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In preparation for my Specialization exam...

Submitted by gwolf on Wed, 05/27/2015 - 21:17
In preparation for my Specialization exam...
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Feeling somewhat special

Submitted by gwolf on Tue, 05/19/2015 - 18:36

Today I feel more special than I have ever felt.

Or... Well, or something like that.

Thing is, there is no clear adjective for this — But I successfully finished my Specialization degree! Yes, believe it or not, today I can formally say I am Specialist in Informatic Security and Information Technologies (Especialista en Seguridad Informática y Tecnologías de la Información), as awarded by the Higher School of Electric and Mechanic Engineering (Escuela Superior de Ingeniería Mecánica y Eléctrica) of the National Polytechnical Institute (Instituto Politécnico Nacional).

In Mexico and most Latin American countries, degrees are usually incorporated to your name as if they were a nobiliary title. Thus, when graduating from Engineering studies (pre-graduate universitary level), I became "Ingeniero Gunnar Wolf". People graduating from further postgraduate programs get to introduce themselves as "Maestro Foobar Baz" or "Doctor Quux Noox". And yes, a Specialization is a small posgraduate program (I often say, the smallest possible posgraduate). And as a Specialist... What can I brag about? Can say I am Specially Gunnar Wolf? Or Special Gunnar Wolf? Nope. The honorific title for a Specialization is a pointer to null, and when casted into a char* it might corrupt your honor-recognizing function. So I'm still Ingeniero Gunnar Wolf, for information security reasons.

So that's the reason I am now enrolled in the Masters program. I hope to write an addenda to this message soonish (where soonish ≥ 18 months) saying I'm finally a Maestro.

As a sidenote, many people asked me: Why did I take on the specialization, which is a degree too small for most kinds of real work recognition? Because it's been around twenty years since I last attended a long-term scholar program as a student. And my dish is quite full with activities and responsabilities. I decided to take a short program, designed for 12 months (I graduated in 16, minus two months that the university was on strike... Quite good, I'd say ;-) ) to see how I fared on it, and only later jumping on the full version.

Because, yes, to advance my career at the university, I finally recognized and understood that I do need postgraduate studies.

Oh, and what kind of work did I do for this? Besides the classes I took, I wrote a thesis on a model for evaluating covert channels for establishing secure communications.

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Guests in the Classroom: Felipe Esquivel (@felipeer) on the applications on parallelism, focusing on 3D animation

Submitted by gwolf on Fri, 05/08/2015 - 10:44

I love having guests give my classes :)

This time, we had Felipe Esquivel, a good friend who had been once before invited by me to the Faculty, about two years ago. And it was due time to invite him again!

Yes, this is the same Felipe I recently blogged about — To give my blog some credibility, you can refer to Felipe's entry in IMDb and, of course, to the Indiegogo campaign page for Natura.

Felipe knows his way around the different aspects of animation. For this class (2015-04-15), he explained how traditional ray-tracing techniques work, and showed clear evidences on the promises and limits of parallelism — Relating back to my subject and to academic rigor, he clearly shows the speed with which we face Amdahl's Law, which limits the efficiency of parallelization at a certain degree perprogram construct, counterpointed against Gustafson's law, where our problem will be able to be solved in better detail given more processing abilities (and will thus not hit Amdahl's hard ceiling).

A nice and entertaining talk. But I know you are looking for the videos! Get them, either at my server or at

Guests in the classroom: César Yáñez (@caesarcomptus) talks about memory assignation algorithms

Submitted by gwolf on Wed, 04/08/2015 - 11:47

Once again, on March 11 I had a great guest to save me some work and give a talk at my class! This time it was César Yáñez, and he talked about memory management algorithms, emphasizing on ARC.

The video is available, both at this server and in

Thanks a lot!

Guests in the classroom: @Rolman talks about persistent storage and filesystems

Submitted by gwolf on Wed, 11/26/2014 - 10:49

On November 14, as a great way to say goodbye to a semester, a good friend came to my class again to present a topic to the group; a good way to sum up the contents of this talk is "everything you ever wondered about persistent storage".

As people who follow my blog know, I like inviting my friends to present selected topics in my Operating Systems class. Many subjects will stick better if presented by more than a single viewpoint, and different experiences will surely enrich the group's learning.

So, here is Rolando Cedillo — A full gigabyte of him, spawning two hours (including two hiccups where my camera hit a per-file limit...).

Rolando is currently a RedHat Engineer, and in his long career, he has worked from so many trenches, it would be a crime not to have him! Of course, one day we should do a low-level hardware session with him, as his passion (and deep knowledge) for 8-bit arcades is beyond any other person I have met.

So, here is the full video on my server. Alternatively, you can get it from The Internet Archive.

Guests in the classroom: @chemaserralde talks about real time scheduling

Submitted by gwolf on Wed, 10/29/2014 - 15:47

Last Wednesday I had the pleasure and honor to have a great guest again at my class: José María Serralde, talking about real time scheduling. I like inviting different people to present interesting topics to my students a couple of times each semester, and I was very happy to have Chema come again.

Chema is a professional musician (formally, a pianist, although he has far more skills than what a title would confer to him — Skills that go way beyond just music), and he had to learn the details on scheduling due to errors that appear when recording and performing.

The audio could use some cleaning, and my main camera (the only one that lasted for the whole duration) was by a long shot not professional grade, but the video works and is IMO quite interesting and well explained.

So, here is the full video (also available at The Internet archive), all two hours and 500MB of it for you to learn and enjoy!

When Open Access meets the Napster anniversary

Submitted by gwolf on Tue, 10/14/2014 - 11:58

Two causally unrelated events which fit in together in the greater scheme of things ;-)

In some areas, the world is better aligning to what we have been seeking for many years. In some, of course, it is not.

In this case, today I found our article on the Network of Digital Repositories for our University, in the Revista Digital Universitaria [en línea] was published. We were invited to prepare an article on this topic because this month's magazine would be devoted to Open Access in Mexico and Latin America — This, because a law was recently passed that makes conditions much more interesting for the nonrestricted publication of academic research. Of course, there is still a long way to go, but this clearly is a step in the right direction.

On the other hand, after a long time of not looking in that direction (even though it's a lovely magazine), I found that this edition of FirstMonday takes as its main topic Napster, 15 years on: Rethinking digital music distribution.

I know that nonrestricted academic publishing via open access and nonauthorized music sharing via Napster are two very different topics. However, there is a continuous push and trend towards considering and accepting open licensing terms, and they are both points in the same struggle. An interesting data point to add is that, although many different free licenses have existed over time, Creative Commons (which gave a lot of visibility and made the discussion within the reach of many content creators) was created in 2001 — 13 years ago today, two years after Napster. And, yes, there are no absolute coincidences.

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Diego Gómez: Imprisoned for sharing

Submitted by gwolf on Tue, 09/30/2014 - 09:01

I got word via the Electronic Frontier Foundation about an act of injustice happening to a person for doing... Not only what I do day to day, but what I promote and believe to be right: Sharing academic articles.

Diego is a Colombian, working towards his Masters degree on conservation and biodiversity in Costa Rica. He is now facing up to eight years imprisonment for... Sharing a scholarly article he did not author on Scribd.

Many people lack the knowledge and skills to properly set up a venue to share their articles with people they know. Many people will hope for the best and expect academic publishers to be fundamentally good, not to send legal threats just for the simple, noncommercial act of sharing knowledge. Sharing knowledge is fundamental for science to grow, for knowledge to rise. Besides, most scholarly studies are funded by public money, and as the saying goes, they should benefit the public. And the public is everybody, is all of us.

And yes, if this sounds in any way like what drove Aaron Swartz to his sad suicide early this year... It is exactly the same thing. Thankfully (although, sadly, after the sad fact), thousands of people strongly stood on Aaron's side on that demand. Please sign the EFF petition to help Diego, share this, and try to spread the word on the real world needs for Open Access mandates for academics!

Some links with further information:

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Walking without crutches

Submitted by gwolf on Thu, 08/21/2014 - 00:34
Walking without crutches

I still consider myself a newbie teacher. I'm just starting my fourth semester. And yes, I really enjoy it.

Now, how did I come to teaching? Well, my training has been mostly on stages for different conferences. More technical, more social, whatever — I have been giving ~10 talks a year for ~15 years, and I must have learnt something from that.

Some good things, some bad habits.

When giving presentations, a most usual technique is to prepare a set of slides to follow/support the ideas. And yes, that's what I did for my classes: Since my first semester, I prepared a nice set of slides, thematically split in 17 files, with ~30 to ~110 pages each (yes, huge variation). Given the course spans 32 classes (72 hours, 2¼ hours per class), each slide lasts for about two classes.

But, yes, this tends to make the class much less dynamic, much more scripted, rigid, and... Boring. From my feedback, I understand the students don't think I am a bad teacher, but still, I want to improve!

So, today I was to give the introduction to memory management. Easy topic, with few diagrams and numbers, mostly talking about the intuitive parts of a set of functions. I started scribbling and shortening the main points on a piece of paper (yes, the one on the picture). I am sure I can get down to more reduction — But this does feel like an improvement!

The class was quite successful. I didn't present the 100% of the material (which is one of the reasons I cling to my presentations — I don't want to skip important material), and at some point I do feel I was a bit going in circles. However, Operating Systems is a very intuitive subject, and getting the students to sketch by themselves the answers that describe the working of real operating systems was a very pleasant experience!

Of course, when I use my slides I do try to make it as interactive and collaborative as possible. But it is often unfeasible when I'm following a script. Today I was able to go around with the group's questions, find my way back to the outline I prepared.

I don't think I'll completely abandon my slides, specially for some subjects which include many diagrams or pictures. But I'll try to have this alternative closer to my mind.

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Wow. Just rejected an editorial offer...

Submitted by gwolf on Fri, 08/01/2014 - 11:32

Yes, I've been bragging about the Operating Systems book all over... Today, a colleague handed me a phone call from somebody at Editorial Patria, a well known educational editorial in Mexico. They are looking for material similar to what I wrote, but need the material to be enfocado a competencias — Focused on skills, a pedagogic fashion.

I was more than interested, of course. As it currently stands, I am very happy that our book is being used already at three universities in three countries (by the different authors) and have heard other people saying they would recommend it, and of course I'm interested in making our work have as big an impact as possible. Of course, we'd have to modify several aspects of the book to cater to the skills focus... But it would be great to have the book available at commercial bookstores. After all, university editions are never as widely circulated as commercial ones.

I had just one hard request to accept this: Our work must be distributed under a free licensing. Explicitly allow book photocopies and electronic distribution (didn't get into the "and modification" part, but I would eventually get there ;-) )

And... Of course, the negotiation immediately fell down. Editorials, this person says, live from selling individual books. She says she was turned down by another university professor and for another subject this same week.

So, yes, I took the opportunity to explain things as I (and the people that think as I do — Fortunately, not so few) see them. Yes, of course, editorials have to make a living. But text books are often photocopied as it is. Who buys a book? Whoever needs it. On one hand, if somebody will be using a book throughout a semester and it's reasonably priced (say, up to 3×cost of photocopies), they will probably buy it because it just works better (it is more comfortable to use and nicer to read).

If a teacher likes the explanation for a particular topic, it should be completely legal for him to distribute photocopies (or digital copies) of the specific material — And quite probably, among the students, more than one will end up appreciating the material enough to go look for the book in the library. And, as I have done throughout my life, if I read (in copies, electronically or in a library) a book I like... Quite probably I will go buy it.

So... Of course, she insisted it was against their corporate policy. I insisted on my explanation. I hope they meet many stubborn teachers refusing to distribute books under a non-free licensing. I hope I contributed to making a dent in an industry that must change. Yes, a very very small dent, but one that helps them break free from their obsolete mindset ;-)

(But yes, I don't know how long I will regret not being part of their very nice catalog of science and engineering books) ;-) )

Editorial process starting in 3... 2... 1...

Submitted by gwolf on Tue, 07/29/2014 - 13:09


Today I finally submitted our book, Fundamentos de Sistemas Operativos, for the Editorial Department of our institute. Of course, I'm not naïve enough to assume there won't be a heavy editorial phase, but I'm more than eager to dive into it... And have the book printed in maybe two months time!

Of course, this book is to be published under a free license (CC-BY-SA). And I'm talking with the coauthors, we are about to push the Git repository to a public location, as we believe the source for the text and figures can also be of interest to others.

The book itself (as I've already boasted about here :-} ) is available (somewhat as a preprint) for download.

[update] Talked it over with the coauthors, and we finally have a public repository! Clone it from:

Or just browse it from Github's web interface.

Part of the winning black hat team at SGCE2014

Submitted by gwolf on Thu, 06/26/2014 - 00:24
Part of the winning black hat team at SGCE2014

Of course, it was not a hacking contest. Some of the speakers were invited on stage as players in the Developers bowl (a Jeopardy-like game) at Software Gurú Conference & Expo 2014. I happened to be in the winning team :-)

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Presenting Kaz!

Submitted by gwolf on Mon, 05/19/2014 - 16:27
Presenting Kaz!

My guest and good friend Kaz, ready to start explaining the ext4 filesystem (and kernel module)

Kaz explaining ext4

Submitted by gwolf on Mon, 05/19/2014 - 16:25
Kaz explaining ext4

Kaz explaining ext4

Submitted by gwolf on Mon, 05/19/2014 - 16:19
Kaz explaining ext4
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