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

rcoup

#!/bin/bash
set -e

# Usage:
#   rsync_parallel.sh [--parallel=N] [rsync args...]
# 
# Options:
#   --parallel=N	Use N parallel processes for transfer. Defaults to 10.
#
# Notes:

msg555

#include <stdio.h>
#include <stdlib.h>

#define STACK_SIZE (1 << 26)
#define STACK_PAD 128

int rec(int n) {
  return n == 0 ? 0 : rec(n - 1) + 1;
}

isnowfy

# Example usage
# $ python dft.py | gnuplot
# 9
# 0 0
# 1 1
# 2 2
# 0 2
# 1 1
# -1 1
# 0 2

aras-p

// Just before switching jobs:
// Add one of these.
// Preferably into the same commit where you do a large merge.
//
// This started as a tweet with a joke of "C++ pro-tip: #define private public",
// and then it quickly escalated into more and more evil suggestions.
// I've tried to capture interesting suggestions here.
//
// Contributors: @r2d2rigo, @joeldevahl, @msinilo, @_Humus_,
// @YuriyODonnell, @rygorous, @cmuratori, @mike_acton, @grumpygiant,

xf1

 Remuxing

Why Remux Blu-rays?
-You use MPC-HC (or similar DShow players) and standard filters for playback. You can also use better quality renderers like Haali, EVR and madVR.
-You get the ease of playback of a re-encode without the quality loss. A double click off the .mkv will start the movie - no annoying warnings, loading screens, previews and setup menus.
-You don't have to deal with horribly bloated, unstable and expensive PowerDVD or Arcsoft playback software.
-You don't have to mess with ISO creation, correct BD folder structure, UDF and SPTD drivers, and image mounting every time you want to watch a movie.
-You never have to worry about the region code setting of a disc.
-You never have to worry about HDCP or PAP content protection.
-You never have to worry about your software player downsampling your audio - get full bit-depth and frequency resolution, 24bit/96kHz or higher, not 16/48.

patriciogonzalezvivo

Trigonometry

const float PI = 3.1415926535897932384626433832795;
const float PI_2 = 1.57079632679489661923;
const float PI_4 = 0.785398163397448309616;

float PHI = (1.0+sqrtf(5.0))/2.0;

akorn

#!/bin/zsh
#
# Copyright (c) 2014, 2020 by Dr. András Korn. Implements the basic idea of a similar script by Robert Coup (2013).
# License: GPLv3

function usage() {
	echo 'Usage:

rsync_parallel [--parallel=N] <args to find(1) to generate list of stuff to transfer> -- <args to rsync>
 

patrickt

A Quick and Dirty Lens primer

Why does Lens exist? Well, Haskell records suck, for a number of reasons. I will enumerate them using this sample record.

data User = User { login    :: Text
                 , password :: ByteString
                 , email    :: Text
                 , created  :: UTCTime
 }