# Computation credit

A BOINC project gives you **credit** for the computations your computers perform for it.
BOINC's unit of credit, the **Cobblestone** (named after Jeff Cobb of SETI@home),
is 1/200 day of CPU time on a reference computer that does
1,000 MFLOPS based on the Whetstone benchmark

Eventually, credit may reflect network transfer and disk storage as well as computation.

Credit has no monetary or other value; it's just a measure of how much work your computers have done.

## Credit and FLOPS

The average FLOPS (floating point operations per second) achieved by a computer or group of computers can be estimated from its Recent Average Credit (RAC) as follows:

GigaFLOPs = RAC/200 TeraFLOPS = RAC/200,000

(Remember that a 1 GigaFLOP machine, running full time, produces 200 units of credit in 1 day).

The credit figures for a particular day may be distorted if a project is catching up or falling behind on validation (the process or granting credit). Thus to get accurate FLOPS estimates you should look at average RAC over a period of a week or so.

## Recent Average Credit

Projects maintain two counts of granted credit:

**Total credit**: The total number of Cobblestones performed and granted.**Recent average credit**: The average number of Cobblestones per day granted recently. This average decreases by a factor of two every week.

Both quantities (total and recent average) are maintained for each user, host and team.

## How benchmarks are calculated

'Whetstone' is a benchmark that is reported as 'Measured floating point speed'. Floats can have fractional parts (like 1.48283 or 3.141592); Whetstone does 8 different groups of tests (repeatedly of course), times how long they took to finish, and produces a number, [ops performed]/[time]. These tests all use floating point math operations of the CPUs being tested. Some of them are simple math (addition, multiplication, division) while others compute trigonometric and exponential functions (sine, cosine, tangent, exponent). Neither of the tests really checks how well/fast a system can access memory, and most BOINC applications access memory a lot.