Sum of Rec.Av.Credits weird


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Message 239 - Posted 22 Jul 2005 16:41:31 UTC

    Just curious why, or maybe a problem?

    I remember credits has been restored as good as possible but some sums of host/user/team credits may not fit (not a problem).

    But as far as I know the recent one haven't been restored respectively they will be recalculated all the time so it will not hold for more then a week, right?

    If so, I can't understand following:

    I have 3 hosts

    #70 with 33.24
    #354 with 39.22
    #356 with 50.48

    so the summary of them will be 122,94

    but profile shows 77.94

    So where are the 45 left?

    Ageless
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    Message 240 - Posted 22 Jul 2005 17:06:09 UTC

      read the <a href="http://boinc-doc.net/boinc-wiki/index.php?title=Recent_Average_Credit">Wiki</a> on that. You'll see at the bottom of the page I linked you to:

      <b>Note:</b> You cannot sum Recent Average Credit values, such as adding all of your individual computer's RAC numbers and get a meaningful answer.
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      John McLeod VII
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      Message 241 - Posted 22 Jul 2005 17:15:10 UTC

        RAC is calculated for each entity (host, user, team) separately, and the time of the calculation is important, as well as the time of the last calculation the previous value, and the credit being added to that entity. So the only time that RAC can be added is if all of the entities involved were calculated at the exact same moment. RAC is sort of a speedometer that is only updated occasionally to indicate how fast you did the trip so far.
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        Message 242 - Posted 22 Jul 2005 17:33:43 UTC

          ouch - again you pointing me to wiki ;)

          Ok - so far I understand most of it,
          although it doesn't seem very logical to me.


          What I don't get at all is this part:

          So having an old computer that is no longer producing credits does not reduce the RAC, but rather will increase it from what it would have been without the old computer. This increment will shrink until it is indistinguishable from 0.

          Having an old pc not crunching will increase RAC?

          Ageless
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          Message 243 - Posted 22 Jul 2005 17:53:42 UTC

            Well yes. When you stop crunching with one computer (or host ID), the RAC on that one will stay at whatever it was at the time you stopped. If you never add to that host ID again, the same RAC will always be added.

            It's not supposed to do that, it should deteriorate, but for some reason (unknown to me) it doesn't.

            An example to that can be seen <a href="http://setiathome.berkeley.edu/show_host_detail.php?hostid=119988">here</a>. That's my girlfriend's computer which hasn't crunched in something like 9 months. It still has a RAC, but as long as she doesn't add to it, that RAC will stay the same amount.

            As soon as she would add to the host-ID again, the RAC would drop immediately, following the rules of deterioration again.

            I hope that answers it a bit. :)
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            John McLeod VII
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            Message 244 - Posted 23 Jul 2005 4:06:17 UTC

              Assume that you have 2 machines each with a RAC of 1024 and your RAC is 2048 (because everything gets calculated at the same time - rare occurrence). At this point one of the two machines dies and you cannot afford to replace it. Its contribution to the user total RAC slowly diminishes over time. Assume that the remaining machine does steady work and maintains a RAC of exactly 1024. After a week, the residual from the no longer crunching host is 512, and the total RAC for the user is 1536. After the 10th week, the residual is 1, and the RAC for the user is 1025. After the 11th week the residual is 0.5 and the RAC for the user is 1024.5. Eventually, the residual from the old machine becomes indistinguishable from 0.

              Of course, the RAC calculations are never quite this neat as even a steady work flow just generates credit requests that have to be validated by others, and there are problems with the servers that block up granted credits. So after a few weeks the residual gets completely lost in the noise.
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              Message 245 - Posted 23 Jul 2005 8:41:19 UTC

                Of course, the RAC calculations are never quite this neat
                ==========

                My Computers are a perfect example of that John. I started this project with all my computers being attached within an 1/2 hour of each other.

                The Computer I have that has the Second highest Total Credit among my Computers has the lowest RAC yet the Computer that has the highest Total Credit has the highest RAC.

                RAC to me on the Computers means nothing because it's not a true measurement of the Computers performance.

                ric
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                Message 260 - Posted 24 Jul 2005 2:26:24 UTC

                  PoorBoy is right with his opinion, RAC means nothing, it's just a momentary
                  element.

                  Just finished a test, wanted to keep the network connections stopped until until 500 WUs have been done.

                  Unfortunately 2 PCs have been running out so I had to re-enable the network connections.

                  Right now the RAC was taking a jump, due about 470 finished WUs reported back.

                  I guess the only thing what can be taken from the RAC is, when you crunch "much" and the RAC is not moving.
                  Then this could mean, the calculation itself is "not ok".

                  This happened to me at LHC, one host was getting only 1/3 of RAC which an other host of the same speed class made.

                  Reducing the OC speed on this low RAC based host was also reducing/eleminating the "cpu error" and finaly the results could be done "ok".
                  Finaly the RAC of this corrected host was climbing.

                  As mentioned, it was at LHC, I don't know the behaviour of this project in term of "quality" of work.

                  happy crunching



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