Dealing with multiple users on a single box can be frustrating at first. Especially when they edit the same files. I wanted to create a sort of hierarchy of users with my root and personal accounts at the top, and a pool of sub-accounts below. Here’s how I solved thisproblem in Ubuntu:
First, create a common group:
groupadd <group-name>
Next, make sure all of the sub-accounts use the new group as its default account.
For new users:
useradd -G<group-name><username>
For existing users:
usermod -a-G<group-name><username>
When a user creates a file or directory, they normally would use their own group. What we want is that any account in the common group to use the new group as its default:
usermod -g<group-name><username>
Last, change the sub-users’ default umask settings so that it treats its own settings exactly the same as the group settings. Make sure to only run this command as one of the sub-accounts:
umask 0002
Now you have a list of accounts with limited permissions that your main account will always have access to. Now this is not an optimal, and probably secure solution, but since this only for my development environment, its good enough.
I’ve always been a big fan of VSTreeExplorer since I started using Vim. Recently, I came across NerdTree, which is a much better alternative. It really makes it much easier to manage multiple tabs and sessions and has many more keybindings and mouse interactions making it the closest to the Visual Studios experience in Vim. Here’s a really good animated gif with a basic tutorial on its use:
If you haven’t heard about Ubiquity, I advise you to check it out. It’s a great Firefox plugin that allows basically any service to be at your disposal. The basic premise is you highlight some words, start typing an action, and it will find a service that meets your needs. Check out the video below for a better explanation. Watch out for a Grooveshark command later on.
I decided for my first 2 entries into the Netflix prize, I would see just how good/bad current scores are. For those who have never heard of the Netflix prize, see my post here.
First, I will predict a 3 for every rating just to see how much deviation there really is from that average ranking. And for my second submission, I just use a random number between 1 and 5 to see how well a random prediction fares with the rest of the leaderboard. After setting those two scripts up and submitting, I never got back a score. I’m not that dissappointed but maybe they saw that i was just sending them random/constant data and decided I was not worth their time. Made me feel kinda sad…
Also, I was having some difficulties initially writing my script in python, so I decided to just hurry up and do it in PHP and then port it python later. The first thing i noticed between the two scripts was just how much faster python is than php. I ran each script three times and calculated the averages. Below are the results:
Language
Script
Time
Python
Constant
30.037 seconds
PHP
Constant
40.388 seconds
Python
Random
9.312 seconds
PHP
Random
19.464 seconds
I know I’m probably beating a dead horse here but python is WAY faster. And nothing really intensive or complex is going on here: string concatenation, random number generation, and writing to a file. That is it. Python performs the constant value prediction ~50% faster and the random value prediction ~25% faster.
As I get more comfortable with python and its vast library of scripts, it will definitely become my goto scripting language. For all you Ruby enthusiasts, especially you, Travis, the ruby language is very well thought out, but until anybody can come close to NumPy/SciPy, I will stick to python for now.
I decided a couple of nights ago to see how well I would do in the Netflix Prize. This is a competition from the company Netflix, an online movie rental site, that gives two gigs worth of user ranking data to see if anyone can improve their own ranking algorithm, Cinematech, by at least 10%. Many have tried, but few have come close.
Recommendations are a fairly difficult problem. At Grooveshark, we have our own recommendation system using various statistical techniques that have been fine-tuned over the years. They are not perfect, but they do come close to what Pandora, and Last.fm have to offer in certain instances. I’m sure the techniques Grooveshark uses are no way near as sophisticated as Google or Amazon, but we try our best. Early Google has shown that simple algorithms using the right data can be more successful than advanced statistical tools. But even with Google, their algorithms and tools have grown more sophisticated over time. In my opinion, simple tools using the correct insights can be very powerful as proven by a psychologist who has jumped very high in the leaderboard (Just a guy in a garage).
Overall, this project gives a lot of goodwill to Netflix for being so open and providing a great competition for researchers and joe-schmoes alike. I really just want to apply some of the new techniques I have learned in an environment other than music (not surprising when you spend 60 hours a week thinking about music). Here’s some of the books I have read or currently reading:
Along with these books, I have kept up a large collection of recommendation and music information retrieval papers. I have read a lot of them, but most of them are on my to-read list. If you would like, check out my document subversion repository at: svn://cmunezero.com/docs.
Code editors are among the most important applications for a programmers. They are also the source of some the most heated debates online. Whether you use a full-fledged IDE like Eclipse or VisualStudios, or even a souped up text editors like Emacs or Vim, everybody has a favorite. My first IDE was Borland Turbo C and after a couple of months, “purchased” a free copy of VisualC++ (later known as VisualStudios). Finally paid for a student version when my parents found out I was really interested in programing.
VisualStudios was my main IDE until I started web development and moved to Linux. For more than a year now, I’ve been using Eclipse because their plugin system has enabled people to create really good editors for Java, PHP, Javascipt, Flex and HTML/CSS. Because it’s all in one program, the editor is really heavy and fairly bug prone. Recently, I’ve been making the switch from using Eclipse exclusively to moving most of my development to Vim.
Vim is a very good text editor and I chose it ahead of Emacs because in my opinion, the commands are simpler. Most of the common functionality of Eclipse can be found in Vim: search/replace, syntax highlighting, XDebug-ing, and much more. The debate between gui editors or vim/emacs is basically a moot point. They are just tools. Certain people’s thinking patterns are just more suited to one tool than the other. Since I use the command line for almost everything I do, using vim allows a much easier transition between editing files, writing scripts and interacting with remote hosts. For me, vim, along with all of the standard linux apps (find, grep, tail, ssh, scp, etc…), allows me to work more efficiently than any other tool so that is what I use.
If you installed Memcached using Yum under the RedHat flavor of Linux, they have this really nice init.d scripts for starting and stopping Memcache. I modified it in order to support creating a bunch memcache instances using contiguous ports. What’s great is that only the “start” script has to be modified since the “stop” script uses a special RedHat function, killproc, which can accept a program name or path and kill all instances of that program. I’m still a noob at bash scripts but here is my only changes:
NUMBUCKETS=3#only new value needed
start(){for((i=1;i<=$NUMBUCKETS;i+=1)); doFULLPORT=${PORT}${i}echo-n $"Starting $FULLPORT ($prog): \n"
daemon $prog-d-p$FULLPORT-u$USER-c$MAXCONN-m$CACHESIZE$OPTIONSRETVAL=$?doneecho[$RETVAL-eq0]&&touch/var/lock/subsys/$progreturn$RETVAL}
Since switching to Linux, I have slowly fallen in love with Vim. I love how Vim makes it so that “your hands should never have to leave your keyboard” (Chris). The biggest drawback to using Vim, and Emacs, is that there’s a fairly steep learning curve. You pretty much have to abandon your comfort zone and force yourself to learn all of the different key bindings.
I’m very lucky in that I work with two vim gurus: Chris and Travis. Basically any question I have ever had with Vim, these two were able to answer them. But for times when they are not around I love using these sites:
This is a very short list because Vim is based on a few basic concepts and building on top of that. Once you get the basics, learning how to use buffers and macros gives you the ability to edit your files in any manner.
I recently read a Wired article where people achieved success losing weight because Weight Watchers is basically an RPG. One game/exercise that I often do is to see how many lines of code or components I can write without any errors. It’s hard to quantify but my record so far as about 200 lines of Javascript/AJAX code. It was kind of cheating because I was basically re-using Javascript and backend PHP code that had been thoroughly tested. Overall, this is a pretty good method to increase the amount of code you can hold in your head and attempts to reduce the relying of debugging tools in favor of self/mental debugging.
So a brand new version of Sphinx has come out. I’ve been using a beta version of 0.9.8 so I’ve been using most of the new features already but the list of new features and bug fixes is still pretty impressive. For those of you who don’t know, Sphinx is a MySQL full-text replacement for implementing search. And its hella fast.
