I came across MIT’s course Structure and Interpretation of Computer Programs course today. The accompanying text-book is freely available online and also video of the lectures are available from the Internet Archive.
This course has a great reputation for being difficult and teaching pretty advanced functional programming techniques. Very cool that it is freely available for study. I’m having fun going through it now.
One of my personal challenges in physical activities (martial arts, Yoga, weightlifting) has always been flexibility. Some people have quite naturally good flexibility, others have to work on it. What exactly is flexibility? There is a very common perception that flexibility is a physical characteristic - that its a question of muscle, ligament and tendon length. Stretching exercises, therefore, are thought to result in physical lengthening of the body parts resulting in increased flexibility.
Numerous authorities have a radically different view on this. Tom Kurz, Pavel Tsatsouline and even a professor of kinesiology at UC Chico (Duane Knudsen - see this recent NYTimes article) have very changed perspectives about flexibility and stretching.
Their thinking is that flexibility is not a physical restriction - that is, you are not limited by the length of your muscles or ligaments or tendons - but rather by the programming of your nervous system, which is not under your conscious control. While under anesthetic, for example, a surgeon can rotate your shoulder a full 360 degrees. An experiment used by both Tom Kurz and Pavel Tsatsouline using the side splits is to lift one leg at a time into the splits position, like the photo below illustrates:
If you can do this with each leg, you have shown that it is not a physical restriction that prevents you from doing the full side splits. There is no tissue connecting each leg to one another, which means that something else is stopping you from performing the splits. That “something else” is your nervous system. The theory is that your unconscious nervous system imposes these restrictions on how far it will let you stretch your muscles. Flexibility training, then, should concern itself with reprogramming the nervous system to let you stretch further. This is precisely what the programs of Tom Kurz and Pavel Tsatsouline are concerned with.
For some free information on the kinds of stretching programs (typically known as “dynamic stretches”) I recommend Tom Kurz’s free column, “Stretch Yourself”. Good luck with your training!
I’ve written a little bit about Nassim Nicholas Taleb before. In particular, I posted a short snippet to implement Monte Carlo simulation in Python.
Anyway, I’ve lately been reading Wittgenstein’s On Certainty. In this book, published after his death, he writes about the connections between human language and logic - and the nature of knowledge itself.
Especially these days, with absurdly complicated financial crises and so on taking place, and with seemingly no good understanding of the situation, the field of epistemology (theory of knowledge) seems quite practical and relevant indeed. Of course, Taleb has written extensively about epistemology applied to finance, in particular with his black swan “theory”.
In this context, its very interesting to take note of Wittgenstein’s writing in On Certainty. For example:
80. The truth of my statements is the test of my understanding of these statements.
81. That is to say: if I make certain false statements, it becomes uncertain whether I understand them.
It would seem to me that many people have forgotten these rather fundamental ideas. Why are we still paying any attention to people like Henry Paulson and ‘Helicopter’ Ben Bernanke? An English translation of On Certainty is freely available on the web.
I’m in Ireland for the holidays, and I’m trying to keep up some training while I’m away from the gym. At least I managed to find a couple of 30lbs dumbbells at the house, that increased versatility a lot:
The squat is an exercise I’ve really come to appreciate of late. The difficulty and importance of this movement cannot be underestimated. While the squat is in fact a very natural and innate movement - witness young children do this effortlessly all the time. However, years of sitting in chairs and other things conspire to greatly reduce our ability to perform the squat.
Everyone can benefit from the squat - most obviously, it enables you to pick up and lift things without causing injury to the back. It helps flexibility and can be used as a tough conditioning exercise. Especially I think its important for people - like me - who spend most of their time sitting a desk, to practice this movement.
The key to the squat is good form. Its easy to do a bad squat. Take the time to learn it properly, and to work on the correct technique. Personally, I had a lot of trouble getting low enough in my squat until my coach pushed me to a) keep my knees pressed outwards and b) hold my arms up overhead. Once I internalised those two things, my squat form improved a huge amount.
One common issue with the squat is rounding out of the lower back. I came across this great video tutorial for the squat, which describes the problem in detail and prescribes various fixes to get past that. Some highly valuable pointers in this one:
I mentioned the Fran routine in a post last week. Along with pull-ups, the workout consists of thrusters. Although I don’t think my thruster is terrible, I definitely need to improve it. I find my shoulder flexibility a limiting factor, causing me to expend more energy than necessary, and power is definitely a factor at higher weights. I think my overhead squat technique is pretty decent, but maintaining good form with weight and at speed is tough.
I came across this video of a dude giving some decent tips on the thruster here:
I can’t take credit for this one. No, I’m merely acting as a conduit for a recipe created by my lovely girlfriend, Feifei, who has cooked this wonderful dish on a number of occasions. She kindly agreed to tell me the secret components of this steak marinade, and I’m naming it after her.
Steak a la Feifei
Serves two.
Preparation
Mix the marinade in a small dish with high sides - whatever size container you have that will accommodate the steaks submerged into as much marinade as possible. Cut into the steaks so that they can absorb more marinade, then place in dish with marinade, for at least 15 minutes per side. Be sure to cover the steaks thoroughly. When steaks have been soaked in marinade for around a half an hour, cook the steaks. Feifei used a George Foreman contact grill. Whatever you use, cook the steaks in the marinade - pouring it over it. On the George Foreman, it took around 5-6 minutes to cook the steaks so they were medium.
Serve and enjoy!
I did the CrossFit Fran routine for the first time last night at the gym. It consists of just two exercises - thrusters at 95 lbs and pull-ups. You do 21-15-9 of each, alternating. In other words, 21 thrusters, then 21 pull-ups, before moving down to 15 thrusters - you get the picture. If you’re not familiar with the thruster, its essentially a squat with an over head push press, just like this video shows:
You do this for time. Mine wasn’t anything to write home about - 11 minutes 10 seconds. There are people who can bang this out in 2 minutes. I was happy enough with the thrusters but the pull-ups really slowed me down. I don’t have the kipping technique at all yet. Really great test of strength though. Today is my rest day, but I’m looking forward to focusing on thrusters and pull-ups over the coming months, and getting my time way down.
For quite a long time now, OpenBSD has, among numerous exploit mitigation techniques, had a very strict mmap()-based malloc() implementation. Recently re-written by Otto Moerbeek, it is even harsher now. I find that this feature makes OpenBSD one of the best platforms to develop C programs on. If you have a double-free, use-after-free, off-by-one, or other typical mistake in your program, chances are OpenBSD’s omalloc will trip up on it eventually. Especially on a strict-alignment, long-pointer architecture like sparc64, running it under OpenBSD is a great way to gain confidence that your program is solid.
Anyway, recently Otto has made OpenBSD’s malloc even stricter. I upgraded my home machine over the weekend to the latest snapshot with these commits, and I’m currently running a bunch of Unworkable BitTorrent download processes on it to make sure my code still holds up. So far so good!
If you have some C code you care about, I’d recommend taking the time to run it under OpenBSD for a while - you might find you catch some bugs which even Valgrind missed. Enjoy!
I think food is one of the most basic things in life. Most people eat around three times a day, every day, for their entire life. How food tastes, and what it does to your body, would seem to me to be absolutely critical. Few people here in the San Francisco tech industry seem to cook for themselves, or pay much attention to the kind of stuff they put into their bodies, which I find quite bizarre. The culture of consuming vast quantities of heavily refined sugars (via sodas, donuts, pastries, icecream and all that junk) along with highly processed carbohydrates (pizza, bread, potato chips, etc) along with plenty of fatty, fried foods, seems completely insane. And then people wonder why they are overweight, and suffer from all manner of health problems - diabetes, heart disease, and of course deadly cancers.
While I don’t advocate going crazy and completely cutting out entire food groups willy nilly - probably such an effort will be unsuccessful in the long run, and almost certainly decrease your overall happiness and emotional well being - I do think its important for people to reclaim their connection to food and at least choose their own ingredients, cooking methods, and generally go through life being aware of the details of food. If ever details are important, its the details pertaining to food.
Anyway, on to this week’s recipe. Andronico’s had organic New York Steak on special, so I bought a nice cut and cooked it.
Allspice Steak with Broccoli and Shitake Mushrooms
Preparation:
A friend of mine, Chris, who is a fantastic cook (and chefs professionally) once told me the secret to good tasting steak is salt. While my steak isn’t as good as his, he’s certainly right about the salt. Rub both sides of the steak with plenty of salt, and then rub in the allspice. I cooked mine on a George Foreman, but you can easily do its under your own non-contact grill or even use a pan. I like my steaks to be done medium, so I cooked it for around 6-7 minutes. In the meantime, I finely chopped the shitake mushrooms and coarsely broke up the brocolli crown (I like brocolli coarse). Shitake mushrooms are well-known for not only their anti-cancer properties, but a whole myriad of health benefits such as anti-viral effects, thrombosis reduction, and so on. Brocolli, like all cruciferous vegetables, have tons of health-promoting qualities. Both of these foods taste great, too. So, dump your veggies in a pan with some water and sautee until they’re done to your liking. I like mine on the less-cooked side. Serve and enjoy!
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