# How do we calculate RAC -- For Dummies?

merle van osdol
Joined: 1 Mar 05
Posts: 513
Credit: 60,724,446
RAC: 0
Topic 198207

I have asked this question before with boinc groups but always get the same answer. A link to the actual formula to calculate RAC. Which doesn't help me much.
So I thought up this way of asking the same question:
If in the current moment I am granted 10,000 credits, what is it worth in RAC value:

in one second =
in 30 days =
in 60 days =
in 90 days =

Thanks

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

Logforme
Joined: 13 Aug 10
Posts: 332
Credit: 1,714,373,961
RAC: 0

### How do we calculate RAC -- For Dummies?

Recent Average Credit (per day).
It means that on average your computers produces 10,000 credits per day. Just divide and multiply to convert from days to seconds and centuries.

archae86
Joined: 6 Dec 05
Posts: 3,145
Credit: 7,053,594,931
RAC: 1,633,830

### RE: If in the current

Quote:

If in the current moment I am granted 10,000 credits, what is it worth in RAC value:

Two simple rules get you very close.

1. At the moment of award, 1 point in credit bumps up your RAC by just about 0.1.
2. The RAC contribution of already credited work decays a factor of two per week.

Applying those rules and rounding aggressively, would give estimates of answers to your question of:

in one second = 1000
in 30 days = 51
in 60 days = 3
in 90 days = 0

merle van osdol
Joined: 1 Mar 05
Posts: 513
Credit: 60,724,446
RAC: 0

### RE: RE: If in the

Quote:
Quote:

If in the current moment I am granted 10,000 credits, what is it worth in RAC value:

Two simple rules get you very close.

1. At the moment of award, 1 point in credit bumps up your RAC by just about 0.1.
2. The RAC contribution of already credited work decays a factor of two per week.

Applying those rules and rounding aggressively, would give estimates of answers to your question of:

in one second = 1000
in 30 days = 51
in 60 days = 3
in 90 days = 0

I like it. It seems to make sense from my experience. That's a fast decay. Makes me feel like a lab rat running on a wheel. :-)

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

Daniels_Parents
Joined: 9 Feb 05
Posts: 101
Credit: 1,877,689,213
RAC: 0

### RE: That's a fast decay.

Quote:
That's a fast decay. Makes me feel like a lab rat running on a wheel. :-)

So it could probably be a good idea to rename RAC to RAT = Recent Average Turns :-)))

Cheers,
Arthur

I know I am a part of a story that starts long before I can remember and continues long beyond when anyone will remember me [Danny Hillis, Long Now]

merle van osdol
Joined: 1 Mar 05
Posts: 513
Credit: 60,724,446
RAC: 0

### RE: RE: That's a fast

Quote:
Quote:
That's a fast decay. Makes me feel like a lab rat running on a wheel. :-)

So it could probably be a good idea to rename RAC to RAT = Recent Average Turns :-)))

Cheers,
Arthur

Recent Attenuated Turns?

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

mikey
Joined: 22 Jan 05
Posts: 11,936
Credit: 1,832,078,092
RAC: 213,049

### RE: RE: RE: That's a

Quote:
Quote:
Quote:
That's a fast decay. Makes me feel like a lab rat running on a wheel. :-)

So it could probably be a good idea to rename RAC to RAT = Recent Average Turns :-)))

Cheers,
Arthur

Recent Attenuated Turns?

Think of RAC as a speedometer in your car, the harder you press the gas pedal, or more machines you use to crunch with, the faster you go, but as soon as you lift your foot off the gas, or stop using some machines, the slower you will go. Some projects give a ton of rac per workunit completed, others not so much, this has been debated thoroughly over the years and this is not the place to rehash it again, just suffice it to say each project can set it the way they like it to be. This means if you are crunching for project A and it gives out twice as much rac as project B for a similar amount of work your rac will be higher even though you aren't working harder, or pressing the pedal closer to the floor. Because each project sets their own credits it is therefore best to use rac as a comparison at the SAME project, not across projects.

merle van osdol
Joined: 1 Mar 05
Posts: 513
Credit: 60,724,446
RAC: 0

### Sorry Mikey, We were just

Sorry Mikey,
We were just joking around. Helps me get over my own boredom.

Quote:
Quote:
Quote:
Quote:
That's a fast decay. Makes me feel like a lab rat running on a wheel. :-)

So it could probably be a good idea to rename RAC to RAT = Recent Average Turns :-)))

Cheers,
Arthur

Recent Attenuated Turns?

Think of RAC as a speedometer in your car, the harder you press the gas pedal, or more machines you use to crunch with, the faster you go, but as soon as you lift your foot off the gas, or stop using some machines, the slower you will go. Some projects give a ton of rac per workunit completed, others not so much, this has been debated thoroughly over the years and this is not the place to rehash it again, just suffice it to say each project can set it the way they like it to be. This means if you are crunching for project A and it gives out twice as much rac as project B for a similar amount of work your rac will be higher even though you aren't working harder, or pressing the pedal closer to the floor. Because each project sets their own credits it is therefore best to use rac as a comparison at the SAME project, not across projects.

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

Stan Pope
Joined: 22 Dec 05
Posts: 80
Credit: 426,811,575
RAC: 0

### RE: I have asked this

Quote:
I have asked this question before with boinc groups but always get the same answer. A link to the actual formula to calculate RAC.

Argh!!! I've poked about BOINC and this forum off and on for several years looking for that formula! And you get it handed to you! :)

I think I know what it is, but would like to be sure, so would somebody share it again, please?

I think that it is an exponential moving average with an alpha of approximately 0.1/day.

Simulating that with a spreadsheet suggests that the more often one updates to get newly earned credits pushed into the RAC, the more slowly the RAC grows toward equilibrium! If true, it is mighty clever of our esteemed developers to structure the scorekeeping algorithm to slightly penalize such unproductive loading of the servers! :)

Stan

mikey
Joined: 22 Jan 05
Posts: 11,936
Credit: 1,832,078,092
RAC: 213,049

### RE: RE: I have asked this

Quote:
Quote:
I have asked this question before with boinc groups but always get the same answer. A link to the actual formula to calculate RAC.

Argh!!! I've poked about BOINC and this forum off and on for several years looking for that formula! And you get it handed to you! :)

I think I know what it is, but would like to be sure, so would somebody share it again, please?

I think that it is an exponential moving average with an alpha of approximately 0.1/day.

Simulating that with a spreadsheet suggests that the more often one updates to get newly earned credits pushed into the RAC, the more slowly the RAC grows toward equilibrium! If true, it is mighty clever of our esteemed developers to structure the scorekeeping algorithm to slightly penalize such unproductive loading of the servers! :)

Here's a start:
http://boinc.berkeley.edu/wiki/Computation_credit

Richard Haselgrove
Joined: 10 Dec 05
Posts: 2,140
Credit: 2,768,562,417
RAC: 972,329

### The best description was

The best description was probably in the old Unofficial BOINC Wiki. That's been allowed to lapse, and the domain name has been taken over by a squatter, but it can still be found in the Wayback Machine archive.

http://web.archive.org/web/20120418125739/http://www.boinc-wiki.info/Recent_Average_Credit

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