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Comment by akc | Hacker News Reader

What do rendering times in Go look like, compared to a similar C implementation?

I don't have anything to compare to, but Go seems quite fast. I would guess no worse than 2x C in this case, but I'm pulling that number out of my butt.

Actually I was originally going to write this in C but it started to be a PITA and I had the spontaneous idea that maybe Go would be the right choice for this (never used it before). It totally was. No way I would've had this level of results so quickly in C.

Being a big fan of Python and C, Go seems like a really good middle ground. Really happy to have learned it.

I took a look at your code as I've been writing go for side projects for the last few months and like to compare styles.

You nailed the idiomatic go approach to development imho. Very nice.

I'm very very impressed by your code quality especially when this is just your first Go project. I'm an experienced Go developer btw. You're just so good.

As someone trying to learn the basics of rendering, I was really pleased to see your project pop up on the github explore email today. It's very easy to follow, even for a non-Go programmer like me.

Performance question from a no-Go programmer though - does returning objects from functions incur a cost? For example "func Reflect() Ray {}" or "func Add() Vector" - do they create a new object on the heap? If so is that an issue in Go?

I actually tried changing all of my Rays to *Rays, passing pointers instead of values, and it made no significant difference in rendering times.

One interesting benefit I see is the ability to easily parallelize the work. Take a look at the render implementation here - https://github.com/fogleman/pt/blob/master/pt/render.go#L28

It was SO easy! The only tricks were GOMAXPROCS and not using the shared rand functions because they are synchronized.

I'm interested in more information about why you decided to alter GOMAXPROCS and what your results were from testing.

I've had a play with this myself and found that it cause sporadic and unpredictable crashing (very different style of application though - I was building a webserver). However this was an earlier iteration of Go (possibly Go 1.1 but likely 1.2) so things may have improved since then, or you might have found a saner way of tweaking it.

I have zero experience with rendering but I have never had an issue adjusting GOMAXPROCS for web apps.

When GOMAXPROCS > 1, your program goes from "everything is executed sequentially" to "everything is maybe executed in parallel." This can expose data race bugs in your code that aren't present when GOMAXPROCS = 1.

(I'd suggest using Go's race detector.)

You know, that's entirely possible. I was playing around with different methods of passing data between goroutines for increasing performance and I knew one of the methods I was testing wasn't idiomatic Go. However since I wasn't getting race conditions normally i assumed that the GOMAXPROCS fault wasn't down to my shonky code.

The weird thing is I thought I'd read somewhere that said Go defaulted to a process per CPU core (like the OP has hardcoded ib this project). I'm guessing that isn't the case then? It sadly wouldn't be the first time I've misread something! :(

GOMAXPROCS defaults to 1, meaning unless you change that value, your code will not run in parallel by default.

Have a look at http://kidoman.io/programming/go-getter-part-3.html

Did this last year comparing Go 1.2 with C/C++ (and lots of other languages contributed by others.)

The original version: http://kidoman.io/programming/go-getter.html

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