| | 1 | = Work distribution = |
| | 2 | |
| | 3 | A host asks a project for work by including a |
| | 4 | {{{ |
| | 5 | <work_req_seconds>X</work_req_seconds> |
| | 6 | }}} |
| | 7 | element in a scheduler RPC request message. This asks the scheduler to return enough work to keep all the host's processors busy for X seconds, given the host's typical usage (i.e. the fraction of time it's turned off or BOINC is suspended, and the other processes that it executes). |
| | 8 | |
| | 9 | BOINC's work distribution policy addresses the (sometimes conflicting) goals of keeping hosts as busy as possible, while minimizing the impact of |
| | 10 | |
| | 11 | * Hosts that repeatedly return results with error outcomes, due to a host-specific problem. |
| | 12 | * Malicious participants who attempt to obtain multiple results of the same workunit, in an attempt to obtain unearned credit or have erroneous results accepted as correct. |
| | 13 | |
| | 14 | Work distribution is constrained by a number of rules: |
| | 15 | |
| | 16 | * A result is sent only if an application version is available for the host's platform. If the application's min_version field is nonzero, the version number must at list this value. |
| | 17 | * A result is not sent if its disk or memory requirements are not met by the host. |
| | 18 | * A result is not sent if the estimated latency (based on the host's CPU speed and usage parameters) exceeds the workunit's latency bound. |
| | 19 | * A result is not sent if the project has specified a [ProjectOptions#Schedulingoptionsandparameters one result per user per workunit] flag, and a result of the same workunit has already been sent to a host belonging to the same user. |
| | 20 | * A result is not sent if the project has specified a [ProjectOptions#Schedulingoptionsandparameters daily result quota per host], and the host has already been sent that many results. |
| | 21 | * A project can specify a limit on the [ProjectOptions#Schedulingoptionsandparameters number of results sent per RPC]. |
| | 22 | * A result is not sent if [HomogeneousRedundancy homogeneous redundancy] is enabled and another result of the same workunit has been sent to a different type of host. |
| | 23 | |
| | 24 | In general, the BOINC scheduler responds to a work request by enumerating unsent results from the database, filtering them by the above criteria, sending them to the host, and continuing until requested duration X is reached. |
| | 25 | |
| | 26 | For projects that have very large input files, each of which is used by many workunits, BOINC offers an alternative work distribution policy called [LocalityScheduling locality scheduling]. |
