More about Credits, GFlops, G-hours, and CPU hours

Statistics and charts at GridRepublic use a variety of units. This article seeks to explain those units.

Credits

Projects give you credit for the computations your computers perform.

Definitition

GridRepublic, and all projects available through GridRepublic, are built using BOINC. BOINC's unit of credit, the Cobblestone (named after Jeff Cobb of SETI@home), is 1/100 day of CPU time on a reference computer that does both

• 1,000 double-precision MIPS based on the Whetstone benchmark, and
• 1,000 VAX MIPS based on the Dhrystone benchmark.

So it follows that a more powerful machine earns more credits per hour of work than a less powerful machine, because it does more computation in that time. (ie, a machine capable of 2,000 MIPS will earn 2 credits in 1/100 day).

Of course, credit has no monetary or other value; it's just a measure of how much work your computers have contributed.

How Credit is Determined

When you first run GridRepublic Desktop (or BOINC), the software runs a series of benchmark tests to determine the speed of your machine. When your computer subsequently completes a result, the desktop software determines an amount of claimed credit in one of two ways:

• In general, the claimed credit is the result's CPU time multiplied by the CPU benchmarks. NOTE: the desktop software is not optimized for specific processors. Its benchmark numbers may be lower than those produced by other programs.
• Some applications determine claimed credit themselves. This would be the case, for example, with applications that use graphics coprocessors or other non-CPU hardware.
• further details about claimed credit

Note that the granted credit that you receive may be different from the claimed credit, and there may be a delay of a few hours or days before it is granted. This is because some projects grant credit only after results have been validated.

The validation process involves comparison of your computer's work product to other computers. When projects are falling behind or catching up on validation, there can be delays in the granting of credit. (more)

Credit Statistics

Projects maintain two counts of granted credit:

• Total credit: The total number of Cobblestones performed and granted.
• Recent average credit (RAC): The average number of Cobblestones per day granted recently.

Credits and Flops (and GFlops and TFlops)

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/100
• TeraFLOPS = RAC/100,000

(Remember that a 1 GigaFLOP machine, running full time, produces 100 units of credit in 1 day).

As noted above, 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.

Credits and G-Hours or CPU-hours

Converting Credits to G-hours or CPU-hours is straightforward (G-hours and CPU-hours are two different names for the same thing): as noted above, a Credit is 1/100 day on a reference machine. Therefore 100 credits is 24 hours of computing; 1 credit is 24/100 or 0.24 hours. (Said another way, Credits * 0.24 = G-hours or CPU-hours).

Note that the result of this computation likely will not correspond to actual clock time on your machine, as your machine will almost certainly be faster or slower than the reference machine.