# Sum of host rac does not equal total rac

[BAT] tutta55
Joined: 15 Feb 05
Posts: 17
Credit: 115,026
RAC: 0
Topic 187935

If I look at my 2 hosts running einstein, I see that the sum of the credits equals my total credit . But if I add up the recent average credit of the 2, it does not equal the overall rac at all. The sum is much higher than the overall rac. I'm sure there is a logical explanation for this, I just don't see it. Anyone?

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[B^S] Zain Upton
Joined: 11 Feb 05
Posts: 19
Credit: 15,776
RAC: 0

### Sum of host rac does not equal total rac

> If I look at my 2 hosts running einstein, I see that the sum of the credits
> equals my total credit . But if I add up the
> recent average credit of the 2, it does not equal the overall rac at all. The
> sum is much higher than the overall rac. I'm sure there is a logical
> explanation for this, I just don't see it. Anyone?
>
>

Ahhh yes the old sum of the parts not equalling the whole.

RAC is (by definition) associated with a TIMESTAMP. The RAC for your HOSTs are only updated WHEN THAT HOST returns work. The RAC for your account is calculated when THE MOST RECENT HOST has returned work.

The effect of time is to decrease RAC. So if you only have 2 computers ONE of the HOSTS RAC will be right (as part of the total), but the OTHER computer will by that stage be contributing a smaller portion than the listed RAC.

Well thats that... did what I say make any sense?

---
Zain

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[BAT] tutta55
Joined: 15 Feb 05
Posts: 17
Credit: 115,026
RAC: 0

### Thanks, Zain, I get the

Thanks, Zain, I get the picture. This also explains why in another project the rac of a now inactive host remains constant instead of decreasing over time.

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[B^S] Zain Upton
Joined: 11 Feb 05
Posts: 19
Credit: 15,776
RAC: 0

### > Thanks, Zain, I get the

Message 4942 in response to message 4941

> Thanks, Zain, I get the picture. This also explains why in another project the
> rac of a now inactive host remains constant instead of decreasing over time.
>

Your very right... it SHOULD decrease in time... but doesnt cause they never update the file until they return another bit of work.

That said... ALL the stats sites (external ones like mine, willy's, Toby's, Neil's etc) decrease the RAC properly when displaying the stats... so the RACs may be more accurate if you look on those sites (eg LHC until recently had almost a ZERO RAC across the board for every member because the project was down for nearly a month. On the LHC site RACs were high, on the external stats sites they were all depreciated properly each day).

Zain
---

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John McLeod VII
Moderator
Joined: 10 Nov 04
Posts: 547
Credit: 632,255
RAC: 0

### > > If I look at my 2 hosts

Message 4943 in response to message 4940

> > If I look at my 2 hosts running einstein, I see that the sum of the
> credits
> > equals my total credit . But if I add up the
> > recent average credit of the 2, it does not equal the overall rac at all.
> The
> > sum is much higher than the overall rac. I'm sure there is a logical
> > explanation for this, I just don't see it. Anyone?
> >
> >
>
> Ahhh yes the old sum of the parts not equalling the whole.
>
> RAC is (by definition) associated with a TIMESTAMP. The RAC for your HOSTs
> are only updated WHEN THAT HOST returns work. The RAC for your account is
> calculated when THE MOST RECENT HOST has returned work.
>
> The effect of time is to decrease RAC. So if you only have 2 computers ONE of
> the HOSTS RAC will be right (as part of the total), but the OTHER computer
> will by that stage be contributing a smaller portion than the listed RAC.
>
> Well thats that... did what I say make any sense?
>
> ---
> Zain
>
Minor correction. The RAC is updated when credit is granted after verification, not when work is returned. This is true of all projects except CPDN.

[B^S] Zain Upton
Joined: 11 Feb 05
Posts: 19
Credit: 15,776
RAC: 0

### Ahhh JM7... your always

Ahhh JM7... your always correcting me *hehehe*

Luckily your on OUR team as well... otherwise I may get a complex.

*wink*

Zain
---

Teamless? Drop by BOINC Synergy and look around
Also checkout our famous BOINC World Stats

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