jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

corsix

Exploiting Lua 5.1 on 32-bit Windows

The following Lua program generates a Lua bytecode program called ignore-unsigned-sga.fnt, which in turn loads a DLL from within an extremely locked down Lua 5.1 sandbox in a program called RelicCOH2.exe. The remainder of this document attempts to explain how this program works by a whirlwind tour of relevent bits of the Lua 5.1 virtual machine.

if string.dump(function()end):sub(1, 12) ~= "\27Lua\81\0\1\4\4\4\8\0" then
  error("This generator requires a 32-bit version of Lua 5.1")
end

local function outer()
  local magic -- In bytecode, the stack slot corresponding to this local is changed

AndrasKovacs

{-# LANGUAGE 
    LambdaCase, GADTs, TypeOperators, TypeFamilies, DataKinds #-}

data Type = TInt | TBool | Type :=> Type

-- Needs GHC >= 7.8
type family Interp (t :: Type) where
    Interp TInt      = Int
    Interp TBool     = Bool 
    Interp (a :=> b) = Interp a -> Interp b

jansegre

-- script.lua
-- Receives a table, returns the sum of its components.
io.write("The table the script received has:\n");
x = 0
for i = 1, #foo do
  print(i, foo[i])
  x = x + foo[i]
end
io.write("Returning data back to C\n");
return x

AlexBedley

![](http://dougbelshaw.com/blog/wp-content/uploads/2013/10/ship-it-squirrel.jpg)
![](http://shipitsquirrel.github.io/images/ship%20it%20squirrel.png)

blake-mealey

-- LICENSE
--
--   This software is dual-licensed to the public domain and under the following
--   license: you are granted a perpetual, irrevocable license to copy, modify,
--   publish, and distribute this file as you see fit.

-- VERSION 0.1.0

-- Author: Forrest Smith (github.com/forrestthewoods/lib_fts)
-- Translated to Lua by Blake Mealey (github.com/blake-mealey)

parkercoates

# GIT heart FZF
# -------------

is_in_git_repo() {
  git rev-parse HEAD > /dev/null 2>&1
}

gf() {
  is_in_git_repo || return
  git -c color.status=always status --short |

kconner

E017 DO YOU EXPECT ME TO FIGURE THIS OUT?
E079 PROGRAMMER IS INSUFFICIENTLY POLITE
E099 PROGRAMMER IS OVERLY POLITE
E111 COMMUNIST PLOT DETECTED, COMPILER IS SUICIDING
E123 PROGRAM HAS DISAPPEARED INTO THE BLACK LAGOON
E127 SAYING ’ABRACADABRA’ WITHOUT A MAGIC WAND WON’T DO YOU ANY GOOD
E129 PROGRAM HAS GOTTEN LOST
E139 I WASN’T PLANNING TO GO THERE ANYWAY
E182 YOU MUST LIKE THIS LABEL A LOT!
E197 SO! 65535 LABELS AREN’T ENOUGH FOR YOU?

chrisdone

Intro

I've been working on a parser for a Haskell-like syntax called Duet. In the implementation I've taken particular care to make an awesome tokenizer and parser that is super helpful to learners.

Jasper Van der Jeugt made a talk about producing good error messages recently, which coincides nicely with my parallel work on this. So I thought I'd also share my