Short answer: it varies! On the average computer, the average work unit takes about 10 hours. Sometimes you may get work units that take days to complete, or ones that complete quickly.

Long answer
After your World Community Grid agent is installed, it asks the server for a "work unit" to process. In the case of the Human Proteome Folding project, a work unit consists of a particular gene sequence and instructions for how many different foldings of the corresponding protein should be computed on your computer ("device"). We have no way to predict how long each folding will take because the process is based on random numbers. However, we have a reasonable guess based on the length of the gene sequence and how long it has taken to compute others of the same length. Using this information, we try to tune the work unit instructions so that an average computer would complete a work unit in about 10-20 hours of CPU time, on the average.

Several factors can greatly affect the actual Run time for a particular work unit. First, even though most foldings take just a few minutes to process, a few percent of them can take an hour or more. Since we have no way to predict if a given work unit will have more than an average share of these more difficult foldings, we find that the run time for a work unit can occasionally increase by a factor of ten. For this reason, we are considering reducing the average run time, which would correspondingly reduce the run times of the occasional very long work units.

There are other factors, which can affect the run time. First, computers run at different speeds. Thus a high-end computer might be able to get through an average work unit in just four hours, while slower computers might take a sixty or more. Second, we have changed the text on your agent from "CPU time" to "Run time." This change will appear the next time your agent communicates with the server, at which time your software firewall might also prompt you for permission to allow the new agent to access the Internet. The time indicated there is actually the time during which your agent is available to run, not the precise CPU time used. If anything else on your system needs CPU time, the agent yields to that other process. Thus, other work on your computer will make it appear that your agent is taking longer to process a work unit because it is not able to use most of the CPU time. We have sometimes seen print spoolers, virus scanners, and other such activity consume most of the CPU time, not permitting the grid agent to make much progress. If you are curious to see how much CPU time your agent is getting, you can use the Task Manager to take a look at the process called "WCGrid_Rosetta." Combining these factors with the variation in work unit times above can lead to an even wider range of run times. So please do not be frustrated if you happen to have a longer running work unit. All of the computations your computer is performing are very valuable to us. As we get more statistics about the length of time the work units take to process, we will continue to tune our prediction formula to minimize the number of really long runs.