Wall clock vs CPU clock

Message boards : Number crunching : Wall clock vs CPU clock

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Profile sslickerson

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Message 61606 - Posted: 7 Jun 2009, 15:52:51 UTC

I've recently noticed that BOINC manager displays elapsed time as the time it took for the workunit to finish including time in which the CPU was being used for some other task.

For instance, this workunit shows a CPU time of about 86400 seconds (my runtime is 24 hours) but BOINC manager showed over 29 hours to complete or about 105,000 seconds.

THE RDCF for this laptop is 4.8. I manually changed the RDCF to 1 and uploaded two wu which in turn changed it back to 4.8.

This computer claimed 381 credits for that workunit and was granted 147! This is typical for all workunits on this computer.

Is there something going on here or can I expect this continue because it really stings when I can expect granted credit to be only 40% of claimed credit.

Timothy



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Profile Hammeh

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Message 61608 - Posted: 7 Jun 2009, 18:19:50 UTC

Credit given in this project is based on the actual amount of work done and not the amount of CPU Time. Credit for Rosetta is given according to the number of decoys generated in the task. More information on the credit system can be found here.
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Profile sslickerson

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Message 61611 - Posted: 7 Jun 2009, 23:00:19 UTC - in response to Message 61608.  
Last modified: 7 Jun 2009, 23:05:47 UTC

Credit given in this project is based on the actual amount of work done and not the amount of CPU Time. Credit for Rosetta is given according to the number of decoys generated in the task. More information on the credit system can be found here.


Ok I understand that but it brings up another question then.

Typically my laptop is far slower than my desktop as shown here: laptop, desktop.

Both of these two above workunits completed 99 decoys and were thus stopped by the watchdog. My desktop did it about 3 times faster than the laptop but was granted about 1.5 times the credit. I understand that different wu's get different granted credit but it seems to me that if all things are considered equal when time is not a factor (i.e. OS and BOINC version do not matter) then shouldn't these both get the same credit even though they are of different types? They both did 99 decoys, that is to say they both did the same amount of work but it seems that my slow laptop is getting more credit than it deserves but my faster desktop is getting less.

Sure there might be parity among all computers doing the same type of wu but it seems there is not parity among all types of workunit which then leads to inflated/deflated credit based on someone simply placing a number of indeterminate value on a wu (because each wu is valued in comparison to itself not all the other dozens of wu.)

I don't know, perhaps it all evens out in the end, but if appears there is too much guesswork going on here.

Thanks,

Timothy

Edit: from the time I wrote this and posted it my link for the laptop went dead. The one that is currently there is close to the original one I was referencing but not quite but I still think it holds.
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Profile Paul D. Buck

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Message 61615 - Posted: 8 Jun 2009, 6:49:05 UTC

My experience is that the RaH system does not award based on the number of decoys in that I have had many tasks returned with higher decoy counts that earn less than other tasks with lower decoy counts.
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Profile Hammeh

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Message 61619 - Posted: 8 Jun 2009, 9:04:30 UTC

From the Credit System Explained Article:
For each work unit type, we keep track of the total amount of claimed credits and structures from valid results returned by hosts, and we use these running totals to determine the amount of credit to award per structure.

Clealy if your laptop got more credits for the same number of decoys then each structure created for the workunit it was processing was awarded more credit than the one your desktop was running.
All credit comparisions between your two computers will even out and the fast computer will eventually have a higher RAC provided they are both crunching under the same conditions/preferences. If your desktop completes tasks faster than your laptop then it will start a new scan and therefore start earning more credits from it.
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Message boards : Number crunching : Wall clock vs CPU clock



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