Dan Luu danluu

## introrx.md

      
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                staltz
                / introrx.md
            
            
              Last active
              May 7, 2024 09:38
            
              
                The introduction to Reactive Programming you've been missing
              
          
    The introduction to Reactive Programming you've been missing

(by @andrestaltz)

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.


## index.html
<html>
	<head>
		<title>Simple Line Graph using SVG and d3.js</title>
		<script src="http://mbostock.github.com/d3/d3.v2.js"></script>
		<style>
			/* tell the SVG path to be a thin blue line without any area fill */
			path {
				stroke: steelblue;
				stroke-width: 1;
				fill: none;

## diskchecker.pl
#!/usr/bin/perl
#
# Brad's el-ghetto do-our-storage-stacks-lie?-script
#

sub usage {
    die <<'END';
Usage: diskchecker.pl -s <server[:port]> verify <file>
       diskchecker.pl -s <server[:port]> create <file> <size_in_MB>
       diskchecker.pl -l [port]

## Dockerfile.tmpl
# using VirtualBox version $VBOX_VERSION

FROM boot2docker/boot2docker
RUN apt-get install p7zip-full

RUN mkdir -p /vboxguest && \
    cd /vboxguest && \
    curl -L -o vboxguest.iso http://download.virtualbox.org/virtualbox/$VBOX_VERSION/VBoxGuestAdditions_$VBOX_VERSION.iso && \
    7z x vboxguest.iso -ir'!VBoxLinuxAdditions.run' && \
    sh VBoxLinuxAdditions.run --noexec --target . && \

## ahi.md

      
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                zmagg
                / ahi.md
            
            
              Last active
              November 16, 2019 08:24
            
              
                adaptive hash index in mysql
              
          
    omg julia,
Today I learned something about the buffer pool in MySQL that made it seem less like performance black magic! So, before today I knew that the buffer pool was an in-memory cache for MySQL that let you do super fast lookups (especially PK lookups, but maybe only PK lookups (? uncertain on that one)), like, our PK lookups with the BP turned on take microseconds, and they did so even before we moved to SSDs for all our databases [1]. I didn't know ANYTHING about how the buffer pool worked though, other than like, "caching: it makes things faster".
So, today we were doing a routine schema change truncating some old tables. We did a TRUNCATE operations live with all the databases still in configuration serving live traffic [2], because a TRUNCATE essentially does a DROP/CREATE at the table level, instead of row by row (since MySQL 5.1, we're on 5.5), so it's usually reasonably high performance. TURNS OUT, it also does some really not-so-performant cache invalidation on the buffer pool! This

  
## tmux libevent
NOTE: I am using bash for this.

NOTE2: Another approach for getting tmux would be to use gentoo-prefix or netbsd's pkgsrc. I
didn't have too much luck with gentoo-prefix. NetBSD was pretty straight forward but it had
an old version of tmux (1.1).

Here is how to get tmux compiled if you can get your systadmins to installed it ... or
any other weird reason. I assume you have some basic libraries and headers installed (like
ncurses, etc...). If not, you'll have to compile those ones too.

## debugging.md

      
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              4 comments
            
          
              12 stars
            
          
                staticfloat
                / debugging.md
            
            
              Last active
              February 24, 2017 03:11
            
              
                Julia Debugging Procedures
              
          
    Julia Debugging Procedures

So you managed to break Julia.  Congratulations!  Collected here are some general procedures you can undergo for common symptoms encountered when something goes awry.  Including the information from these debugging steps can greatly help the maintainers when tracking down a segfault or trying to figure out why your script is running slower than expected.
If you've been directed to this page, find the symptom that best matches what you're experiencing and follow the instructions to generate the debugging information requested.  Table of symptoms:


Segfaults during bootstrap (sysimg.jl)


Segfaults when running a script


## bench.c
#include <stdint.h>
#include <stddef.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
uint64_t builtin_popcnt(const uint64_t* buf, size_t len){
  uint64_t cnt = 0;
  for(size_t i = 0; i < len; ++i){
    cnt += __builtin_popcountll(buf[i]);
  }

## Thompson-exercises.md

      
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                darius
                / Thompson-exercises.md
            
            
              Last active
              December 18, 2015 20:49
            
          
    (Superseded by https://github.com/darius/regexercise )

Some coding exercises, working up to matching regular expressions with Thompson's algorithm.
I'm assuming you know what a regular expression is and you're a fairly
experienced programmer. I don't know if these exercises are either fun or
effective -- please comment or fork here or email withal@gmail.com to help me
improve them.
The problems


## gist:5621682
// On my system:
//   virtual call time: 4.340
//   non-virtual call time: 3.970
//   virtual call overhead 9.32%

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

#define NOINLINE __attribute__ ((noinline))
	<html>
	<head>
	<title>Simple Line Graph using SVG and d3.js</title>
	<script src="http://mbostock.github.com/d3/d3.v2.js"></script>
	<style>
	/* tell the SVG path to be a thin blue line without any area fill */
	path {
	stroke: steelblue;
	stroke-width: 1;
	fill: none;
	#!/usr/bin/perl
	#
	# Brad's el-ghetto do-our-storage-stacks-lie?-script
	#

	sub usage {
	die <<'END';
	Usage: diskchecker.pl -s <server[:port]> verify <file>
	diskchecker.pl -s <server[:port]> create <file> <size_in_MB>
	diskchecker.pl -l [port]
	# using VirtualBox version $VBOX_VERSION

	FROM boot2docker/boot2docker
	RUN apt-get install p7zip-full

	RUN mkdir -p /vboxguest && \
	cd /vboxguest && \
	curl -L -o vboxguest.iso http://download.virtualbox.org/virtualbox/$VBOX_VERSION/VBoxGuestAdditions_$VBOX_VERSION.iso && \
	7z x vboxguest.iso -ir'!VBoxLinuxAdditions.run' && \
	sh VBoxLinuxAdditions.run --noexec --target . && \
	NOTE: I am using bash for this.

	NOTE2: Another approach for getting tmux would be to use gentoo-prefix or netbsd's pkgsrc. I
	didn't have too much luck with gentoo-prefix. NetBSD was pretty straight forward but it had
	an old version of tmux (1.1).

	Here is how to get tmux compiled if you can get your systadmins to installed it ... or
	any other weird reason. I assume you have some basic libraries and headers installed (like
	ncurses, etc...). If not, you'll have to compile those ones too.
	#include <stdint.h>
	#include <stddef.h>
	#include <time.h>
	#include <stdio.h>
	#include <stdlib.h>
	uint64_t builtin_popcnt(const uint64_t* buf, size_t len){
	uint64_t cnt = 0;
	for(size_t i = 0; i < len; ++i){
	cnt += __builtin_popcountll(buf[i]);
	}
	// On my system:
	// virtual call time: 4.340
	// non-virtual call time: 3.970
	// virtual call overhead 9.32%

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

	#define NOINLINE __attribute__ ((noinline))