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

chaitanyagupta

Reader Macros in Common Lisp

This post also appears on lisper.in.

Reader macros are perhaps not as famous as ordinary macros. While macros are a great way to create your own DSL, reader macros provide even greater flexibility by allowing you to create entirely new syntax on top of Lisp.

Paul Graham explains them very well in [On Lisp][] (Chapter 17, Read-Macros):

The three big moments in a Lisp expression's life are read-time, compile-time, and runtime. Functions are in control at runtime. Macros give us a chance to perform transformations on programs at compile-time. ...read-macros... do their work at read-time.

troyfontaine

Methods of Signing Git Commits on MacOS

Last updated March 13, 2024

This Gist explains how to sign commits using gpg in a step-by-step fashion. Previously, krypt.co was heavily mentioned, but I've only recently learned they were acquired by Akamai and no longer update their previous free products. Those mentions have been removed.

Additionally, 1Password now supports signing Git commits with SSH keys and makes it pretty easy-plus you can easily configure Git Tower to use it for both signing and ssh.

For using a GUI-based GIT tool such as Tower or Github Desktop, follow the steps here for signing your commits with GPG.

lfender6445

Pry Cheat Sheet

• Youtube Tutorial 2013

Command Line

• pry -r ./config/app_init_file.rb - load your app into a pry session (look at the file loaded by config.ru)
• pry -r ./config/environment.rb - load your rails into a pry session

Debugger

william8th

# Set the control character to Ctrl+Spacebar (instead of Ctrl+B)
set -g prefix C-space
unbind-key C-b
bind-key C-space send-prefix

# Set new panes to open in current directory
bind c new-window -c "#{pane_current_path}"
bind '"' split-window -c "#{pane_current_path}"
bind % split-window -h -c "#{pane_current_path}"

halgari

So you’d like to contribute to Clojure, great! Let’s talk about what that involves.

The first thing you’ll want to make sure is that your idea is valid, and that you won’t spend a ton of time working on something that won’t make into master. To do this, you should create a JIRA ticket. For example, let’s say we want to improve how core.async handles channel closing propagation. It’s not a super complex problem, but there are some design questions about which of the various semantics currently in place should be the default, and if some semantics should be configurable.

So start by making a JIRA ticket and stating what the problem is you’re trying to solve, what the possible options for solving the problem. Now hit save and wait for the ticket to be triaged. Alex Miller will take a look when he can, and that can take a few days to a few weeks, depending on the time of the year (he has other responsibilities). Alex may out-right reject the idea if he knows Rich would never approve the ticket, but otherwise h

Beneboe

How to Setup Verified Commits

Quick guide on how to setup git signing. Information is aggregated from following sources:

• https://help.github.com/articles/signing-commits/
• https://help.github.com/articles/telling-git-about-your-signing-key/
• https://help.github.com/articles/generating-a-new-gpg-key/

georgiana-gligor

Create PDF files from Markdown sources in OSX

When [Markdown][markdown] appeared more than 10 years ago, it aimed to make it easier to express ideas in an easy-to-write plain text format. It offers a simple syntax that takes the writer focus away from the formatting, thus giving her time to focus on the actual content.

The market abunds of editors to be used for help with markdown. After a few attempts, I settled to Sublime and its browser preview plugin, which work great for me and have a small memory footprint to accomplish that. To pass the results around to other people, less technical, a markdown file and a bunch of images is not the best approach, so converting it to a more robust format like PDF seems like a much better choice.

[Pandoc][pandoc] is the swiss-army knife of converting documents between various formats. While being able to deal with heavy-weight formats like docx and epub, we will need it for the more lightweight markdown. To be able to generate PDF files, we need LaTeX. On OSX, the s

mort3za

# Generate a new pgp key: (better to use gpg2 instead of gpg in all below commands)
gpg --gen-key
# maybe you need some random work in your OS to generate a key. so run this command: `find ./* /home/username -type d | xargs grep some_random_string > /dev/null`

# check current keys:
gpg --list-secret-keys --keyid-format LONG

# See your gpg public key:
gpg --armor --export YOUR_KEY_ID
# YOUR_KEY_ID is the hash in front of `sec` in previous command. (for example sec 4096R/234FAA343232333 => key id is: 234FAA343232333)

rvl

Pushing to Multiple Git Repos

If a project has to have multiple git repos (e.g. Bitbucket and Github) then it's better that they remain in sync.

Usually this would involve pushing each branch to each repo in turn, but actually Git allows pushing to multiple repos in one go.

If in doubt about what git is doing when you run these commands, just