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

gunjanpatel

Revert the full commit

Sometimes you may want to undo a whole commit with all changes. Instead of going through all the changes manually, you can simply tell git to revert a commit, which does not even have to be the last one. Reverting a commit means to create a new commit that undoes all changes that were made in the bad commit. Just like above, the bad commit remains there, but it no longer affects the the current master and any future commits on top of it.

git revert {commit_id}

About History Rewriting

Delete the last commit

Deleting the last commit is the easiest case. Let's say we have a remote origin with branch master that currently points to commit dd61ab32. We want to remove the top commit. Translated to git terminology, we want to force the master branch of the origin remote repository to the parent of dd61ab32:

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.

peschee

Sometimes, we have to access git repositories over SSL and the server only provides a self-signed certificate 🙈. Although there are ways to increase the trust level for the self-signed certificate (https://confluence.atlassian.com/fishkb/unable-to-clone-git-repository-due-to-self-signed-certificate-376838977.html, https://confluence.atlassian.com/bitbucketserverkb/resolving-ssl-self-signed-certificate-errors-806029899.html), my recommendation is to just ignore SSL verification alltogether.

Prepend GIT_SSL_NO_VERIFY=true before every git command run to skip SSL verification. This is particularly useful if you haven't checked out the repository yet.

Run git config http.sslVerify false to disable SSL verification if you're working with a checked out repository already.

MattPD

Program Analysis Resources

(draft; work in progress)

See also:

• Compilers
  • correctness
• Program analysis:
• Dynamic analysis - instrumentation, translation, sanitizers

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.

vindarel

Testimonies

CL's compiler

The thing in CL I miss most doing Clojure as my day job? CL's compiler. I like having a compiler tell me at compile time about the mistakes I've made. Bogus arguments. Unreachable code because of unhandled exceptions, and so on. CL saves me round after round of bugs that in clojure aren't found until you run the code. If you test well, it's found when testing, if you don't it's found in production. "Clojure compiler" almost demands air quotes.

CL's optional but oh-so-useful model of type declarations is also infinitely more useful (to me) than Clojure's use of "spec", and instrumentation that happens only at test time because of the cost. Depending on the OPTIMIZE declarations, other type defs are a floor wax and dessert topping. Want checks for argument types? Lower optimizations. Want most efficient machine code? High optimizations.

/u/Decweb, March 2023 https://www.reddit.com/r/lisp/comments/11ttnxk/the_rise_fall_of_lisp_too_good_for_the_rest_of/jczpysp/

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

gatlin

#!/bin/bash

# source: http://www.haskell.org/pipermail/haskell-cafe/2011-March/090170.html

sudo rm -rf /Library/Frameworks/GHC.framework
sudo rm -rf /Library/Frameworks/HaskellPlatform.framework
sudo rm -rf /Library/Haskell
rm -rf ~/.cabal
rm -rf ~/.ghc
rm -rf ~/Library/Haskell

justintv

# If you work with git, you've probably had that nagging sensation of not knowing what branch you are on. Worry no longer!

export PS1="\\w:\$(git branch 2>/dev/null | grep '^*' | colrm 1 2)\$ "

# This will change your prompt to display not only your working directory but also your current git branch, if you have one. Pretty nifty!

# ~/code/web:beta_directory$ git checkout master
# Switched to branch "master"
# ~/code/web:master$ git checkout beta_directory
# Switched to branch "beta_directory"