Archive for October 2013

Hungarian rotation

The 2013 Informatics Europe “Best Practices in Education” award was devoted, this year, to initiatives for teaching informatics in schools [1].  It was given out last week at the European Computer Science Summit in Amsterdam [2]. Two teams shared it, one from Poland and the other from Romania. Both teams showed excellent projects, but the second was beyond anything I expected.

The project comes from the Hungarian-speaking Sapientia University in Transylvania and is devoted to teaching algorithms visually and “at the same time enhancing intercultural communication” in the region. It illustrates the classical sorting algorithms through folk dances. Quicksort is Hungarian, selection sort is gypsy, merge sort is “Transylvanian-saxon”. I think my favorite is Shell sort [3]. For more, see their YouTube channel [4].

Now  if only they could act the loop invariants [5].

References

[1] 2013 Best Practices in Education award, see here.

[2] 2013 European Computer Science Summit, here.

[3] “Shell sort with Hungarian (Székely) folk dance”, see here.

[4] YouTube Algorythmics channel, here.

[5] Carlo Furia, Bertrand Meyer and Sergey Velder: Loop invariants: Analysis, Classification and Examples, in ACM Computing Surveys, Septembre 2014, to appear, available here.

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The secret of success

In the process of finishing a book right now, it occurred to me that writing is really a simple matter. There are only three issues to address:

  1. How to start.
  2. How to finish.
  3. How to take care of the stuff in-between.

In the early stages  (1) you face the anguish of the “empty paper, defended by its whiteness” (Mallarmé) and do not know where to begin. If you overcome it, you have all the grunt work to do (3), step after step. At the end (2), while deep down you feel you have done enough and should be permitted to  click “Publish”, you still have to fill the holes, which may be small in number but have remained holes for a reason: you have again and again delayed filling them because in reality you do not know what to write there.

All things considered, then, it is not such a big deal.

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Reuse of another kind

This is a plug for a family member, but for a good cause: reuse and the environment. There are many reasons for promoting reuse in software; in other fields some of those reasons apply too, plus many others, economic and environmental. The core concern is to reduce waste of all kinds.

One of the most appalling sources of waste is the growing use of throw-away food containers. It is also avoidable.

A new company, bizeebox [1], has devised an ingenious scheme to let restaurants use containers that can be washed and reused many times. It is easy to use by both restaurants and customers, saves money, and avoids heaping tons of waste on landfills. Their slogan: “Take the Waste Out of Takeout“.

The founders of bizeebox have run successful pilot projects and are now starting for real with restaurants in the Ann Arbor area. They have launched a campaign on Indiegogo, with a $30,000 funding goal. Reuse deserves a chance; so do they.

References

[1] bizeebox page, at bizeebox.com.

[2] bizeebox Indiegogo campaign: here.

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The laws of branching (part 2): Tichy and Joy

Recently I mentioned the first law of branching (see earlier article) to Walter Tichy, famed creator of RCS, the system that established modern configuration management. He replied with the following anecdote, which is worth reproducing in its entirety (in his own words):

I started work on RCS in 1980, because I needed an alternative for SCCS, for which the license cost would have been prohibitive. Also, I wanted to experiment with reverse deltas. With reverse deltas, checking out the latest version is fast, because it is stored intact. For older ones, RCS applied backward deltas. So the older revisions took longer to extract, but that was OK, because most accesses are to the newest revision anyway.

At first, I didn’t know how to handle branches in this scheme. Storing each branch tip in full seemed like a waste. So I simply left out the branches.

It didn’t take long an people were using RCS. Bill Joy, who was at Berkeley at the time and working on Berkeley Unix, got interested. He gave me several hints about unpleasant features of SCCS that I should correct. For instance, SCCS didn’t handle identification keywords properly under certain circumstances, the locking scheme was awkward, and the commands too. I figured out a way to solve these issue. Bill was actually my toughest critic! When I was done with all the modifications, Bill cam back and said that he was not going to use RCS unless I put in branches. So I figured out a way. In order to reconstruct a branch tip, you start with the latest version on the main trunk, apply backwards deltas up to the branch point, and then apply forward deltas out to the branch tip. I also implemented a numbering scheme for branches that is extensible.

When discussing the solution, Bill asked me whether this scheme meant that it would take longer to check in and out on branches. I had to admit that this was true. With the machines at that time (VAXen) efficiency was important. He thought about this for a moment and then said that that was actually great. It would discourage programmers from using branches! He felt they were a necessary evil.

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Another displaced business

Front-page notice in yesterday’s Tages Anzeiger (one of the principal Swiss newspapers):

Dear Readers:

From today the employment-ads section will no longer appear as a separate supplement, but directly as a section of the Tuesdays and Thursday paper. The reason is the ever smaller number of position offerings.

It seems clear that what has decreased is not the number of positions offered — the job market in Switzerland is healthy — but the number of those offered through newspapers. End of an era.

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