[1050 TH] BitMinter.com [1% PPLNS,Pays TxFees +MergedMining,Stratum,GBT,vardiff]

[organofcorti]

Here are some figures that I get from the 2nd graph on the rewards page, and from the table on the shifts page.

As I write this, the graph starts at shift 14348, that was on 2013-04-17 11:05 i.e. 15 days ago.

The pool has never quite been lucky since then.

Starting at shift 14670, 2013-04-27 04:23 i.e. about a week ago, the pool has run unlucky, more than I ever saw in the past (but I have only joined about 2 month ago), that is why I asked the question about variance and expected "recovery" time before the actual rewards catch up with the expected ones.

I think that the theoretical, correct answer to the question "how long before we catch up" is: you cannot know when, you can only know that it *will* catch up, at some point. So maybe I should rephrase the question:

From our current "unlucky" status, how long would it take before we have statistically more than 50% chance to catch up with the expected rewards? I believe this question can be (formally) answered. I'm not really expecting it, but if someone is both able and willing to calculate or even approximate it, I would find it useful and appreciate it :-)

Need some figures if I'm going to help - number of blocks in the time period, the number of shares per block, and difficulty of each block. Or I'll do it tonight when I get home.

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[redtwitz]

From our current "unlucky" status, how long would it take before we have statistically more than 50% probability to catch up with the expected rewards? I believe this question can be (formally) answered. I'm not really expecting it, but if someone is both able and willing to calculate or even approximate it, I would find it useful and appreciate it :-)

There will never be more than 50% probability of being lucky, just as there's never more than 50% of probability of being unlucky.

Past luck doesn't affect future luck. It doesn't matter if the pool was lucky or unlucky recently; the probability of finding a block after n times difficulty shares is always the same.

While there's certainly a possibility of evening out the past bad luck or even surpassing the expected rewards in the long haul, this cannot be the likely (p > 0.5) scenario.

My inability to find a simple explanation of why actual payouts have been below expected caused me to move most of my pool work elsewhere.

Luck is just that: luck. There's no explanation for it. You either have bad luck or you don't.

Taking the last 100, 250 and 500 blocks from the statistics, I found that the mean of the required shares to solve a block was 1.216005475, 1.0990548393 and 1.0534418012 times difficulty, respectively.

Assuming a normal distribution and estimating the standard error from the respective samples (0.1262058917, 0.0744550916 and 0.0485402741 respectively), there's a chance of 4.36%, 9.18% and 13.57%, respectively, that a given pool would be that unlucky.

4.36% sounds pretty low, but since there are more than 23 mining pools, chances are that it happens to one of them...

[organofcorti]

Taking the last 100, 250 and 500 blocks from the statistics, I found that the mean of the required shares to solve a block was 1.216005475, 1.0990548393 and 1.0534418012 times difficulty, respectively.

Assuming a normal distribution and estimating the standard error from the respective samples (0.1262058917, 0.0744550916 and 0.0485402741 respectively), there's a chance of 4.36%, 9.18% and 13.57%, respectively, that a given pool would be that unlucky.

4.36% sounds pretty low, but since there are more than 23 mining pools, chances are that it happens to one of them...

Shares per round / D is erlang distributed, so the lower tail CDF for the data you provided (100 @ 1.216005475, 250 @ 1.0990548393, 500 @ 1.0534418012) is 0.9800301, 0.9379993, and 0.8828175 - or 2.00%,  6.20% and 11.72%. So for example, in 100 repeats of 100 blocks, you'd expected to get an average that large or greater 2% of the time. As you say, hardly unusual.

[matt4054]

Luck is just that: luck. There's no explanation for it. You either have bad luck or you don't.

(...)

Assuming a normal distribution and estimating the standard error from the respective samples (0.1262058917, 0.0744550916 and 0.0485402741 respectively), there's a chance of 4.36%, 9.18% and 13.57%, respectively, that a given pool would be that unlucky.

4.36% sounds pretty low, but since there are more than 23 mining pools, chances are that it happens to one of them...

Thanks for your post. It helps me clear things a bit between probability and the normal distribution function. I guess that the fact that luck "is not stateful over time" is counterintuitive to me. Fortunately I'm not gambling ;-)

However, I think PPLNS supporters aren't always very clear about the fact that there is a risk of earning less EVEN IN THE LONG RUN than pure PPS. That's the part that I had missed. Even if one risks just as much losing than winning, the risk is still here compared to PPS. Or am I wrong again?

[organofcorti]

Luck is just that: luck. There's no explanation for it. You either have bad luck or you don't.

(...)

Assuming a normal distribution and estimating the standard error from the respective samples (0.1262058917, 0.0744550916 and 0.0485402741 respectively), there's a chance of 4.36%, 9.18% and 13.57%, respectively, that a given pool would be that unlucky.

4.36% sounds pretty low, but since there are more than 23 mining pools, chances are that it happens to one of them...

Thanks for your post. It helps me clear things a bit between probability and the normal distribution function. I guess that the fact that luck "is not stateful over time" is counterintuitive to me. Fortunately I'm not gambling ;-)

It may have sounded counterintuitive because redtwitz was assuming a normal distribution in a situation where that assumption can't be made without significant loss of accuracy.

However, I think PPLNS supporters aren't always very clear about the fact that there is a risk of earning less EVEN IN THE LONG RUN than pure PPS. That's the part that I had missed. Even if one risks just as much losing than winning, the risk is still here compared to PPS. Or am I wrong again?

If a PPLNS pool has lower fees than a PPS pool, then eventually then probability that you earn more on a PPLNS pool will approach 1.0 over time.

[organofcorti]

Luck is a factor for days, or even weeks.  I am talking about months of below expected results.

And luck is bi-directional.  Except for Bitminter where the payout graph hasn't gone over the expect line for more than a year.

Put that in your probability calculator and write a little lecture about it.

I do pool audits for US$120 (1.29 btc). PM me if you'r really interesting in knowing for sure if there's a problem or not.

[jamesg]

Another explanation is that some party is conducting a block withholding attack on the pool.  That is:

They direct hashpower at the pool but modify their mining software to not submit shares with a target value greater than X where X is less than the current difficulty.

The result is that they collect coins without every contributing to the pool. 

Such a strategy would be a very viable attack on competing pools.

I can think of several easy mechanisms to address such an attack, but I doubt that any pools do so today.

This is patently false. Please think about what you are saying before you start typing such things.

There is no way to perform a MITM attack or block withholding attack where the miner withholding receives the coins instead of the pool.

[gyverlb]

Another explanation is that some party is conducting a block withholding attack on the pool.  That is:

They direct hashpower at the pool but modify their mining software to not submit shares with a target value greater than X where X is less than the current difficulty.

The result is that they collect coins without every contributing to the pool. 

Such a strategy would be a very viable attack on competing pools.

I can think of several easy mechanisms to address such an attack, but I doubt that any pools do so today.

This is patently false. Please think about what you are saying before you start typing such things.

There is no way to perform a MITM attack or block withholding attack where the miner withholding receives the coins instead of the pool.

This is not what he wrote about. The coins received are not the coins from the withholded blocks but the coins from the usual payout (for share submission).

[Epoch]

Another explanation is that some party is conducting a block withholding attack on the pool.  That is:

They direct hashpower at the pool but modify their mining software to not submit shares with a target value greater than X where X is less than the current difficulty.
The result is that they collect coins without every contributing to the pool.  
Such a strategy would be a very viable attack on competing pools.
I can think of several easy mechanisms to address such an attack, but I doubt that any pools do so today.

This is patently false. Please think about what you are saying before you start typing such things.
There is no way to perform a MITM attack or block withholding attack where the miner withholding receives the coins instead of the pool.

I thought Entropy-uc's post was pretty clear, and mentions nothing about a Man-In-The-Middle attack. Let's put it this way:

1) I direct my hashpower at a pool.
2) when my (custom) mining software detects that I have found a block, it does not submit it.
3) when someone else finds a block at the pool, I get paid my share just like all the other miners.

So, I have contributed nothing (and never will), I have performed a 'block withholding attack', and I still get coins. Granted, there is no direct benefit to me by doing this (and even my rewards are lower because of it). But if I point enough hashpower at the pool, it is possible to 'discredit' the pool's rep by imposing what appears to be an ongoing (and perhaps never-ending) run of bad luck because of my block withholding attack.

I'm not suggesting this is what is happening. I merely point out that I don't see anything 'patently false' about Entropy-uc's post.

[WhitePhantom]

Another explanation is that some party is conducting a block withholding attack on the pool.  That is:

They direct hashpower at the pool but modify their mining software to not submit shares with a target value greater than X where X is less than the current difficulty.
The result is that they collect coins without every contributing to the pool. 
Such a strategy would be a very viable attack on competing pools.
I can think of several easy mechanisms to address such an attack, but I doubt that any pools do so today.

This is patently false. Please think about what you are saying before you start typing such things.
There is no way to perform a MITM attack or block withholding attack where the miner withholding receives the coins instead of the pool.

I thought Entropy-uc's post was pretty clear, and mentions nothing about a Man-In-The-Middle attack. Let's put it this way:

1) I direct my hashpower at a pool.
2) when my (custom) mining software detects that I have found a block, it does not submit it.
3) when someone else finds a block at the pool, I get paid my share just like all the other miners.

So, I have contributed nothing (and never will), I have performed a 'block withholding attack', and I still get coins. Granted, there is no direct benefit to me by doing this (and even my rewards are lower because of it). But if I point enough hashpower at the pool, it is possible to 'discredit' the pool's rep by imposing what appears to be an ongoing (and perhaps never-ending) run of bad luck because of my block withholding attack.

I'm not suggesting this is what is happening. I merely point out that I don't see anything 'patently false' about Entroy-uc's post.

Thank you.  I don't have any reason to know it is happening either.

But it is a possible attack, there are people with motive to conduct such an attack, and there is enough misfortune appearing for many different pools lately to move my threat indicator from 'coincidence' to 'enemy action'.

Perhaps an analysis should be done on whether any high hash users are finding no blocks for the pool or perhaps far fewer blocks than is statistically likely.

[FanDjangoBTC]

Speculations on the motive of such an attack, only destruction if no personal profit possible?

[Rishodi]

Luck is a factor for days, or even weeks.  I am talking about months of below expected results.

And luck is bi-directional.  Except for Bitminter where the payout graph hasn't gone over the expect line for more than a year.

Where are you getting that information? The payout graph that I see, on Bitminter's rewards page, only shows the last few weeks, although that is not clear as the scale of the horizontal axis is not labeled.

Perhaps an analysis should be done on whether any high hash users are finding no blocks for the pool or perhaps far fewer blocks than is statistically likely.

With access to the pool's DB, that sort of analysis would be easy to do and would quickly identify any power users who had submitted a large number of shares but not found any blocks. However, if this type of withholding attack were indeed occurring, such analysis would easily miss a distributed attack of the same sort.

For example, if a user with 500GH/s has been mining for months, has submitted hundreds of millions of shares, and has yet found no blocks, that might be suspicious. But if 500 users with 1GH/s each had been mining for the same period of time and collectively submitted the same number of shares, it is entirely likely, on a per-user basis, that each of them would not have found a block. Thus if there were a large number of users participating in such an attack, at lower hashing speeds it would be essentially impossible to distinguish the miners who were participating in it from those who were not.

That being said, since there is no profit motive in such an attack -- worse, it's actually detrimental for any pool user to withhold a block hash which meets the target difficulty -- I think that such an attack is rather unlikely. The motive would perhaps be personal or spiteful in nature, and it would likely not be sustained for long due to opposing financial motivations.

[kano]

Speculations on the motive of such an attack, only destruction if no personal profit possible?

With PPS, the loss for the miner is only 1 share each time he finds a block ...
Thus on PPS it will directly affect the pool op but the miners are not affected at all and the witholder is losing only 1 in "network difficulty"/"work difficulty" shares ...
i.e. 10million/"work difficulty" (so mining at 10 diff the miner loses 0.0001% ...)

[organofcorti]

[...]
I DO NOT suspect malfeasance on the operator's part at all - if Dr. Haribo was cheating, why not keep NMC payouts all to himself?  (I wouldn't be surprised to find that some pools are merged mining and keeping the alt-chain coins)

I suspect there is either a significant bug in the pool, or someone has worked out a method to exploit the payout mechanism similar to the hopping strategy.  Or it could be as simple as a bad calculation in the expected vs. actual payouts graph.

To work out what is going on would require detailed analysis of data that only the pool has access to.  [....]

No, you're assuming too much there. All the charts you are looking at are based on publicly available data, so the answer is in the data.

It's non-trivial but quite possible to analyse that data and determine 1. if the data is extremely unusual, and 2. hypothesize about reasons for any data anomaly. I've done exactly that here:

http://organofcorti.blogspot.com.au/2012/10/81-bitcoinpool-another-bitclockers.html
http://organofcorti.blogspot.com.au/2013/01/82-bitcoinpool-great-anomaly-hunt.html

Without analysing data you're flying in the dark and just guessing at problems without knowing if there are any significant problems, or what the nature of the problems are.

If you do wish to put your money where your mouth is, the offer holds

[PCMiner]

Someone with access to several ASIC's is onboard now, cranking 1.5+THps?  That's insane.  I'll leave my token Nvidia machines on BTC, but the end is near for all GPU BTC mining.  Time for me to switch most everything over to LTC.

[Newar]

Someone with access to several ASIC's is onboard now, cranking 1.5+THps?  That's insane.  I'll leave my token Nvidia machines on BTC, but the end is near for all GPU BTC mining.  Time for me to switch most everything over to LTC.

ASICMINER

Another 1.5T online, temporarily allocated on bitminter. Will switch to solo later on.

[Jcw188]

Someone with access to several ASIC's is onboard now, cranking 1.5+THps?  That's insane.  I'll leave my token Nvidia machines on BTC, but the end is near for all GPU BTC mining.  Time for me to switch most everything over to LTC.

ASICMINER

Another 1.5T online, temporarily allocated on bitminter. Will switch to solo later on.

Ah I was wondering why my expected btc per block found went down substantially. This would explain it right?  Weird though, not like we have been finding many blocks lately :-(

[organofcorti]

Someone with access to several ASIC's is onboard now, cranking 1.5+THps?  That's insane.  I'll leave my token Nvidia machines on BTC, but the end is near for all GPU BTC mining.  Time for me to switch most everything over to LTC.

ASICMINER

Another 1.5T online, temporarily allocated on bitminter. Will switch to solo later on.

Ah I was wondering why my expected btc per block found went down substantially. This would explain it right?  Weird though, not like we have been finding many blocks lately :-(

You get less btc per block and more blocks. btc per shift is unaffected, except that variance is reduced.

[matt4054]

'realasicminer' has just found its first block, let's hope this was just bad luck and things go back to normal.

I like BitMinter (that's why I elected it as primary pool), but I must admit that:

• I had the impression that BitMinter was REALLY unlucky for the past 2 weeks,
• As one user out of thousands, I'm not willing to pay >1BTC on my expenses to find out why some pool would have a problem (and not getting ROI), I think the pool operator should do it on pool fee's expenses, now that the fees are in place (with all due repect the DrHaribo's work),
• Switching pools (and losing the NMC) seems to make more sense for an individual, GPU miner. The end is near anyway.

[GuiltySpark343]

Now with 8+ TH/s we should on avg be finding 16 blocks/day at current difficulty 10076293.

So far today (past 15 hrs) found 4.
Yesterday (during full 24 hr period) found 7.