Alejandro Erickson
Senior Software Developer at Copperleaf Technologies

Do you collect anything?  Maybe you collect beach stones or shells, or maybe it’s imported beer cans.  Or maybe your collectors items can be found in hobby shops or car dealerships.  Whatever it is, think about the reasons for maintaining this collection.  What are the benefits, what the challenges?  Better yet, maybe you have no collections and you are wondering why other people bother with them.

I have a somewhat unusual collection and would like to share a piece of it with you.  The items in it can be found nearly everywhere, yet they are rare enough that I find only about two to three per year.  When I do find one I am verging on elation.  I find myself mid conversation with someone, either walking or driving down the street and I see one out of the corner of my eye.  I squeak, yelp or make a similarly ridiculous exclamation and run over to pick it up.  After inspecting it briefly I hold it up in the air triumphantly.  Struggling through their perplexity, my conversation partner will ask, “Why would you want that?”. 

“It’s for my collection, isn’t it cute!?!”

“Yeah, it is kinda… that’s a weird collection, how many do you have?”

“Ten or fifteen…  I’ve been collecting them since I was about 15.”

“Why would you collect that?”, they ask.  Thus I have had to justify the effort spent on this frivolous activity and hence the story you are reading now. 

I’ll begin by explaining why it is fun to collect things and second, what

makes a good collection.

Humans, being social animals, do many things for social reasons and I think that collections are no exceptions.  They are great conversation topics, allowing the collector to show off different pieces, and telling their stories.  The visitor gets to know the collector this way and can express their feelings about the collections, thus reciprocating.  It doesn’t take a psychologist to realize that devices which help us find common ground with others can be very useful to our social lives.

We should also consider, however, the joy brought to the collector.  There are three aspects that make collections enjoyable in this respect.  The Hunt, The Find and The Story.  I will let these first two speak for themselves.  As for The Story, recall the last time you worked for something and were proud of the result.  For example, you might have taken a creative photograph or cooked a meal for a special occasion.  Let me burst your bubble for a moment, by saying, chances are it was not very good on a world scale.  You probably enjoyed it, however, because of the story behind it.  In the case of a collection, each item tells the story of The Hunt and The Find.  Each time you see or use an item, you are reminded of its story.

There are a few criteria for a collection to bring the enjoyment I have talked about, especially for people who have less money, space or time.

1.  The Hunt should be challenging, but not take over your life.  The effort put into finding each item adds to The Story, so things you can easily buy from a store at any time are not ideal.  There are good collections that you need to buy, but often they involve rare items or things only sold abroad.  In my opinion that waiting until a company produces certain collector’s items is not a good Hunt.  It usually just makes the collector look like a sucker.

On the other hand, things like trading cards consume more energy than they may be worth.  The key reason for my dislike of these and official collectors item product lines is that the collection is completed before it begins.  Instead of discovering new items, the collector is simply trying to obtain all of the existing ones.  Instead of being excited by what you might find, you are motivated by specific things that you do not have.  I call these Consumer Collections and they should usually be avoided because they become an unpleasant fixation.

2.  In most cases, The Find is a momentary thing.  You may want to consider  that it may be fun to find an item in the company of a friend.  If they are only found when you are alone, you will miss out on this.  Sometimes The Find is a longer process, especially for large or expensive items.  It is my preference that The Find be simple and may occur anywhere so that it can  be a spontaneous thing to share with a friend.

3.  Of the three, The Story carries the most weight.  If your collection brings you unequaled joy and conversation time and again then it is likely a good collection.  The Story is not independent, however, because The Hunt and The Find tell much of The Story.

To summarize, a good collection consists of an enjoyable Hunt, and exciting

Find and a Story you have an emotional connection to.  Better yet, The Story’s connection might extend to your friends.

Without further ado, here is a photo of my latest piece, found at Broadway and Ash in Vancouver on July 5th, 2010.  I was crossing the street with my mom when I spotted the flamboyant pink water shoe in the crosswalk.  “Shoe!” I cried inwardly, and ran to pick it up, bringing it back to show my mom.  Having not found any recently, I was reminded that Found Baby Shoes make a wonderful collection, satisfying all of the above.  On top of being fun to keep an eye out for and a surprise every time, they are small, somewhat rare and totally free!

There is no question that it is an odd thing to collect, but this only adds to the amusement when my friends ask me why I have them.  It’s a fun moment in conversation and the perfect opportunity to preach my collection philosophy :)

I would love to hear about your own oddball collections in the comments below!

Lastly, if you find a baby shoe and want to send it to me I would be very happy to add it to the collection, so please contact me.  I do not collect pairs of shoes, nor do I collect shoes that were not at one point lost and later found.

This is a flash app that I made for my advisor, Frank Ruskey and his former student, Aaron Williams, for their presentation of The Feline Josephus Problem at the FUN With Algorithms Conference 2010, Ischia Island, Italy.

From Wikipedia, the history of the original Josephus Problem is the following:

The problem is named after Flavius Josephus, a Jewish historian living in the 1st century. According to Josephus’ account of the siege of Yodfat, he and his 40 comrade soldiers were trapped in a cave, the exit of which is blocked by Romans. They chose suicide over capture and decided that they would form a circle and start killing themselves using a step of three. Josephus states that by luck or maybe by the hand of God (modern scholars point out that Josephus was a well educated scholar and predicted the outcome), he and another man remained the last and gave up to the Romans.

The two parameters in the above problem are the number of soldiers and the “step” size.  That is, instead of killing every third person left in the circle, every kth one is killed.  In the Ruskey-Williams variation the soldiers have the super powers of cats and may have more than one life.  The parameters of the problem are (n,k,l).  These are for the number of soldiers, the skip count and the number of lives.  The original problem is (40,3,1).

Ruskey and Williams published a paper on this.  Among their findings was that, rather curiously, the surviving soldier is always the same if the soldiers have a number of lives greater than the nth fibonacci number.  Even more interestingly, if you fix the number of soldiers n and you declare the survivor before beginning, you can find a skip count k that allows this to happen for any number of lives l.  What’s more, is that the same skip count k works for all values of l!  How cool is that! :D.

Much of the paper is very accessible and would be a great read for undergraduate computer science or math students and fun for the rest of us too :).  It can be found on Frank Ruskey’s webpage at this link.

I often get ahead of myself and I’m going to do it here.  With no introduction to tatami tilings nor to tomography and not to mention, their intersection, I present this flash application.

I appreciate your comments and bug reports (post them here if you like).  Apologies for the jumbled user interface, I’ll update that stuff if and when I realize that someone other than me and a couple of friends want to play with it.

Try the following:  Press “Random Tiling” and then press “Tomography”.  Read the instructions that appear at the bottom right and see how fast you can place all the mats onto the grid.  Note that 1x1 mats appear twice (you’ll see why when you place one).

Without further ado:


A few months back, I promised myself that once I got a real tamper (see my previous video), I would be ready to make a new coffee video.  Last week I visited Reg Barber at his shop in Central Saanich, BC, Canada, and he cut a 51mm C-Flat tamper for my Pavoni Professional machine (I severely regret not video taping him doing it), so here I am, delivering on my promise.

As you probably know, the learning curve for a lever machine is quite long.  I have had my Pavoni Pro for over a year now and it has only been in the last few months that I’ve really begun to understand how to use it.  My experience when I bought it was that although there were Pavoni videos out there, but not enough of them were made by experienced owners.  There were some good written resources, however, such as and this video was helpful (though the guy talks a lot and over complicates things).  I hope I understand this machine well enough now to make a useful contribution!

I pull a shot of espresso into a clear shot glass.  I use a Rancilio Rocky grinder and the coffee is the Causeway Blend from Caffe Fantastico.  The music I used is performed by a Chilean group called Los Melódicos: Orlando Patiño, Jorge Segura, Leoncio Hidalgo.  I hope they appreciate the exposure.

A couple more notes on extraction time.  As you can see, that was a 35 second shot, but the first lifting would have been about 20-25 seconds.  I have not been able to lift the lever twice and stay within the right amount of time, and I am beginning to think that the machine was not designed for that.  I can estimate the volume of the compressed coffee by assuming it is 1.5cm thick.  Using (height)x(surface area of end), I can calculate the volume of the coffee puck as {tex}1.5\pi(5.1/2)^2 \text{cm}^2 = 30.6\text{cm}^2{/tex}.  In a 58mm puck, this works out to {tex}39.6 \text{cm}^2{/tex} which is about 33% more coffee.  I’m inclined to say that the Pavoni is meant to make long single shots, and that if you lift up twice, the second pull should should be brief or cut off.

My recent and fantastic purchase of this musical instrument has made me an unwitting oppressor.  This ocarina is made to play loudly, filling the space you are playing in and matching the volume of other instruments without the need for amplification.  It also fills all four of the units in my house.  For some reason, Karl made a 30 minute video on this, which I have not watched in its entirety (actually I’m watching it now and it’s hilarious, but not as useful as the one I made).  Instead, I took two minutes and a straw to make the silencer in the video below.  Enjoy!