kconner

macOS Internals

Understand your Mac and iPhone more deeply by tracing the evolution of Mac OS X from prelease to Swift. John Siracusa delivers the details.

Starting Points

How to use this gist

You've got two main options:

djspiewak

Fibers

Fibers are an abstraction over sequential computation, similar to threads but at a higher level. There are two ways to think about this model: by example, and abstractly from first principles. We'll start with the example.

(credit here is very much due to Fabio Labella, who's incredible Scala World talk describes these ideas far better than I can)

Callback Sequentialization

Consider the following three functions

LukeMathWalker

name: Security audit
on:
  schedule:
    - cron: '0 0 * * *'
  push:
    paths:
      - '**/Cargo.toml'
      - '**/Cargo.lock'
jobs:
  security_audit:

BalmungSan

Polymorphism in Scala

This document aims to show and compare three alternatives for achieving polymorphism in Scala.

• Subtyping, common in object-oriented languages like Java.
• Duck typing, common in dynamically typed languages like Python.
• Typeclasses, common in functional languages like Haskell.

Additionally, when implementing the typeclass pattern in Scala,

djspiewak

Quick Tips for Fast Code on the JVM

I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.

This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea

djspiewak

Thread Pools

Thread pools on the JVM should usually be divided into the following three categories:

1. CPU-bound
2. Blocking IO
3. Non-blocking IO polling

Each of these categories has a different optimal configuration and usage pattern.

hanny24

// Simple Scala-like for comprehension for rust
macro_rules! comp(
	// base case, using "map"
	(val $id:ident <- $expr:expr $(,if $cond:expr)* $(,let $assign_id:pat = $assign_val:expr)* ,yield $comp:expr) =>
	(
		($expr)$(.filtered(|&$id| $cond))*.map(|&$id| {
			$(let $assign_id = $assign_val;)* $comp
			}
		)