4 ms·

How do you calculate the hash rate? I have spent some time trying to understand the various hash rate estimates people come up with. Basically, I've determined

How do you calculate the hash rate? I have spent some time trying to understand the various hash rate estimates people come up with. Basically, I've determined that they're all 100% bogus. People like to work from the difficulty using bad/incorrect statistics since that's the most obvious way to get to something in the units of hashes/s, but I can never understand exactly what the process is. I'm genuinely curious to know what people do in practice, since I'm genuinely curious to know the "real" answer.

maxerickson 14y ago
The network collaborates to adjust the mining difficulty, to keep the rate of new coins approximately the same over time: https://en.bitcoin.it/wiki/Difficulty https://en.bitcoin.it/wiki/Difficulty There is a linear relationship between the hash rate and the difficulty (there is further discussion at that link).
- deepblueocean 14y ago
  I'm aware of that. rwinn, can you tell me if this is what you're doing? It's in your last sentence that you go wrong. There's a relationship between the number of expected hashes per new block and the difficulty. That tells you something about the hash rate, but not the rate itself. Actually, it tells you something about the number of unique hashes being tried per new block (in expectation). And for some applications, that may, in fact, be what you care about. Specifically, the appearance of new blocks is, if you like, a random variable with an exponential distribution. You can, in principle, estimate the rate parameter for this distribution using the difficulty and the timestamps in the Bitcoin log, but it's not straightforward. The last time I got into it, I was halfway through building a Bayesian estimator for the rate parameter using the log before I had to give up and move on to real work. I'll do it soon.
  - maxerickson 14y ago
    I don't see how a hash (as a token of bitcoin work) would be anything other than unique (for the result to be useful to me it has to include my address in the input). In what applications would the likely immediate hash rate be more useful than the historical average hash rate? I guess the obvious one is turning some bit of mining hardware on and off.
gibybo 14y ago
100% bogus? I'm not sure what bad/incorrect statistics you are referring to since it's relatively straight forward to find. The current target hash is "0x000000000000022FBE0000000000000000000000000000000000000000000000" This means that to solve a block, you must find a SHA-256 hash of that block's transactions + nonce that hash to a value equal or below that target. Since the output of a SHA-256 hash is essentially random, the probability of finding a nonce that evaluates to hash at or below that target is roughly [target]/[possible sha256 outputs] or 3.51e60/2^256, or 3.034e-17. On average, that means it takes 1/3e-17 or 3.3e16 hashes per block. To calculate average hashes per second of the network, we look at number of blocks solved in the last x unit of time (if you want a 24 hour average, take the number of blocks in the past 24 hours). As of the time of this post, 170 blocks have been solved in those 24 hours. This implies an expected 24*3.3e16 or 8e17 hashes have been computed. Divide by 86400 (seconds in a day) and you get 9.26e12, or 9.26 TH/s. The site reports 6.5 TH/s, presumably because it uses a longer window than 24 hours (probably 7 days). Just because it's a statistical average instead of the exact rate doesn't mean it's 100% bogus. If you want, you can use fairly standard statistical models to find an acceptable error margin.
- deepblueocean 14y ago
  It doesn't bother you that your method counts only unique hash values tested? Or that this value is being used on the site to talk about power expenditure (which is clearly related to total hashes per second, not unique hashes)? You're right that you can compute the N-second average rate easily. But nobody reports the "network hash rate" as such. And since the denominator matters a lot in determining what the number means, pretty much all the numbers you find out in the world are (1) misreported and (2) bogus.
  - gibybo 14y ago
    It does count only unique hash values, but why should that bother me? People don't randomly generate the same 256 bit number very often (in fact, the probability is so low that it has almost certainly never happened) When I search for "bitcoin network hashrate" on google, the first link is http://bitcoin.sipa.be/ http://bitcoin.sipa.be/, which does in fact report the N-second average rate. It reports the 7-days, 14-day, and 30-day average rate.

maxerickson 14y ago

The network collaborates to adjust the mining difficulty, to keep the rate of new coins approximately the same over time: https://en.bitcoin.it/wiki/Difficulty https://en.bitcoin.it/wiki/Difficulty There is a linear relationship between the hash rate and the difficulty (there is further discussion at that link).

deepblueocean 14y ago
I'm aware of that. rwinn, can you tell me if this is what you're doing? It's in your last sentence that you go wrong. There's a relationship between the number of expected hashes per new block and the difficulty. That tells you something about the hash rate, but not the rate itself. Actually, it tells you something about the number of unique hashes being tried per new block (in expectation). And for some applications, that may, in fact, be what you care about. Specifically, the appearance of new blocks is, if you like, a random variable with an exponential distribution. You can, in principle, estimate the rate parameter for this distribution using the difficulty and the timestamps in the Bitcoin log, but it's not straightforward. The last time I got into it, I was halfway through building a Bayesian estimator for the rate parameter using the log before I had to give up and move on to real work. I'll do it soon.
- maxerickson 14y ago
  I don't see how a hash (as a token of bitcoin work) would be anything other than unique (for the result to be useful to me it has to include my address in the input). In what applications would the likely immediate hash rate be more useful than the historical average hash rate? I guess the obvious one is turning some bit of mining hardware on and off.

gibybo 14y ago

100% bogus? I'm not sure what bad/incorrect statistics you are referring to since it's relatively straight forward to find. The current target hash is "0x000000000000022FBE0000000000000000000000000000000000000000000000" This means that to solve a block, you must find a SHA-256 hash of that block's transactions + nonce that hash to a value equal or below that target. Since the output of a SHA-256 hash is essentially random, the probability of finding a nonce that evaluates to hash at or below that target is roughly [target]/[possible sha256 outputs] or 3.51e60/2^256, or 3.034e-17. On average, that means it takes 1/3e-17 or 3.3e16 hashes per block. To calculate average hashes per second of the network, we look at number of blocks solved in the last x unit of time (if you want a 24 hour average, take the number of blocks in the past 24 hours). As of the time of this post, 170 blocks have been solved in those 24 hours. This implies an expected 24*3.3e16 or 8e17 hashes have been computed. Divide by 86400 (seconds in a day) and you get 9.26e12, or 9.26 TH/s. The site reports 6.5 TH/s, presumably because it uses a longer window than 24 hours (probably 7 days). Just because it's a statistical average instead of the exact rate doesn't mean it's 100% bogus. If you want, you can use fairly standard statistical models to find an acceptable error margin.

deepblueocean 14y ago
It doesn't bother you that your method counts only unique hash values tested? Or that this value is being used on the site to talk about power expenditure (which is clearly related to total hashes per second, not unique hashes)? You're right that you can compute the N-second average rate easily. But nobody reports the "network hash rate" as such. And since the denominator matters a lot in determining what the number means, pretty much all the numbers you find out in the world are (1) misreported and (2) bogus.
- gibybo 14y ago
  It does count only unique hash values, but why should that bother me? People don't randomly generate the same 256 bit number very often (in fact, the probability is so low that it has almost certainly never happened) When I search for "bitcoin network hashrate" on google, the first link is http://bitcoin.sipa.be/ http://bitcoin.sipa.be/, which does in fact report the N-second average rate. It reports the 7-days, 14-day, and 30-day average rate.