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

Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

r6.ca

Post reply on HN
Print view View original

81–90 of 128 posts

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#81

Post by gowld »

meuk wrote: post #74

I have been thinking about this as well, in another context. When I am at the tennis court, I always seem to be surrounded by players which are far above average. This seems paradoxical, but you're more likely to meet the players which train most often, and they are also most likely to be the best tennis players.

It's also the reason why most people are less popular than their average friend is, even though they are (on average) as popular as the average person! Since popular people are on everyone's friend list, but unpopular people are only on a few friend lists, your friend list is biased toward popular people.

Mathematical explanation of why Facebook makes you depressed.

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#82

Post by foota »

travisjungroth wrote: post #45
foota wrote: post #39

Earlier quoted context omitted.

Wouldn't cross wind cancel out in average though? (even though head and tail winds don't)

No, because you spend some of your forward speed flying into the wind to keep the desired ground track. Imagine an airplane that flies 100mph. You want to fly north, but you have a 90pmh crosswind from the east. You have to point almost directly into the wind just to keep from getting blown off course. You can turn a little to the north, and you'll go very slowly. If you instead have the wind come from the east, you…

Sure, with a consistent cross wind of course you'll have to spend energy fighting it, but if you don't fight it and halfway it changes, you'll end up at your destination in the same time as you would have otherwise, no?

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#83

Post by taejo »

tvladeck wrote: post #62

> Correct, that is exactly what I am saying. If you pick a random point in time, you expect 20 minutes between the previous block and the next block on average. I thought this sounded funny, and I did a little simulation to see if it was correct. Given his assumptions (poisson with lambda 10), you do not get that answer. I got right around 10, which is what I would expect. https://gist.github.com/tvladeck/e7a164dfe70…

You've made the exact mistake the article is talking about. You're weighting all blocks equally, but at any moment the current block is more likely to be one that was the current block for a long time.

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#84

Post by gowld »

rusbus wrote: post #29

TLDR: Since blocks that take a long time to mine fill up more wall-clock time, if you pick an arbitrary instant of wall clock time, you're more likely to be in a "slow" block than a fast block. Specifically, you expect to wait 2x the average.

That's not correct. That's the opposite of the correct reason.

Consider a simple (not-exactly-Poisson) set of blocks: 20x1minute intervals, plus 1x10minute interval. The average interval size is (20x1min + 1x10min)/21 = ~1.4min

A random moment in time is twice as likely to be in a fast blocks as in the slow blocks.

But average wait time (given a uniformly random start times) is (20min0.5min + 10min 10min)/30min = 110min^2/30min = ~3.6min.

That per-start-instant average wait time is longer NOT because you are more likely to be in a slow block, but because being in a slow block has a much longer average wait-time than being in any of the fast blocks.

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#85

Post by gowld »

marmaglade wrote: post #30

The hitchhiker's paradox is correct, taking a point and looking backward or forward will correctly give an average event 10 minutes away, but combining the events to give an average of 20 minutes is false. Two events have been chosen resulting in a conditional probability. Put more clearly, an event happens on average 10 minutes in the past, but using the same starting point for the event in the future links the even…

This is simply incorrect, and the (hypothetical) burden is on you to disprove the theoretical and empirical results that have been shown to prove the solution.

The conditional probability is equal to the unconditional probability, specifically because the Poisson model (which Bitcoin hashing approximates) is a model of fully independent events.

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#86

Post by aidenn0 »

foota wrote: post #82
travisjungroth wrote: post #45

Earlier quoted context omitted.

No, because you spend some of your forward speed flying into the wind to keep the desired ground track. Imagine an airplane that flies 100mph. You want to fly north, but you have a 90pmh crosswind from the east. You have to point almost directly into the wind just to keep from getting blown off course. You can turn a little to the north, and you'll go very slowly. If you instead have the wind come from the east, you…

Sure, with a consistent cross wind of course you'll have to spend energy fighting it, but if you don't fight it and halfway it changes, you'll end up at your destination in the same time as you would have otherwise, no?

Sure; if you can predict the future, and the future happens to be that the crosswindws will oppose each other, then you can just set your heading and get there.

However, if the wind doesn't shift you are now taking even longer to get there because you'll have to turn to go straight upwind once your destination is directly upwind from you.

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#87

Post by pjc50 »

modeless wrote: post #79
dmitriid wrote: post #71

Earlier quoted context omitted.

> but often anti-blockchain This is precisely because of: "The upvoted stories, the comments, the discussion are of such a high quality. It's just the best resource to stay informed and educated in tech." If the best, the brightest, the most educated are anti-blockchain, there are definitely reasons for them to be. --- BTW. Is this true what the article is saying: it takes 10 minutes for a transaction to clear in bit…

Yes, it takes 10 minutes on average for a transaction to be included in a block. Potentially much longer if you are unlucky or didn't pay a high enough fee. On top of that most places won't accept just one block. The standard is 6 blocks, so 1 hour on average. That's the price you pay for a truly trustless distributed system. Still (much) faster than ACH or wire transfers or securities trade settlement.

.. but slower than contactless or other card transactions, and (usually) slower than Faster Payments.

(Comparing to securities settlement is interesting, because cryptocurrency exchanges use off-blockchain "settlement" within themselves. Trades execute near-instantly because they're just updating a database. However, settling your money out of an exchange can take a lot longer)

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#88

Post by bkor »

modeless wrote: post #79
dmitriid wrote: post #71

Earlier quoted context omitted.

> but often anti-blockchain This is precisely because of: "The upvoted stories, the comments, the discussion are of such a high quality. It's just the best resource to stay informed and educated in tech." If the best, the brightest, the most educated are anti-blockchain, there are definitely reasons for them to be. --- BTW. Is this true what the article is saying: it takes 10 minutes for a transaction to clear in bit…

Yes, it takes 10 minutes on average for a transaction to be included in a block. Potentially much longer if you are unlucky or didn't pay a high enough fee. On top of that most places won't accept just one block. The standard is 6 blocks, so 1 hour on average. That's the price you pay for a truly trustless distributed system. Still (much) faster than ACH or wire transfers or securities trade settlement.

SEPA instant will settle transactions 10 seconds. Drawbacks: banks can opt to participate, initially limited to 15k EUR, plus not obvious what the cost is. Banks are charged 1 EUR per transaction, so it'll be at least 1 EUR charged to customers.

The price of a transaction is as important as the speed, IMO.

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#89

Post by [deleted] »

gowld wrote: post #84
rusbus wrote: post #29

TLDR: Since blocks that take a long time to mine fill up more wall-clock time, if you pick an arbitrary instant of wall clock time, you're more likely to be in a "slow" block than a fast block. Specifically, you expect to wait 2x the average.

That's not correct. That's the opposite of the correct reason. Consider a simple (not-exactly-Poisson) set of blocks: 20x1minute intervals, plus 1x10minute interval. The average interval size is (20x1min + 1x10min)/21 = ~1.4min A random moment in time is twice as likely to be in a fast blocks as in the slow blocks. But average wait time (given a uniformly random start times) is (20min 0.5min + 10min 10min)/30min = 11…

[deleted]

Re: Why Is It Taking 20 Minutes to Mine This Bitcoin Block?

#90

Post by [deleted] »

quickthrower2 wrote: post #69
rusbus wrote: post #29

TLDR: Since blocks that take a long time to mine fill up more wall-clock time, if you pick an arbitrary instant of wall clock time, you're more likely to be in a "slow" block than a fast block. Specifically, you expect to wait 2x the average.

Ha that's why I spend most of my driving time stuck in traffic. And why do 3 buses come at once? Because the first one takes all the passengers, so stops more and gets slowed down. The other 2 catch up. And also if you do half your trip and 10mph and the other at 20mph your average isn't 15mph. You spent more time at 10mph!

[deleted]
Post reply on HN