Pedro Assunção » Uncategorized

Computers and jumps

Pedro Assunção — Sat, 27 Dec 2008 15:48:20 +0000

I’ve been loving my Mac Book Pro so far. OSX is, without a doubt, one of the most brilliant pieces of software engineering I have ever encountered; I almost feel sorry for not “going mac” earlier in my life.

But, no matter how good it is, the only thing that has been going constantly through my mind lately is the thought of jumping again. I have been doing some spare time math, figuring out how much time one can spend in free fall (with and without a winged suit). I think once I do the AFF course (Accelerated Free Fall) I will be addicted for good

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Some photos of the jumps

Pedro Assunção — Thu, 25 Dec 2008 23:11:51 +0000

Get them here: 20081221_First_Parachute_Jumps

The most cool ones should follow, as soon as I get the CD from the school guys

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Should go to bed now :)

Pedro Assunção — Wed, 24 Dec 2008 03:33:02 +0000

Bought a new mac book pro. Like with most new toys, I cannot stop playing with it. It’s 3.30 in the morning and I should go to bed. But somehow the evil apple still holds me tight in front of the laptop

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The aftermath of the jumps

Pedro Assunção — Sun, 21 Dec 2008 20:08:36 +0000

I cannot begin to describe what I've jump been through. The mix of feelings of the first jump out of an airplane is absolutely mind blowing! My best take at describing it would be something in the lines of "to be born again". Only because the experience is as traumatic (in the best sense possible) as the one we endure on birth.

The course I attended was called automatic opening. Though, as far as I'm concerned, the accelerated free falling (AFF) course only extends it in terms of more time in the air and the maneuvers executed while in free fall. That and more jumps, of course; The automatic opening is comprised of 4 jumps while the AFF is 8 jumps or more.

But back to this one. The excitement and adrenalin levels on the ground were only exceeded once the airplane took off. It's not your standard commercial airlines aircraft; Even though the take off is fairly smoother than in a jet plane, any faster motion in mid-air will make your stomach jump with that awesome feeling of temporary weightless. Each of us popcorn jumpers (the kind term to refer to automatic opening students) was endowed with a magical altimeter which measures, hey, the altitude. When it reached around 3500 feet the door was opened and I knew then that we were in trouble

The signal was given to one of my colleagues to go for the door and, finally, to jump outside the damn plane!!! Now, I was expecting to go crazy with my own feelings, but I never thought that the face of another person jumping out of an airplane for the first time would make such a strong impression on my brain. My good friend Ricardo's expression of panic, terror, and adrenalin while leaving the plane will never leave my mind, as long as I live. Priceless!

Then one more student jumped (again, panic, terror, all of that ) and, suddenly, it was my turn. I positioned myself near the door, waiting for the instruction to jump. I think I might have been pretty mentally numb by now, because I only remember a couple of frames of the first jump. That and the feeling of what seemed like the giant arms of a monster called gravity, pulling me down with as much strength as I never felt before. I was reborn, literally.

After the initial shock, and following the instructions given in the course, I checked my wing to see if everything was fine (did it open? properly? nothing weird going on?). The problem is I've never seen a parachute opened above me so it took me some time to make sure that thing was actually sustaining me in the air, and that I could fly it to the ground.

In the second and third jumps the feelings of terror and panic went significantly down turning, instead, into feelings of overwhelming freedom and awesomeness. After the second jump, the guy that was responsible for providing assistance for the landings told us that you could do something like a pendulum effect on the parachute. It consists of pulling both handles (to make the chute literally stop in the air) and releasing them instantly. This makes the wing jump really fast to the front of you and your body, as you might have guessed, will free fall for a couple of meters, giving that fucking great feeling of jumping out of the plane once again. Mix with some down spirals and you have a good way of curing yourself of the fear of falling, I tell you that

The landings are actually reaaaaaaaaaaaaally easy. Go to the spot (following some more protocol, which I'll skip) turn against the wind, let it fly and drop, and when at around 1-2 meters of the floor pull both handles down (to break). It takes some sensitivity to get it right. But after the first jump you will be able to pull it off almost like a pro.

And there you go. Pictures and videos will follow, as soon as I get them from the school (since I could not take the camera with me for some first person footage).

I STRONGLY recommend this to everyone. You will not regret it

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The 30th row

Pedro Assunção — Thu, 18 Dec 2008 14:03:31 +0000

I've always been curious about experimenting with different seats inside airplanes so, in this entry, I will try to sum up my conclusions about traveling on the 30th (the last) row of a Boeing 737-800, from Amsterdam to Lisbon with KLM Airlines (now AirFrance).

I would assume I was going to get less stress and confusion seating there than, say, the middle of the airplane. I was wrong.

The first thing I noticed, when reaching my seat, was that both the baggage compartments for these 3 rows (28, 29 and 30) were already filled with KLM stuff. I ended up having to put my jacket 5 or 6 rows further up the aircraft. Not a good start; if you don't have enough space to put all your crap, KLM, get bigger planes! Don't make people have to pay for it.

I sat down. The first thing I noticed was that this is the only freaking row on the airplane where the seats don't recline back. That really pissed me off, since I could no longer make use of this uber cool inflatable pillow I bought. Another thing that was really bad – though, in truth, I never noticed – was that at least in the 30C (mine) and 30D aisle seats there is this metal thing keeping the seat in front more stable, which kind of reduces the space available for my feet. Not sure if it's there in all aisle seats, but it's kind of annoying.

Now a bit of good news for those that want to experience a lot more turbulence that in the middle of the plane: You get the food first, since one of the trays goes into the front, and another starts from the back (you are in the last row, after all). This would be actually a good thing, except that the food was crap. Ok, it was shit. No, I take that back; I have tasted shit that was better. That particular corgette salad was inedible and the bread, I'm pretty sure, had been baked the day before. After the food, and as usual, I got the choice amongst several sweets. I went for the lolly pop. I figured that if this company treats me like I'm 6 years old, and have no conscience whatsoever of how much they are robbing me, I might as well continue the child-like behavior.

Now that the good news are done, let's go back to the crap. Literally! This seat is back to front with the bathroom doors. This means that, from times to times, you will get this really awesome (make that awe "full") sky breeze that will make you return the food you already ingested. That, combined with the fact that you will get dozens of air toillet users passing through you during the flight, will make for an extremely rewarding flight experience. One that you will never forget, at least.

To make it really really awesome, my laptop's battery was at 5% when the plane lifted off…

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Thoughts on non-opening parachutes…

Pedro Assunção — Tue, 16 Dec 2008 11:47:44 +0000

With 95 hours until my first jump, I started reading some stuff (maybe I shouldn't) regarding what can go wrong. This one (http://www.wikihow.com/Survive-if-Your-Parachute-Fails-to-Open) stroke me as especially motivating and positive.

With that in mind, here are my next steps before the jump. I hope they will be of some use for future first time jumpers, but maybe some regulars can also take some ideas from it:

By no special order:
1. Write down (and give it to someone trustworthy) all my passwords;
– Websites with important/interesting information (bookmarks, business stuff, online banking, bank investments, etc.);
– Blogs;
– Email accounts.
2. Write down important document numbers;
– Identity card;
– Taxes;
– Bank cards.
3. Kiss and hug as much people I love as I can before the jump;
4. I don't think it's time for me to write a will, so I think everyone can just fight for my stuff. Consider it a last request ;D

So, to sum it up for now, excitement is building up and I'm sure it will only get worse/better over the next few days. I am absolutely sure that the jump will be amazing and something I will never forget, for the rest of my life. The adrenalin that will go through my brain will be incredible, I can imagine, and the silence that will follow the parachute's deployment will surely be heavenly.

Pedro

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Some notes on scalability

Pedro Assunção — Thu, 11 Dec 2008 11:09:35 +0000

I have been wanting to write this forever, also so I could remind myself of it whenever needed. And this is the kind of subject that traverses most programming languages/frameworks/systems as long as you are dealing with large quantities of data.

There are probably more things one can do in order to allow an application to scale up easily, but these are the ones I have put in place in the past and it has worked out nicely so far:

Read/write splitting (master/slave replication)
If possible (e.g. if you are not using some kind of really restrictive database access framework (think django, as it is right now ), put in place mechanisms to allow you to read data from multiple slave DB machines with some strategy to choose between them (round robin, last used, most load, etc.). This will allow you to scale up reading from your database.

Streaming directly from the database to prevent a lot of in-memory data coming from DB
I came in contact with this particular problem when having to send clients a bunch of processed data from a database. Whenever possible shift all the work on the data to the database (SQL) and then stream the data to the client through your application. What I mean by this is: don't keep data in memory in your application as most as possible. For instance MySQL, by default, will not stream the data to your application; it will actually keep the rows in memory and then send them to the client. If you have requests of 50 Mb worth of data you can see where your server is going after 30 concurrent requests (hint: morgue).

Caching
Cache your requests whenever possible. Use an out of the box solution (like squid for example) or develop your own strategy to cache data, so you hit your databases as least as possible.

Data discretization
This one is related to caching. Figure out clever ways of discriminating your data so it's easier to cache. For instance, imagine you are serving a bunch of data, that people submit to you, to everyone else. Anytime someone submits something you will have data that can be sent to everyone else. Instead of making this data immediately available, make it discrete. Serve batches of data, say, once a day. This will allow you to cache daily requests easily with squid, for example.

Hibernate second level cache
For java/spring/hibernate developers out there: Do make use of hibernate's second level cache. Especially for content that does not change that often. It will pay off especially for web interfaces. For data distribution I would recommend not using hibernate at all. Think plain JDBC with some (earlier mentioned) different caching solution and streaming the results directly.

Data redundancy where it makes sense
Don't worry about sacrificing disk space on the database cluster in favor of faster query times. Especially good when searching content on your database. That one extra redundant column in your data table will make the search much faster than using joins all over the place.

These are my thoughts on scalability. I would love to hear about your experiences and solutions on this field.

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236 hours until my first airplane jump

Pedro Assunção — Wed, 10 Dec 2008 14:36:54 +0000

Getting excited, so I setup an online stopwatch hahahaha

http://www.7is7.com/otto/countdown.html?year=2008&month=12&date=20&hrs=10&ts=24&min=0&sec=0&tz=0&lang=en&show=h&mode=r&cdir=down&bgcolor=%23FFFFFF&fgcolor=%23000000&title=Countdown%20to%20my%20first%20airplane%20jump

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Way to wait for all threads to finish in Python

Pedro Assunção — Tue, 25 Nov 2008 10:15:06 +0000

Not sure if it's the best way, but I found this example in an webarchive page and it kind of makes more sense than keeping a list of the threads and cycling all the time checking if they are active or not:

while threading.activeCount()>1:
sleep(1)

Not sure if this works, but have to try

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My computer

Pedro Assunção — Mon, 17 Nov 2008 14:41:38 +0000

My computer is amazing. He (I will always refer to it as an entity, even though I am aware that *it* is still not aware of itself) is capable of executing a tremendous amount of operations per second and, yet, it's not capable of remembering and asking for (in a smart way) where do I want to store something I download.

I am aware that there are probably a lot of (academic?) projects out there set to change this and make machines do what they are actually supposed to do: make my life easier. There is one movie that recently as reinforced this idea in my mind (no, not minority report) and that is the new Iron Man movie. That is exactly how I see computers: Working with us to actually help us be more creative, productivem, and efficient. Not just dumb machines that know how to store bits, but extensions to our own work.

That being said, and my frustration put out in the open, I ask if there is anyone out there doing anything even remotely close to this: Creating some kind of smart interface on top of (any, preferably linux ) operating system that is gifted with some kind of, at least, memory and inquisitive engine that, when presented with something it does not understand, would ask and learn, instead of throwing an exception or a segmentation fault.

Here's a use case (directly adapted from Iron Man): I'm browsing the web and I find a torrent for a new cool linux distro that I want to try out. I tell my computer "download this" and, by now, he already knows that a torrent is supposed to be download in a given way. What he does not know is where to store the actual contents of the file. I mean, there are just so many drives in my home network, all discoverable through avahi, bonjour, or other service discovery architectural flavour. So where should he put it? He asks and I tell him (tell being the keyword, think speech recognition, but not literally like "c:/somewhere/distros/linux", more like "create me a new place for linux distros"). The next time he should still ask, but this time if I want it in the linux distros also. And I should be able to say something like "from now on, store all distros in that place, unless I say otherwise when downloading", if I feel really lazy".

That is the kind of stuff I would expect to be available today, when the amount of computational power in the world is imense, but personal computers are still as dumb as they were in the times of punctured cards. Alright, maybe an overstatement, but still…

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