Task Interface

A task which may be repeated in parallel with different inputs.

Task should represent an instance of the task to complete (e.g. a Metropolis-Hastings random walk). It should provide the following methods.

typedef .. ResultType

An alias for the type of, e.g. a structure, which contains the result of the given task. See Task::getResult().

typedef .. StatusReportType

The type storing information for a status report (task progress, message, additional info such as acceptance ratio etc.). This class must inherit from Tomographer::MultiProc::TaskStatusReport, such that at least fraction_done and msg are provided. (So that generic status reporter helpers such as Tomographer::Tools::SigHandlerTaskDispatcherStatusReporter can at least rely on this information.)

Task(InputType input, const TaskCData * pcdata, LoggerType & logger)

Task constructor: construct a Task instance which will solve the task for the given input. The input parameter is whatever TaskCData::getTaskInput() returned.

This method can log to the given logger (see Tomographer::Logger::LoggerBase). Note that the logger need NOT be the logger that may have been specified, e.g., to the task dispatcher: it could be, for example, an internal thread-safe wrapper to your original logger. To be sure, you should make this a template method with a parameter LoggerType.

void run(const TaskCData * pcdata, LoggerType & logger, TaskManagerIface * tmgriface)

This method actually runs the task.

This method can log to the given logger (see Tomographer::Logger::LoggerBase). Note that the logger need NOT be the logger that may have been specified, e.g., to the task dispatcher: it could be, for example, an internal thread-safe wrapper to your original logger. To be sure, you should make this a template method with parameters LoggerType and TaskManagerIface.

The code in run() should poll tmgriface->statusReportRequested() and provide a status report if requested to do so via tmgriface->statusReport(const TaskStatusReportType &). tmgriface is an object which complies to the TaskManagerIface Interface.

ResultType getResult()

Return a custom type which holds the result for the given task. This will be given to the result collector (see ResultsCollector Interface).

Note on Status Reports:

Tasks must regularly check whether a status report has been requested as they run. This is done by regularly calling the function tmgriface->statusReportRequested() on the tmgriface object provided to TaskType::run(). This function call is meant to be very efficient (for example, it does not require a critical section in the OpenMP implementation), so this check can be done often. The function tmgriface->statusReportRequested() returns a bool indicating whether such a report was requested or not. If such a report was requested, then the thread should prepare its status report object (of type TaskStatusReportType), and call tmgriface->submitStatusReport(const TaskStatusReportType & obj).

The task should provide a member type named StatusReportType, which can be for example a simple typedef to Tomographer::MultiProc::TaskStatusReport, which specifies the type of its status reports.