New BOINCers and gridcoin miners look for basic information on RAC (Recent Average Credit) or how many GRC they can receive for their research. Let’s see how to calculate them quickly, but first – what is RAC?

Let’s think about scientists (project administrators) as a pack of wolves and us, researchers (BOINCers), as rabbit breeders, who raise them for wolves! Or if you prefer you can think of scientists as rabbits and us as carrot growers :)

Sometimes rabbits (neutered) are dispatched to the fields. Wolves would like to know how many rabbits are out there on a typical day. As rabbits die from natural causes, are delivered by breeders at random times, by some farmers just once a week, by others several times a day, wolves had to come with a **clever way**(1) to calculate average number of rabbits. Wolves keep track of the total number of rabbits released by each farmer and also this magic daily average - RAC. As a farmer, you might be interested to find out what RAC you can get from wolves, especially if you expect government donations (GRC) that are based on RAC!

**Calculate you maximum RAC in 5 seconds**

For some projects (like Amicable Numbers) it’s easy. Conditions:

- project awards the same number of credits for each Work Unit (WU)
- time to run each WU is roughly the same

Your max achievable RAC is equal to a number of WUs your computer can work through a day (24h) multiplied by credit awarded for each WU:

Max RAC = (number of WU per day) x (credit for one WU)

For example, if it takes 1 hour to process one WU, credit for each WU is 1000, maximum RAC you can achieve is: 24 x 1000 = 24000

As some projects have irregular work units, some huge and some small, it’s not so straightforward, but you can still get some estimations.

**How much time you need to achieve maximum RAC?**

Short answer – you should never get to a theoretical maximum. But you can get very close to or even surpass it for a short time (in some circumstances, see below).

Often you will get to:

- 50 % of your max RAC after 7 days
- 75 % of your max RAC after 14 days
- 88 % of your max RAC after 21 days
- 94 % of your max RAC after 28 days
- 97 % of your max RAC after 35 days

**A trick to reach 100% of maximum RAC in 7 days.**

In some circumstances you can achieve 100% of your theoretical maximum RAC or even surpass it (temporarily) in just a few days. Let’s assume you have just started above project on your laptop. As you do a lot of other stuff, it will work 6 hours a day on the project. Thus maximum RAC it will achieve will be 6 x 1000 = 6000. However, you are going on holidays for a whole week. Now you can leave your laptop on 24/7. After coming back from holidays your RAC = 0.5 x 24000 = 12000. Now you switch to 6 hours a day and your RAC will slowly drop to your ‘average maximum’ of ~6000.

Or, instead of RAC = 12 000, you find your laptop fried! It’s worth to check how your computer works under load, whether there are no overheating issues. So monitor temperatures, adjust BOINC parameters.

Real world example:

Assuming you do 24 work units a day in Amicable Numbers project, your RAC will grow, more or less, as follows:

**How many GRC will I get?**

Let’s assume there are 24 (whitelisted) scientific projects (as it is at the time of writing this post) and that daily average PoR bounty is 48 000 GRC (what is around the official target now). Thus there is a 2 000 GRC per project each day to claim. To calculate your daily reward for an individual project should suffice:

Reward = 2 000 x (my RAC) / (team Gridcoin RAC)

But it won’t work due to current miscalculations in the network. Currently only around 27 000 GRC are distributed via PoR. Thus following equation to calculate daily reward gives better estimates:

Reward = 1 200 x (my RAC) / (team Gridcoin RAC)

To find out current actual PoR daily reward, in linux terminal you can use

- gridcoinresearchd list network

command.

I guess it also works in windows command line.

**NOTE.** Developers are aware of these problems and are working on code improvements. Not only 48000 GRC a day (or 50000) target should be achieved, but RAC might not be used at all to calculate GRC awards.

NOTE 2. If you’ve just started, your first reward will be 1 GRC.

--- End of main article ---

*5 second calculation - works for some projects only

**(1) equation to calculate RAC**

It seems explanations of RAC that pop up at the top of google search are sloppy, like old BOINC wiki article

or this forum discussion

Seems like equations / code from these are used in some new articles.

For a decay function they use a strange construct:

decay = exp( (-t/th) x ln(2) )

where th = half-life time.

Note that:

decay = exp( (-t/th) x ln(2) ) = e^( (-t/th) x ln(2) ) = e^( ln(2^(-t/th)) ) = 2^(-t/th)

or:

decay = (1/2)^(t/th)

No exp or logarithm needed, easier to calculate and easier to understand.

Which is a part of the basic exponential decay equation you can read more on wikipedia.

N(t) = N(0) x (1/2)^(t/th)

From this equation we can find how quickly radioactive substance decays or how quickly rabbits disappear if we know a constant th (half-life) and N(0) – initial count. (Half life = 6 moths would mean that after 6 months initial number of 1000 neutered rabbits would fall to 500). If t = th we get:

N(t=th) = (½) x N(0)

As in BOINC (or farming) we ‘generate’ new credits (or rabbits), we have to modify exponential decay equation to the following form:

N(t) = N(0) x 2^(-t/th) + Nnew

Where Nnew is a (adjusted) number of newly added credits (rabbits).

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