Milestones, cobblestones and millstones

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jacklass1
jacklass1
Joined: 18 Jan 05
Posts: 77
Credit: 7421006
RAC: 0
22 Dec 2006 1:37:08 UTC
Topic 192222
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    I've been dedicating all of my cycles on both my old (AMD AthlonXP 3000+ running XP home) and my new (AMD64bit AthlonX2 3800+ running XP Pro Media Center) to E@H. My credits have been climbing nicely and so was my RAC for a while. In the past few days, however, I find that my RAC is slowly declining. I'm sure there's a perfectly rational explanation, but I'm damned if I know what it is. Can anyone reveal the arcane secrets of credit assignment to this puzzled cruncher?

    THE MOTHER OF FOOLS IS ALWAYS PREGNANT

    Gary Roberts
    Gary Roberts
    Moderator
    Joined: 9 Feb 05
    Posts: 5872
    Credit: 117652229436
    RAC: 35178532

    Milestones, cobblestones and millstones

    22 Dec 2006 2:08:27 UTC
    Message 58205
    (moderation:
      )

      Quote:
      .... In the past few days, however, I find that my RAC is slowly declining. I'm sure there's a perfectly rational explanation, but I'm damned if I know what it is. Can anyone reveal the arcane secrets of credit assignment to this puzzled cruncher?

      Jack,

      Up until a few days ago, both your machines were crunching lots of "short" work units. There has been a changeover and now both machines are essentially crunching and returning "longs". I haven't done any hard analysis but it is my belief that short work will give you a slightly better "rate of return" credit-wise than long work. Although RAC is a bit variable at the best of times, I believe that you are simply seeing the result of this changeover.

      Another possible reason for a decline in RAC could be any increase in your level of pending credit. Your results lists show very little pending credit (because your turn around time is quite long - of the order of 5 days or more) so I don't think this is a factor.

      Exactly how much of a decline in RAC have you noticed?

      Cheers,
      Gary.

      jacklass1
      jacklass1
      Joined: 18 Jan 05
      Posts: 77
      Credit: 7421006
      RAC: 0

      RE: RE: .... In the past

      22 Dec 2006 2:15:53 UTC
      Message 58206 in response to message 58205
      (moderation:
        )

        Quote:
        Quote:
        .... In the past few days, however, I find that my RAC is slowly declining. I'm sure there's a perfectly rational explanation, but I'm damned if I know what it is. Can anyone reveal the arcane secrets of credit assignment to this puzzled cruncher?

        Jack,

        Up until a few days ago, both your machines were crunching lots of "short" work units. There has been a changeover and now both machines are essentially crunching and returning "longs". I haven't done any hard analysis but it is my belief that short work will give you a slightly better "rate of return" credit-wise than long work. Although RAC is a bit variable at the best of times, I believe that you are simply seeing the result of this changeover.

        Another possible reason for a decline in RAC could be any increase in your level of pending credit. Your results lists show very little pending credit (because your turn around time is quite long - of the order of 5 days or more) so I don't think this is a factor.

        Exactly how much of a decline in RAC have you noticed?


        THE MOTHER OF FOOLS IS ALWAYS PREGNANT

        jacklass1
        jacklass1
        Joined: 18 Jan 05
        Posts: 77
        Credit: 7421006
        RAC: 0

        RE: RE: .... In the past

        22 Dec 2006 2:20:25 UTC
        Message 58207 in response to message 58205
        (moderation:
          )

          Quote:
          Quote:
          .... In the past few days, however, I find that my RAC is slowly declining. I'm sure there's a perfectly rational explanation, but I'm damned if I know what it is. Can anyone reveal the arcane secrets of credit assignment to this puzzled cruncher?

          Jack,

          Up until a few days ago, both your machines were crunching lots of "short" work units. There has been a changeover and now both machines are essentially crunching and returning "longs". I haven't done any hard analysis but it is my belief that short work will give you a slightly better "rate of return" credit-wise than long work. Although RAC is a bit variable at the best of times, I believe that you are simply seeing the result of this changeover.

          Another possible reason for a decline in RAC could be any increase in your level of pending credit. Your results lists show very little pending credit (because your turn around time is quite long - of the order of 5 days or more) so I don't think this is a factor.

          Thanks for the quick response Gary. I just took a look at my current cache of WU's on my dual processor. The bulk of these are short ones. In contrast, most of the cache on my old machine are long ones. However, just to add a little variety in things:

          When I made the first post above my RAC had gone from about 1200 to around 1134 over the past three or four days. I just took another look, and I find that my RAC is now about 1217. I returned 17 short WUs from the new box a little while ago, so perhaps that is what brought the RAC back up. However, I find the process mysterious. However, I find many things mysterious and have learned to take an even strain and live with them.

          Thanks again for your help.
          Jack

          Exactly how much of a decline in RAC have you noticed?


          THE MOTHER OF FOOLS IS ALWAYS PREGNANT

          AnRM
          AnRM
          Joined: 9 Feb 05
          Posts: 213
          Credit: 4346941
          RAC: 0

          RE: .....Exactly how much

          22 Dec 2006 7:33:08 UTC
          Message 58208 in response to message 58205
          (moderation:
            )

            Quote:

            .....Exactly how much of a decline in RAC have you noticed?


            Hi Gary, it's great to have your expertise on the 'Boards' again.....Cheers, Rog.

            jacklass1
            jacklass1
            Joined: 18 Jan 05
            Posts: 77
            Credit: 7421006
            RAC: 0

            RE: RE: .....Exactly how

            22 Dec 2006 8:32:28 UTC
            Message 58209 in response to message 58208
            (moderation:
              )

              Quote:

              Quote:

              .....Exactly how much of a decline in RAC have you noticed?


              Hi Gary, it's great to have your expertise on the 'Boards' again.....Cheers, Rog.

              Well, it seems to be climbing again. However, it down 1217-1207 since last I posted. I don't really think there's anything amiss. I just really don't understand the relationship betweens credit received and RAC. Is there a simple ratio, or does the size of a work unit (and thus the credit) also come into it?
              That is, is the RAC proportional to the actual computer time? At any rate, it isn't something to lose sleep over. "And so to bed."

              THE MOTHER OF FOOLS IS ALWAYS PREGNANT

              Michael Karlinsky
              Michael Karlinsky
              Joined: 22 Jan 05
              Posts: 888
              Credit: 23502182
              RAC: 0

              RE: I just really don't

              22 Dec 2006 8:49:07 UTC
              Message 58210 in response to message 58209
              (moderation:
                )

                Quote:
                I just really don't understand the relationship betweens credit received and RAC. Is there a simple ratio, or does the size of a work unit (and thus the credit) also come into it?
                That is, is the RAC proportional to the actual computer time? At any rate, it isn't something to lose sleep over. "And so to bed."

                BOINC WIKI on RAC

                Michael

                Team Linux Users Everywhere

                Gary Roberts
                Gary Roberts
                Moderator
                Joined: 9 Feb 05
                Posts: 5872
                Credit: 117652229436
                RAC: 35178532

                RE: RE: .....Exactly how

                22 Dec 2006 11:56:40 UTC
                Message 58211 in response to message 58208
                (moderation:
                  )

                  Quote:
                  Quote:
                  .....Exactly how much of a decline in RAC have you noticed?

                  Hi Gary, it's great to have your expertise on the 'Boards' again.....Cheers, Rog.

                  Hi Rog,

                  Thanks for your kind words. I've been busy with other things but I do look in at what is going on from time to time. It was just pure chance that I saw Jack's post just after he made it so I made the time to answer.

                  Cheers,
                  Gary.

                  Gary Roberts
                  Gary Roberts
                  Moderator
                  Joined: 9 Feb 05
                  Posts: 5872
                  Credit: 117652229436
                  RAC: 35178532

                  RE: Well, it seems to be

                  22 Dec 2006 12:23:11 UTC
                  Message 58212 in response to message 58209
                  (moderation:
                    )

                    Quote:

                    Well, it seems to be climbing again. However, it down 1217-1207 since last I posted. I don't really think there's anything amiss.

                    No, there's absolutely nothing amiss.

                    Quote:

                    I just really don't understand the relationship betweens credit received and RAC. Is there a simple ratio, or does the size of a work unit (and thus the credit) also come into it?
                    That is, is the RAC proportional to the actual computer time? At any rate, it isn't something to lose sleep over. "And so to bed."

                    Michael's link to the Wiki is the definitive answer but if you want a simplified version consider the following. RAC is just a glorified moving average of the rate at which you are accumulating credit. In a perfect world, if you were reporting results immediately they were finished and uploaded and if your quorum partner was prompt and doing the same, you should have (when things are settled) a static value for RAC equal to your daily credit increase. However, if there is any "burstiness" in the rate at which you report results or if your results are "pending" rather than immediately validated, you will have a fluctuating RAC. In an earlier post you mentioned returning 17 results in a batch. While accumulating (but not reporting) those results, your RAC would have tended to decline. The moment those results were reported and validated, you would have seen a burst in total credit but also a more gentle upward spike in RAC because it is a moving average after all.

                    Cheers,
                    Gary.

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