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PPD explained

post #1 of 6
Thread Starter 
I have seen many times, questions of how the ##ll did they arrive at the number 384ppd for that WU, or 511 or 480.
I finally found the spot on the FaH site that has this explanation:

Quote:
Originally Posted by Second generation GPU client on NVIDIA hardware (GPU2) FAQ


How do you decide the credit value of GPU work units?


Points are determined by the performance of a given machine relative to a benchmark machine, similar to the CPU client benchmark process. Before releasing any new project (series of work units), we benchmark it on a dedicated computer with an ATI Radeon 3850 GPU (512 MB, 320 Stream Processors), running in a Dell Inspiron 531, with a 2.16 GHz dual core AMD 64 X2 4000+.
We plug the results of this benchmark test into the following formula:
Points = 1500 * (DaysPerWU)
where DaysPerWU is the number of days it took the benchmark hardware to complete the work unit. Note that the GPU client still relies on a fast CPU, so the CPU is an important part of this. The Points Per Day (PPD) given here assumes that a CPU is heavily needed, with a larger PPD to compensate for the use of that CPU.
Please note the very concept of a reference machine will mean that some WU performance will vary from the performance on your machine. Even between various GPU models, there are significant differences in architectures and memory speeds. Moreover, there are variations between WUs within a given project which can lead to speed differences.
Our goal is consistency within a given definition of a reference machine setup (described above), but beyond that, the natural variation from machine to machine and WU to WU will never allow any point system to perfectly predict what you get on your machine.
Source --> http://www.stanford.edu/group/pandeg...ish.FAQ-NVIDIA
post #2 of 6
Finally we have a post to link to people who go nuts about this lol
    
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post #3 of 6
Thread Starter 
Lol, maybe we can get the mods to make it a sticky.
post #4 of 6
So at least we're all getting more PPD than the reference machine!
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post #5 of 6
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When you consider that Stanford has set the expected PPD at 1500, some of us regularly get four times as many points as they expect, per client.
post #6 of 6
Quote:
Originally Posted by =Digger= View Post
When you consider that Stanford has set the expected PPD at 1500, some of us regularly get four times as many points as they expect, per client.
I fear what would happen to PPD if their antique reference machine ever gave up the ghost.
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