2012-03-02 - updated to use ruby 1.9.3 and official instead of system rvm.

When trying to install ruby 1.9.2 using rvm I got a nasty suprise:

ossl_ssl.c:110:1: error: ‘SSLv2_method’ undeclared here (not in a function)
ossl_ssl.c:111:1: error: ‘SSLv2_server_method’ undeclared here (not in a function)
ossl_ssl.c:112:1: error: ‘SSLv2_client_method’ undeclared here (not in a function)
make[1]: *** [ossl_ssl.o] Error 1
make[1]: Leaving directory `/var/cache/ruby-rvm/src/ruby-1.9.2-p180/ext/openssl'
make: *** [mkmain.sh] Error 1

The solution

# install rvm
bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer )
# make sure we have $rvm_path
source /etc/profile
# don't use ubuntus openssl
rvm pkg install openssl
rvm install 1.9.3-p125 --with-openssl-dir=$rvm_path/usr

I generally like dynamic languages and in generally don't run into much trouble with them. Having that said, I hate the way undefined and NaN work in Javascript.

This turns a simple typo into a NaN apocalypse. After half of your numbers have turned into NaNs it's hard to find out where they came from.

var o = {y: 0},
#NaN
1/o;
#NaN
var x = 1/o.x;
#NaN
var y = x*10;

Setting up traps

So how do you catch stray NaNs? You set up traps. Because it can become very tedious and error prone to have asserts everywhere I wrote a little helper, fuckNaN().

function fuckNaN(obj, name){
    var key = '__' + name;
    obj.__defineGetter__(name, function(){
        return this[key];
    });
    obj.__defineSetter__(name, function(v) {
        // you can also check for isFinite() in here if you'd like to
        if(typeof v !== 'number' || isNaN(v)){
            throw new TypeError(name + ' isNaN');
        }
        this[key] = v;
    });
}

// Examples
var o = {x: 0};
fuckNaN(o, 'x');
// throws TypeError: x isNaN
o.x = 1/undefined;

// Also works with prototypes
function O(){
    this.x = 0;
}
fuckNaN(O.prototype, 'x');
var o = new O();

// throws TypeError: x isNaN
o.x = 1/undefined;

Place some of those traps during debug mode in critical locations like your Vector and Matrix classes and they will bring doom and destruction to those NaNs..

Note: This doesn't work in IE<=8 and you shouldn't use it in production. Use it as a tool during development to make your code fail early.

I got myself a new toy - a Thinkpad X1. I wasn't really sure whether I should get the X1 or a Macbook Air. The main reason I decided to get the Thinkpad is because I prefer Linux for coding and I actually prefer the style of the hardware. It looks like a hackers tool and not like a shiny fashion accessory, but that's of course just my taste. It's also a lot more powerful in terms of CPU and connectivity (RJ45 jack, HDMI out, USB3, built in 3G modem). The downside is the display, the IPS displays Apple uses are just SO much better. But hey, I'm a developer not a designer.

This post describes the tweaks I did to make this notebook even better. They are also a documentation for myself. It targets advanced users.

TL;DR

Everything works out of the box, but a few tweaks make it way more awesome.

Thinkfan

The default fan settings are very aggressive and result in a lot of noise. I use thinkfan for manual fan control. This reduces the noise significantly.

#/etc/thinkfan.conf
sensor /sys/devices/platform/coretemp.0/temp1_input
sensor /sys/devices/platform/coretemp.0/temp2_input
sensor /sys/devices/platform/coretemp.0/temp3_input
sensor /sys/devices/virtual/hwmon/hwmon0/temp1_input

(0,	0,	60)
(1,	60,	70)
#(2,	76,	61)
#(3,	52,	63)
#(4,	56,	65)
#(5,	59,	66)
(7,	70,	32767)

Note that those are pretty extreme settings, use with caution and don't blame me.

Reducing power consumption

In order to improve battery life and to keep the device cool I tweaked some settings and disabled all unused devices in the bios. The changes save almost 10 watt!

#/etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.i915_enable_rc6=1"
# run update-grub after change

#/etc/rc.local
echo 1500 > /proc/sys/vm/dirty_writeback_centisecs
for i in /sys/bus/usb/devices/*/power/autosuspend; do echo 1 > $i; done
echo min_power > /sys/class/scsi_host/host0/link_power_management_policy
echo min_power > /sys/class/scsi_host/host1/link_power_management_policy

Also you should consider using flashblock for firefox/chrome. Flash will drain your battery. If you don't believe it just look at the cpu wakeups it creates using powertop.

SSD TRIMing

I use an Intel SSD in the Notebook. The installation was a bit fiddly but the performance is just incredible. The thing boots in seconds. In order to get TRIM support I added discard to the partition options in /etc/fstab.

#/etc/fstab
UUID=b38561bd-9ca9-44a6-848d-ec90f31e1955 /               ext4    discard,errors=remount-ro 0       1

Wireless

802.11N seemed to create problems with my WLAN so I disabled it.

#/etc/modprobe.d/_wlan.conf 
options iwlagn 11n_disable=1

HDAPS

HDAPS offers you access to the accelerometer and advanced battery functions. It's simple to install:

sudo apt-get install tp-smapi-dkms
sudo modprobe -a tp_smapi hdaps
# get battery details
grep -r . /sys/devices/platform/smapi/BAT0/
# load on boot
echo "tp_smapi" >> /etc/modules
echo "hdaps" >> /etc/modules

Conclusion

With all those tweaks done the Thinkpad X1 becomes a durable, light, quiet and fast notebook with a lousy screen.

29a.ch/sandbox/2011/addresscloud/

As some of you know I work for local.ch. I was looking for cool visualizations to do with our data for quite a while, missing the obvious - plotting all our 3.7 million geocoded addresses in 3D using WebGL! I'm actually quite impressed by the accuracy of the data. But go and have a look for your self.

Controls

WASD + Mouse (drag). Velocity is scaled with altitude.

Video

If you can't see the demo for some reason I uploaded a short video of the demo to youtube.

Techniques

The points are encoded in a Float32Array, then sorted and gziped using a python script. Sorting the data improves the compression ratio by over 200% so it's well worth the effort. This brings the original 100mb file down to 7mb.

The file is then loaded using XHR level 2, which supports binary files and progress events. The points are then rendered using WebGL as GL_POINTS and additive blending is used to give it a glow effect. In the future I might add HDR rendering and blooming.

There is no level of detail or culling performed so this will require a relatively powerful rig. Also note that for some reason Firefox Aurora (9) seems to be quicker than Chrome Dev (16) for some mysterious reason. I would expect all of the work to be done by OpenGL so I'm not sure about where this comes from. It could be chromes process isolation.

Sourcecode

You can find the source code on github if you want to get into some hacking. Note that the data belongs to local.ch and may not be used.

View Demo

Some of you might remember my Chaotic Particles demo from last year. That demo was featuring 10'000 particles on a plain old 2d canvas. I decided to optimize that demo a bit in order to support 100'000 particles. I also fixed a little issue where numeric inaccuracy allowed particles to escape and made the influence map more fine grained.

Want to see the source? Just use view source and feel free to ask questions.

Next up: 4'000'000 Particles using WebGL.