datadataeverywhere

Karma: 784

datadataeverywhere 18 Sep 2012 4:00 UTC
1 point
in reply to: Jayson_Virissimo’s comment on: Open Thread, September 15-30, 2012
Indeed, I misinterpreted you in multiple ways. My model went something like “Jayson_Virissimo is currently working 60-80 hours a week on his start-up. Once it exceeds ramen-profitability, he intends to scale back his efforts to become a full-time student.” How very foolish of me!

datadataeverywhere 18 Sep 2012 2:19 UTC
1 point
in reply to: bogus’s comment on: Checking for the Programming Gear
I certainly hope that I’m not confused about my word choice. I write compilers for a living, so I might be in trouble if I don’t understand elementary terms.

In all seriousness, my use of the word “scope” was imprecise, because the phenomenon I’m describing is more general than that. I don’t know of a better term though, so I don’t regret my choice. Perhaps you can help? Students that I’ve seen have difficulty with variable substitution seem to have difficulty with static scoping as well, and vice versa. To me they feel like different parts of the same confusion.

In a related note, I once took some of my students aside who where having great difficulty getting static scoping, and tried to teach them a bit of a dynamically-scoped LISP. I had miserable results, which is to say that I don’t think the idea of dynamic scope resonated with them any more than static scope; I was hoping maybe it would, that there were “dynamic scoping people” and “static scoping people”. Maybe there are; my experiment is far from conclusive.

EDIT: Hilariously, right after I wrote this comment the newest story on Hacker News was http://news.ycombinator.com/item?id=4534408, “Actually, YOU don’t understand lexical scope!”. To be honest, the coincidence of the headline gave me a bit of a start.

datadataeverywhere 18 Sep 2012 2:04 UTC
2 points
in reply to: Jayson_Virissimo’s comment on: Open Thread, September 15-30, 2012
A little. As your income increases, I expect your consumption to become more expensive in monetary terms, but as your business grows I expect the value of your time to increase and for your consumption patterns to become less expensive in terms of time. College is very expensive in terms of time.

I’m not saying this is a bad choice, but it is one that surprises me. I’m still interested in the answers to my questions. Do you intend to sell your start-up, have it run itself, or abandon it? It seems like those options cover the gamut (I might consider requiring < 40 hours a week of your time to be “running itself”; if you’re quite dedicated, you could probably fit being a full-time student in even with the start-up taking 40+ hours of your time, making that an alternative option).

datadataeverywhere 16 Sep 2012 20:19 UTC
0 points
in reply to: NancyLebovitz’s comment on: Checking for the Programming Gear
My post didn’t indicate this, but the most common source of scope is functions; calling a function starts a new scope that ends when the function returns. Especially in this case, it does often make sense to use the same variable name:
```
posterior = ApplyBayes(prior, evidence)
...
function ApplyBayes(prior, evidence) = { ... }
```
Will have prior=prior, evidence=evidence, and is a good naming scheme. But in most languages, modifying ‘evidence’ in the function won’t affect the value of ‘evidence’ outside the scope of the function. This sometimes becomes confusing to students when the function above gets called like so:
```
posterior = ApplyBayes(prior, evidence1)
posterior = ApplyBayes(posterior, evidence2)
posterior = ApplyBayes(posterior, evidence3)
```
Because their previous model relied on the names being the same, rather than the coincidence of naming being merely helpful.

Overall, I would say that this is still a fertile source of errors, but in some situations the alternative is to have less readable code, which is also a fertile source of errors and makes fixing them more difficult.

datadataeverywhere 16 Sep 2012 3:14 UTC
5 points
in reply to: Jayson_Virissimo’s comment on: Open Thread, September 15-30, 2012

...going back to school to study computer science (if my start-up succeeds before then).

That’s amusing. Usually I would say the value of the founder being present is much higher for a successful company than one that has failed. I would actually expect my freedom to pursue other avenues diminish as my success in my current avenue grows.

Do you mean that your start-up, if successful, will pretty much run itself? Or that if it hasn’t succeeded /yet/, then you will feel obligated to stay and keep working on it?

datadataeverywhere 16 Sep 2012 3:08 UTC
6 points
in reply to: [deleted]’s comment on: Open Thread, September 15-30, 2012
Of all my flaws, I currently consider my bias to thought (and study, research, etc.) over action my greatest. I suspect that LessWrong attracts many (a disproportionate number of) such people.

datadataeverywhere 15 Sep 2012 6:44 UTC
2 points
in reply to: siodine’s comment on: Checking for the Programming Gear
Not too long ago, I lost a week of work and was able to recompose it in the space of an afternoon. It wasn’t the same line-for-line, but it was the same design and probably even used the same names for most things, and was roughly 10k LOC. So if I had recent or substantial experience, I can see expecting a 10x speedup in execution. That’s pretty specific though; I don’t think I have ever had the need to write something that was substantially similar to anything else I’d ever written.

Domain experience is vital, of course. If you have to spend all your time wading through header files to find out what the API is or discover the subtle bugs in your use of it, writing just a small thing will take painfully long. But even where I never have to think about these things I still pause a lot.

One thing that is different is that I make mistakes often enough that I wait for them; working with one of these people, I noticed that he practiced “optimistic coding”; he would compile and test his code, but by feeding it into a background queue. In that particular project, a build took ~10 minutes, and our test suite took another ~10 minutes. He would launch a build / test every couple of minutes, and had a dbus notification if one failed; once, it did, and he had to go back several (less than 10, I think) commits to fix the problem. He remembered exactly where he was, rebased, and moved on. I couldn’t even keep up with him finding the bug, much less fixing it.

The people around here who have a million lines of code in production seem to have that skill, of working without the assistance of a compiler or test harness; their code works the first time. Hell, Rob Pike uses ed. He doesn’t even need to refer to his code often enough to make it worthwhile to easily see what he’s already written (or go back and change things)---for him, that counts as an abnormal occurrence.

datadataeverywhere 14 Sep 2012 20:59 UTC
0 points
in reply to: siodine’s comment on: Checking for the Programming Gear
I don’t know about you, but I can’t recall 10k LOC from experience even if I had previously written something before; seeing someone produce that much in the space of three hours is phenomenal, especially when I realize that I probably would have required two or three times as much code to do the same thing on my first attempt. If by “reciting from experience” you mean that they have practiced using the kinds of abstractions they employ many times before, then I agree that they’re skilled because of that practice; I still don’t think it’s a level of mastery that I will ever attain.

datadataeverywhere 12 Sep 2012 23:33 UTC
2 points
in reply to: NancyLebovitz’s comment on: Checking for the Programming Gear
In my opinion, almost all of that 50% (that drop out) could program, to some extent, if sufficiently motivated.

A great deal of Computer Science students (half? more than half?) love programming and hit a wall when they come to the theoretical side of computer science. Many of them force themselves through it, graduate, and become successful programmers. Many switch majors to Information Technology, and for better or for worse will end up doing mostly system administration work for their career. Some switch majors entirely, and become engineers. I actually think we do ourselves a disservice by failing to segment Computer Science from Software Engineering; a distinction made at very few institutions, and when made, often to the detriment of Software Engineers, regrettably.

So to answer your question; of the 50% that drop out, I think most end up as sub-par programmers, but 80% of that 50% “have programming gear”, to the extent that such a thing exists.

datadataeverywhere 12 Sep 2012 13:04 UTC
13 points
in reply to: NancyLebovitz’s comment on: Checking for the Programming Gear
I’ve taught courses at various levels, and in introductory courses (where there’s no guarantee anyone has seen source code of any form before), I’ve been again and again horrified by students months into the course who “tell” the computer to do something. For instance, in a C program, they might write a comment to the computer instructing it to remember the value of a variable and print it if it changed. “Wishful” programming, as it were.

In fact, I might describe that as the key difference between the people who clearly would never take another programming course, and those that might—wishful thinking. Some never understood their own code and seemed to write it like monkeys armed with a binary classifier (the compiler & runtime, either running their program, or crashing) banging out Shakespeare. These typically never had a clear idea about what “program state” was; instead of seeing their program as data evolving over time, they saw it as a bunch of characters on the screen, and maybe if the right incantations were put on the screen, the right things would happen when they said Go.

Common errors in this category include:
- Infinite loops, because “the loop will obviously be done when it has the value I want”.
- Uninitialized variables, because “it’s obvious what I’m computing, and that you start at X”.
- Calling functions that don’t exist, because, “well, it ought to”.
- NOT calling functions, because “the function is named PrintWhenDone, it should automatically print when the program is done”.
These errors would crop up among a minority of students right up until the class was over. They could be well described by a gut-level belief that computers use natural language; but this only covers 2-6% of students in these courses*, whereas my experience is that less than 50% of students who go into a Computer Science major actually graduate with a Computer Science degree; so I think this is only a small part of what keeps people from programming.

*In three courses, with a roughly 50-person class, there were always 1-3 of these students; I suspect the median is therefore somewhere between 2 and 6%, but perhaps wildly different at another institution and far higher in the general population.

datadataeverywhere 12 Sep 2012 12:31 UTC
3 points
on: Checking for the Programming Gear
I’ve taught C, Java and Python at a university and (a little) at the high school level. I have noticed two simple things that people either surmount or get stuck on. The first seems to be even a basic ability to keep a formal system in mind; see the famous Dehnadi and Bornat paper. The second, I have heard less about: in programming, it’s the idea of scope.

The idea of scope in almost all modern programming languages goes like this:
- A scope starts at some time (some place in the code), and ends somewhere later.
- A scope can start before another ends; if so, it has to end before the “outer” scope.
- Inside a scope, objects can be created and manipulated; generally even if another scope has started.
- Unless something special is done, objects no longer exist after a scope ends.
- Pivotally (this seems to be the hardest part), a objects can be created with one name in an outer scope and be referred to by a different name in an inner scope. Inner scopes can likewise create and manipulate objects with the same names as objects in an outer scope without affecting the objects in that outer scope.
It’s really hard for me to think of an analogous skill in the real world to keeping track of N levels of renaming (which may be why it gives students such difficulty?). The closest I can think of is function composition; if you don’t have to pick your way through symbolically integrating a composed function where the variables names don’t match, I have pretty high confidence that you can manage nested scopes.

EDIT: There are two other, well-known problems. Recursion and pointers. I’ve heard stories about students who were okay for a year or two of programming courses, but never “got” recursion or, never understood pointers, and had to change majors. I’ve seen students have enormous difficulty with both; in fact, I’ve passed students who never figured one or the other out, but managed to grind through my course anyway. I don’t know whether they dropped out or figured it out as their classes got harder—or just kept faking it (I had team members through grad school that couldn’t handle more than basic recursion). I’m not inclined to classify either as “programming gear” that they didn’t have, but I don’t have data to back that up.

datadataeverywhere 12 Sep 2012 11:58 UTC
0 points
in reply to: DanArmak’s comment on: Checking for the Programming Gear
For the record, I think programming is so measurable and has such a tight feedback loop that it is one arena in which it’s relatively easy to recognize ability that far exceeds your own.

1) Code quality is fairly subjective, and in particular novice (very novice) programmers have difficulty rating code. Most professional programmers seem to be able to recognize it though, and feel awe when they come across beautiful code.

2) Code quantity can be misleading, but if you’re on a team and producing a 100-line delta a day, you will notice the odd team member producing 1000-line daily deltas; coupled with even decent ability to tell whether or not that code is maintainable and efficient (in terms of functionality / loc), this is a strong indicator.

3) Actually watching a master write code is fantastic and intimidating. People that code at 60 wpm without even stopping to consider their algorithms, data structures or APIs, but manage at the end of an hour to have a tight, unit-tested, efficient and readable module.

I can think of five people that I know that I would classify as being in discrete levels above me (that is, each of them is distinguishable by me as being either better or worse than the others). I think there are some gaps in there; Jeff Dean is so mindbogglingly skilled that I can’t see anyone on my list ever catching up to him, so there are probably a few levels I don’t have examples for.

datadataeverywhere 12 Sep 2012 11:19 UTC
2 points
in reply to: NancyLebovitz’s comment on: How to deal with someone in a LessWrong meeting being creepy
I like being hugged from behind...by a very small number of people. From everyone else, it’s quite unwanted.

This has had an interesting effect; if someone hugs me from behind, I unconsciously either put them in a bucket of people that I like a great deal, or make myself uncomfortable by telling them “don’t do that”. There’s an odd bit of wiggle room in there, where someone might make me like them more by doing something somewhat uncomfortable to me. If this happened more often, I would take more care to address this particular bias; I also suspect there are subtler variants that I haven’t recognized (I only just realized the above while reflecting on your post).

datadataeverywhere 12 Sep 2012 10:41 UTC
3 points
in reply to: JenniferRM’s comment on: AI timeline predictions: are we getting better?
How many degrees of freedom does your “composition of N theories” theory have? I’m not inclined to guess, since I don’t know how you went about this. I just want to point out that 260 is not many data points; clustering is very likely going to give highly non-reproducible results unless you’re very careful.

datadataeverywhere 22 Oct 2011 12:22 UTC
0 points
in reply to: jhuffman’s comment on: Things you are supposed to like
I agree (have had the same experience), although I argue that mustard, sauerkraut or other bitter/sour foods are better examples than coffee or beer, simply because drugs change the way we process surrounding stimuli.

datadataeverywhere 22 Oct 2011 12:15 UTC
6 points
in reply to: Daniel_Burfoot’s comment on: Things you are supposed to like
This also goes some distance to explaining (in an alternate fashion) why repeated exposure to the artwork increases appreciation for it. Assuming the piece really relies on their exposure to related music, extended exposure forces people to have increasingly similar backgrounds.

datadataeverywhere 17 Oct 2011 17:23 UTC
6 points
in reply to: Hyena’s comment on: [link] SMBC on utilitarianism and vegatarianism.
Torture (not murder) is my stated objection to eating meat.

datadataeverywhere 14 Oct 2011 20:27 UTC
1 point
in reply to: scientism’s comment on: Life is Good, More Life is Better
Funny. I feel the opposite way: I’m okay with dying, but don’t want other people to die.

While I do tend toward suicidal thoughts, even when I’m feeling pretty great the idea of my life continuing is at best of low value. I would hate to die because I know it would hurt lots of people that I’m close to, and I’m also averse to the pain of the process of dying, but nonexistence is generally an attractive concept to me. If I could get away with dying in a manner that didn’t hurt me or others, I probably would.

On the other hand, I would be and have been very pained at the death of others, or even at the thought of them dying. I would react very selfishly to keep people close to me from dying, and attempt to extend that near-mode behavior to far-mode action as well.

datadataeverywhere 13 Oct 2011 21:27 UTC
3 points
in reply to: dreeves’s comment on: Anti-akrasia tool: like stickK.com for data nerds
I’d like to weigh in on this, agreeing with pjeby. I joined beeminder, am enjoying it and expect it to be of great use to me. I don’t care even a little where the money goes. The amount is a penalty to me, and I like the way it is automatically set. If the money allows you to focus more on improving beeminder, that’s great. If it ends up making you rich, that’s just evidence you’re providing a valuable service.

datadataeverywhere 1 Oct 2011 4:46 UTC
1 point
in reply to: Vladimir_Nesov’s comment on: Quixey Engineering Screening Questions
I had thought the solution was very simple before you pointed this out. With some difficulty I improved my solution to O(log(log(n)) * log(n)), and it took quite a bit more time for me to get completely constant sized stack frames.

I suspect most people initially come up with the O(log^2(n)) solution and jump next to the O(log(n)) solution without getting stuck in the middle there, but I’m curious if this gave you any problems.