Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Hello, World

m.whitehouse.gov

Post reply on HN
Print view View original

71–80 of 121 posts

Re: Hello, World

#71

Post by mappu »

javert wrote: post #62
mappu wrote: post #54

Earlier quoted context omitted.

Most "free" markets don't have perfect competition, nor perfect information, nor rational actors. It's possible for Microsoft to provide a terrible service and for no better competitors to emerge. Consider last-mile telephone lines. It's wasteful to have ten companies each spend billions of dollars digging up the same roads to lay the same cables - and it's a nearly-impossible barrier to entry for new competitors. Su…

There's an easy solution to the last-mile problem, which is for communities to own the infrastructure and operate it as a non-profit. Believe me, people would do that if they were getting sufficiently screwed by telcos and if it were legal. Actually, the former condition is already satisfied, but the latter is (basically) not. Though there have been lots of municipal broadband efforts, which is a point in my favor, h…

The solution is for the lines to be operated prioritizing the community before profit, yes. We've agreed on the fundamentals but now differ in imagination of the size of the community.

Why not extend such egality to all citizens? And why do people have to get "screwed by telcos" first before it can happen?

Re: Hello, World

#72

Post by jamespo »

javert wrote: post #61
marvy wrote: post #55

Earlier quoted context omitted.

Ok, I've read it. I agree it is serious. But I think it's also wrong. Monopolies can be abused in ways that make it almost impossible to compete against them. Let's use Windows as an example. Some companies that sell Windows boxes also sell Linux boxes. (Dell for example.) Of course, the Linux boxes are less popular. But why not sell a computer that can dual boot? People would be a lot more willing to experiment with…

If Windows started sucking, people would switch. Demand would arise for a better alternative. In the long run, companies and consumers are not going to choose a significantly inferior product. There are no specific examples that will get you out of this. Actually, it Windows already kinda does suck, which is why so many people (even companies) use Apple. And there are lots of other alternative OSs.

Unfortunately the example given and the "windows tax" is a perfect example. Microsoft had such size and control over the industry they could strangle competitors at birth. Who knows what they would have done without this tiresome legislation.

Re: Hello, World

#73

Post by Toenex »

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

Thank you Professor Falkener. Now how about Alice and Bob play Global Thermonuclear War?

Re: Hello, World

#74

Post by blumkvist »

javert wrote: post #61
marvy wrote: post #55

Earlier quoted context omitted.

Ok, I've read it. I agree it is serious. But I think it's also wrong. Monopolies can be abused in ways that make it almost impossible to compete against them. Let's use Windows as an example. Some companies that sell Windows boxes also sell Linux boxes. (Dell for example.) Of course, the Linux boxes are less popular. But why not sell a computer that can dual boot? People would be a lot more willing to experiment with…

If Windows started sucking, people would switch. Demand would arise for a better alternative. In the long run, companies and consumers are not going to choose a significantly inferior product. There are no specific examples that will get you out of this. Actually, it Windows already kinda does suck, which is why so many people (even companies) use Apple. And there are lots of other alternative OSs.

So according to you, it's alright for a company to hold a monopoly position and erase their competitors, as long as they provide the bare minimum its customers need?

Re: Hello, World

#75

Post by philh »

praptak wrote: post #69
rjtobin wrote: post #13

Some discrete mathematicians are interested in this sort of problem, which they call "simultaneous hat guessing". There are quite a few papers, in case anyone is interested and unfamiliar with this sort of thing. Another fun problem, probably better known, is sequential hat guessing: take 100 people in a line, arranged so that each person can see everyone in front of them, but no-one can see any of the people behind…

An actual fun problem: 100 prisoners are each assigned a black or white hat, at random. As always, they cannot communicate after the hats are assigned. Then they are shown each other. None sees own hat, everyone sees everyone elses hat. Then they are led into separate rooms and each guesses their own hat color. They win only if everybody guesses correctly. What strategy maximizes the probability of that event?

Gurl pna trg svsgl creprag ol rirelbar thrffvat fhpu gung gur ahzore bs oynpx ungf vf rira (be bqq).

I wouldn't be surprised if this is optimal, but I also wouldn't be surprised if it's not.

Re: Hello, World

#76

Post by [deleted] »

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

[deleted]

Re: Hello, World

#77

Post by antimagic »

furyofantares wrote: post #5
SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

My experience arriving at this solution made me a bit curious as to how others solved it. Was there reasoning involved before you arrived at a strategy and verified it, or did the strategy just come to you? Did you try multiple strategies, and if so, was there a method to generating/iterating on them, or were they just coming to you and you tried them?

I personally just worked through a concrete example. So Alice flips her coin and gets heads. I then just assume that she is going to guess the opposite of what she flipped, so she guesses tails.

For Alice to lose, Bob would have to have flipped heads. Now Bob knows, because he has discussed strategy with Alice prior to doing the flips that either Alice flipped tails, in which case she has won, or she has flipped heads, in which case she has lost. But Bob can then bet on heads, in which case he knows that he wins if Alice loses.

That was my way of reasoning things anyhow. As you can see from the other responses, there are many different ways of arriving at the right answer.

Re: Hello, World

#78

Post by yorkyorkyork »

SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

Easier explenation There are 16 possibilities

   A Alice's coin
   Ac Alice's choice
   B  Ben's coin
   Bc Ben's choice
They win if A's and Bc's OR B's and Ac's are the same

   A Ac B Bc
   T T  T T  W  
   H T  T T  W
   T H  T T  W
   H H  T T  L
   T T  H T  W
   H T  H T  L
   T H  H T  W
   H H  H T  W
   T T  T H  W
   H T  T H  W
   T H  T H  L
   H H  T H  W
   T T  H H  L
   H T  H H  W
   T H  H H  W
   H H  H H  W
It's easier to check for when they are losing:

   A Ac B Bc
   H H  T T |they both stick to their choices
   H T  H T |they both flip
   T H  T H |they both flip
   T T  H H |they stick
So the winning strategy is if one of them sticks to his choice and other flips it's choice.

Re: Hello, World

#79

Post by darkonmist »

yorkyorkyork wrote: post #78
SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

Easier explenation There are 16 possibilities A Alice's coin Ac Alice's choice B Ben's coin Bc Ben's choice They win if A's and Bc's OR B's and Ac's are the same A Ac B Bc T T T T W H T T T W T H T T W H H T T L T T H T W H T H T L T H H T W H H H T W T T T H W H T T H W T H T H L H H T H W T T H H L H T H H W T H H H W H H H H W It's easier to check for when they are losing: A Ac B Bc H H T T |they both stick to the…

Wow, that is way better explanation to check on where they may lose. Thanks!

Re: Hello, World

#80

Post by sgreben »

furyofantares wrote: post #5
SMackinnon wrote: post #3

Spoiler: Bob always chooses the same as his flip, Alice always chooses the opposite of her flip. B A H H - Bob chooses heads, Win H T - Alice chooses heads, Win T H - Alice chooses tails, Win T T - Bob chooses tails, Win

My experience arriving at this solution made me a bit curious as to how others solved it. Was there reasoning involved before you arrived at a strategy and verified it, or did the strategy just come to you? Did you try multiple strategies, and if so, was there a method to generating/iterating on them, or were they just coming to you and you tried them?

Purely mechanically. Just writing down the problem statement we get:

    \exists f,g: \forall a,b: (f(b)=a) | (g(a)=b)
where f,g are the guesses and a,b are the flips. Each guess is a function of the information available to the respective player -- the outcome of his own coin flip. There's only 4 unary boolean functions:

    f,g \in {true,false,id,not}
The constant functions are out and order doesn't matter, so we're left with

    {(id,not),(id,id),(not,not)}
Here I just tried (id,not) first, but 3 choices are easy to check exhaustively.
Post reply on HN