Is it possible to get an accruate Mhash rate based on number of shares

[Xenland]

Believe me when I tell you, I know it sounds like a stupid question but seriously is it possible to get an accurate Mhash rate based on the share data pushpoold submits?
All my formulas come out accurate at first but once there its more or less workers they go off the charts in accurate!
I've seen other pooling services make this mistake of inaccuate hashing scores mine are usually at a ~20 Mhash/s error rate, which might piss some
new combing miners off when they come to find that they "Might" be making less Mhashes then their minors are reporting.

So is it possible to get an accruate mhash rate with the following data per share submitted
Fields:
id | timestamp | username

This is the last formula I attempted to use

Most recent share  submitted in time stamp
Minus(-)
First share submitted in round time stamp
Equals = Total Time Connected

TotalTimeConnected
Divided By(/)
Total Shares Subbmitted this round
Equals = Failed horribly at accurate Mhash Rate.

[redhatzero]

I'm using s.th. Like this (got some hints in the Pushpool thread):

NrOfShares / timeframe * 4294967296

That should be hashes per second if pushpool is rewriting difficulty to 1

But due to the nature of shares, I wouldn't call that accurate. It will always be more like a guess

[Xenland]

I'm using s.th. Like this (got some hints in the Pushpool thread):

NrOfShares / timeframe * 4294967296

That should be hashes per second if pushpool is rewriting difficulty to 1

But due to the nature of shares, I wouldn't call that accurate. It will always be more like a guess

Is this the current difficulty?
4294967296

[PwrLeveld]

No, I don't beleive so. However, I do not know the current dificulty but it says it in the wiki.

[redhatzero]

No, it's 2^32 which should be the whole keyspace for one workpacket if I remember right

http://forum.bitcoin.org/index.php?topic=8707.msg137869#msg137869

[M2Ys4U]

Hashes per second = Number of shares * 2^32 / time delta

Where time delta is the number of seconds you're reporting the hashrate average over.

[Xenland]

So i used this formula and i got 8 hashes per second?

Update: I figured out i did the formula backwards but its still not even close?

$hashesPerSecond =  $numShares / $fiveMinutesAgo * 4294967296;
The result is 16.345 Hahses/s
but my miner runs as 85000 Khash/s

UPDATE: I was using $fiveminutesago, and not the amount of time that has passed

[M2Ys4U]

It will vary wildly. Using that formula, a 600 second time delta and approx 66MHash/s I get reports between 20MHash/s and 120MHash/s, but that's just statistical variance.

[Xenland]

It almost seems like we should use a Minutes Per Share graph instead of an Mhash graph since they are so unpredictably inaccurate.