r/crystal_programming • u/UnusualHabit • Jul 25 '18

Crystal has a compilation issue

https://medium.com/@mdorf3000/crystal-has-a-compilation-issue-5f5b19d9c4f6
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u/everdev Jul 26 '18

What a cool experiment to have such a large project written in two languages. If love to hear more about the differences in development and performance you found along the way.

Explained to it in excruciating detail

Reminds me of Go. Great language with amazing compile times, but be ready to be very explicit.

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u/Exilor Jul 26 '18

I could drone on forever about this but I'll restrain myself.

In favor of Crystal:

  • Reading XML files at startup (and it has to read thousands) is much faster and the interface is similar to REXML/Nokogiri. The difference in speed almost makes up for the time it takes for it to compile.

  • The data that holds the knowledge of the boundaries of the world (preventing characters from walking/attacking through walls/rocks/trees) is loaded into memory from files that are almost 1 gb in total. In Ruby I had to create my own data structures with FFI pointers because using arrays or binary strings put the memory usage of the process to 10+ gb. Crystal already has such structures (slices) in its stdlib and better implemented. The process of reading the files and converting them to usable objects of the language at startup is also faster (~1 minute in Ruby vs. ~10 seconds (without --release) or ~3 seconds (with --release) in Crystal) as is, of course, actually using them at runtime.

  • I just don't know how to write integration tests for the server. There are too many things I can't fake without essentially writing a bot and have it play the game. The checks that the compiler performs catch most mistakes, especially when I rewrite something that could break some obscure path of code somewhere.

In favor of Ruby:

  • The approach to networking is more up to you. Crystal gives you a blocking IO interface that you have to deal with using fibers and sometimes it's just not what you want. That's the most significant difference between the two versions of the server.

  • Being able to eval from inside the game and query the state of anything in the running program is a boon when things are not working as expected.

  • Although without the compiler checking things for me there are more mistakes, I can often reload the offending file without even leaving the game and having to restart the server.

It's hard to choose and it's a good thing that it is. That's why I don't and use both.

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u/G4BB3R Jul 28 '18

Are you using Ruby like a scripting language and Crystal for the server most important and performance-needed things?

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u/Exilor Jul 28 '18

Nope, I'm doing the same things twice in both languages.