro tests made into a media post). By the time someone actually looks into them to see what's up everyone has already seen the results and moved on.

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iambvk 7 months ago | parent | next [-]

Thanks for this information. I wasn't aware that using 64-bit ints makes such a big difference in performance. Thank you.

	▲	zamadatix 7 months ago \| parent [-]
		Usually less on computation performance (often identical or very close to in raw cycle count for the operation) but more on cache/memory performance. The way that maps is platform specific of course.

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igouy 7 months ago | parent | prev [-]

> By the time someone actually looks into them to see what's up everyone has already seen the results and moved on.

Yep.

▲ vocx2tx 7 months ago | parent | prev | next [-]

64 bit mod is much slower than 32 bit mod. Your C program uses int32_t everywhere, while your Go program uses int (which is probably 64 bit on you machine); so this is not a fair comparison. Changing the Go program to use int32 everywhere makes it 35% faster on my machine.

▲ bddicken 7 months ago | parent | prev [-]

Author here: Yeah, I was surprised that there doesn't seem to be many options for extra optimizations in the Go compiler. Would be curious if Go experts have more insight or other compiler recommendations.

	▲	boyter 7 months ago \| parent \| next [-]
		I doubt its the GC kicking in, but you could run it with the following environment variable set just to ensure that its not doing anything. `GOGC=-1` EDIT: Trying it out quickly shows a small improvement actually, but so small as to likely be noise as I was doing other things on the machine. `Summary ./mainnogc 1000 ran 1.01 ± 0.06 times faster than ./maingc 1000`
	▲	Splizard 7 months ago \| parent \| prev [-]
		You've set the Go code to use int64 but the other faster implementations are using int32.