jeffcoat

We can only guess about what's going wrong for you specifically . But I like guessing:

(extremely mild spoilers:)

- A core skill for Nethack is understanding how much danger you're in at any particular moment. Your comment about soldier ants below tells me you've made good progress here. But you need to recognize when you're in danger and how long you have to deal with that problem before you'll react appropriately.

- Nethack's dungeon isn't linear, it branches. (Think of the gnomish mines here, but there are other examples deeper.) When you're getting in over your head in one branch, go back up the stairs and switch to another one.

- When you're in immediate danger, Stop. Look through your inventory, consider your options. Think especially about wands, think about ways to write Elbereth, think about scrolls. Think about ways to use diagonal movement to your advantage to get to an escape, or a more defensible position. You have all the time in the world to think. There may not be a solution, but I've died more than a few times with more than one thing in my inventory that could have saved me.

- You need to be able to identify some things without waiting for a scroll of identify to fall into your lap. Price is the easiest way to identify the scroll of identify itself. It's also straightforward to learn to identify most useful wands: with spoilers or by experimenting. Engraving with the wand will often give you more information than zapping it. A lot of your early I'm In Danger toolkit will come from wands you've identified this way.

Good luck, have fun.

(Intermediate player, a few dozen ascensions 20 years ago.)

Even switching from magnetic to true is unhelpful close enough to the South pole. All directions are north.

We have to switch to "grid" north to make sense of directions there.

https://en.wikipedia.org/wiki/Universal_polar_stereographic_...

This is amazing. Thank you.

Probably not. Knowing the speed-of-light round trip time to a network location gives you a bound on how much you can improve the performance of remote operations.

For example, I'm in Austin, querying a database hosted in Amazon's us-east-1 data center ("Northern Virginia"). Call it 1000 miles away, 2000 mile round trip.

    You have: 2000 miles
    You want: millilightseconds
            2000 miles = 10.736388 millilightseconds

  MCMLXVII + LXV
   = MCCCCCCCCCLXVII + LXV (canonicalize)
   = MCCCCCCCCCLXVIILXV    (concatenate)
   = MCCCCCCCCCLLXXVVII    (sort)
   = MCCCCCCCCCLLXXXII     (combine, VV => X)
   = MCCCCCCCCCCXXXII      (... keep combining, LL => C)
   = MMXXXII               (... C{10} => M, nothing left to combine)
   = MMXXXII               (optionally, look for ways to re-write with the subtraction rule)

I choose to believe it's a prophecy, foretelling the coming of a Universal search engine that will someday make that joke stop working.

You're right, thank you.

You're recalling a different incident: engine-out problems are a routine part of flight training at every level.

You're thinking of https://en.wikipedia.org/wiki/United_Airlines_Flight_232

where so much of the plane broke that they had to invent a new way to fly it.

I can't turn up a reference right now, but like you say, in the next few years that failure was repeatedly simulated, and all the simulated planes crashed.

(IIRC, Haynes declined to try his hand at any of the simulations, explaining that the one time when it really mattered was enough for him.)

Certified Programming with Dependent Types

http://adam.chlipala.net/cpdt/

You'll also need to know that e^x = sum{0 -> infinity} x^n / n!.

Not so stupid: Start with the phrase "Hoteling's rule" for a century of academic analysis of that question.

If you own an oil field, you have to balance a number of factors:

* How is the price of oil changing, relative to overall inflation? You mentioned this one.

But also,

* Are technological improvements (either increasing the total amount of extractable oil in the world, or outright oil replacements) going to dramatically lower the price if I wait too long?

* Is it still going to be my oil next year, or am I going to be first against the wall when the next revolution comes?

My (unsophisticated, outsider) opinion is that if you see oil-producing countries selling as quickly as they can, that's weak evidence that they're worried about the last two bullets.

I enjoyed it: not a sports fan, knew little of baseball except that the one game pro game I've seen in person was super-boring [to me].

_Moneyball_ isn't about baseball so much as it's about how easy it is for humans to be tricked by our intuitions and habits. Moneyball talks about baseball from the point of view of someone who everyone just assumed would be good -- and wasn't -- as he's trying to make more and more objective assessments of players, and wielding his conclusions against competing, more traditional managers.

It's because "latitude lines" aren't really lines in this context (except the one at the equator).

If you took two points from one of those latitude "lines", you'd always be able to find a shorter path between them than the path along the latitude. If you take the shortest path between the two points and extend it all the way around the sphere, you'll end up with a great circle. That great circle is an actual "line" in this geometry.

https://en.wikipedia.org/wiki/Spherical_geometry

It's obvious that moving oil in space helps, right? You move the resource from a place it's relatively plentiful to a different place where oil is relatively scarce. Say, from the Persian Gulf to Australia.

The same thing is happening here:

These ships are trying to move oil from a time when oil is relatively plentiful to a time when it's relatively scarce. It's riskier, but if they succeed, everybody wins: they make money, and they do it by lessening that future scarcity.

All of this is fine for real-valued inputs and outcomes. It's the number of events (coin flips, measurements, etc) that we're restricting to be countable.

I think I know what you're getting at, but the problem here is that prosecutors have some discretion.

The chain of thought that goes

  I only prosecute worthy cases

  => I picked those cases because these people are guilty,
      and need to be convicted for the good of society 

  => my conviction rate is exactly the same as my 
     'I made a better world' rate.

ABC ran pretty much this same story in 2010:

http://abcnews.go.com/Blotter/loaded-gun-slips-past-tsa-scre...

  According to one report, undercover TSA agents
  testing security at a Newark airport terminal on
  one day in 2006 found that TSA screeners failed
  to detect concealed bombs and guns 20 out of 22 times.

  A 2007 government audit leaked to USA Today revealed
  that undercover agents were successful slipping simulated
  explosives and bomb parts through Los Angeles's LAX
  airport in 50 out of 70 attempts, and at Chicago's
  O'Hare airport agents made 75 attempts and succeeded
  in getting through undetected 45 times.

The slides are interesting enough that I went looking to see if the actual talk that goes with them was online anywhere; found it at

http://chariotsolutions.com/screencast/philly-ete-2015-7-mon...

It's tough being smart and influential: your [Dijkstra's] successes and mistakes end up going through the same megaphone.

I was in a 1 or 2-person office while I was at IBM. Their policy (at that branch) was a private office for senior developers and up, two to an office otherwise.

I'm at Motive right now; the large majority of developers here have their own office. (And we're hiring: developers and testers, no telecom experience necessary, mostly in Austin, TX.)

You're probably thinking of Isaac Asimov's story "My Son, the Physicist".

http://en.wikipedia.org/wiki/My_Son,_the_Physicist

Did you see the first line? "That mathematics is thought to be consistent justifies the use of Proof by Contradiction." So the original author agrees with you.

You're right too, though: most of the value of that post is in the first paragraph, which is a very concise presentation of an interesting (apparent) paradox.

Wikipedia presents both origin stories, but the accounting version (black ink) does appear to be a 1980s back-formation trying to put a nicer spin on the name.

http://en.wikipedia.org/wiki/Black_Friday_(shopping)#Origin_...

Great demo.

The last question, where I had to name and spell the part, caught me by surprise -- the difficultly level had, up until then, been increasing very slowly, and that felt like a huge jump.

Wishlist feature: Speech recognition, in the sense of having to name a part out loud.

That borders on impressive: Four of the five statements leading into the "proofs" are wrong (and the fifth needs a lot of charity), and all three of the proofs are meaningless in exactly the same way.

I picked up Venkatesh's book _Gang Leader for a Day_ on the strength of the work cited here ... and ended up throwing it out.

He's not an economist: he has a very clear idea of which jobs are useful in a society and which jobs aren't, and no interest at all in what the market has to say.

I'm sure he has useful data, but everything he writes goes through that filter, and there's no way to trust what he says about people dealing drugs, because he makes it so clear that everyone doing anything outside the law is Evil, and so everything they do is tainted.

It's a fine combination; as the settings hint, they were designed to be used together.

The XML spec refers to them as "empty-element" tags.

http://www.w3.org/TR/REC-xml/#sec-starttags

We say an algorithm is in P if the running time grows as a polynomial function (e.g., n^2, but not 2^n) of the input size (n, in my example; the number of variables in the polynomial in this paper).

We say that an algorithm is in NP if checking a given solution can be done in polynomial time. For example, if the problem is to find a path that visits all the nodes of a graph (or cities on a salesman's route, or whatever) exactly once that's less than some distance k, you might have to try every possible route to find a solution, but given an answer, you can check it's distance and compare it to k very quickly.

NP-hard means (even more informally than the above) that the problem is "at least as hard as the hardest problem in NP". (Some problems in NP are easy; e.g., if you have an algorithm in P to find a solution to a problem, then you can obviously also check a given answer in polynomial time.)

It is not known whether or not all problems for which answers can be checked in polynomial time (NP) can also be solved in polynomial time (P).

They're saying that if P=NP, there does exist an algorithm in P that can decide the convexity of a degree 4 polynomial (even though they don't know what that algorithm is right now), and if P!=NP, then there doesn't.

(*Edit: The last paragraph is wrong:

I can't find that they've proven that the determining convexity is in NP, just that it's NP-hard and they didn't rule out it being in NP. (Recall that some NP-hard problems are not in NP; halting problem is one.)

So it's possible that that both P=NP and there's still no algorithm in P that can check convexity. But if P!=NP, that algorithm definitely doesn't exist.

Also, on closer reading, the relevant "size" of a problem that this paper is talking about (n) is the number of bits needed to represent the coefficients of the polynomial.)

I didn't mean to defend the idea that every fact is true for a reason.

I remember reading something of Chaitin's a couple of years ago that drove home the point that most mathematical facts are, in some fairly-well defined sense, true for no reason at all.

(Alas, I don't remember the argument well enough to re-cap it here.)