fi_trigger(3) Libfabric Programmer's Manual
fi_trigger - Triggered operations
Triggered operations allow an application to queue a data transfer request that is deferred until a specified condition is met. A typical use is to send a message only after receiving all input data.
A triggered operation may be requested by specifying the FI_TRIGGER flag as part of the operation. Alternatively, an endpoint alias may be created and configured with the FI_TRIGGER flag. Such an endpoint is referred to as a trigger-able endpoint. All data transfer operations on a trigger-able endpoint are deferred.
Any data transfer operation is potentially trigger-able, subject to provider constraints. Trigger-able endpoints are initialized such that only those interfaces supported by the provider which are trigger-able are available.
Triggered operations require that applications use struct fi_triggered_context as their per operation context parameter. The use of struct fi_triggered_context replaces struct fi_context, if required by the provider. Although struct fi_triggered_context is not opaque to the application, the contents of the structure may be modified by the provider. This structure has similar requirements as struct fi_context. It must be allocated by the application and remain valid until the corresponding operation completes or is successfully canceled.
Struct fi_triggered_context is used to specify the condition that must be met before the triggered data transfer is initiated. If the condition is met when the request is made, then the data transfer may be initiated immediately. The format of struct fi_triggered_context is described below.
The triggered context indicates the type of event assigned to the trigger, along with a union of trigger details that is based on the event type.
The following trigger events are defined.
- This indicates that the data transfer operation will be deferred until an event counter crosses an application specified threshold value. The threshold is specified using struct fi_trigger_threshold:
Threshold operations are triggered in the order of the threshold values. This is true even if the counter increments by a value greater than 1. If two triggered operations have the same threshold, they will be triggered in the order in which they were submitted to the endpoint.