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diff --git a/tensorflow/docs_src/performance/xla/operation_semantics.md b/tensorflow/docs_src/performance/xla/operation_semantics.md index ccced8792e..3ca3b51a5e 100644 --- a/tensorflow/docs_src/performance/xla/operation_semantics.md +++ b/tensorflow/docs_src/performance/xla/operation_semantics.md @@ -901,95 +901,6 @@ are all 0. Figure below shows examples of different `edge_padding` and <img style="width:100%" src="https://www.tensorflow.org/images/ops_pad.png"> </div> -## Recv - -See also -[`ComputationBuilder::Recv`](https://www.tensorflow.org/code/tensorflow/compiler/xla/client/computation_builder.h). - -<b> `Recv(shape, channel_handle)` </b> - -| Arguments | Type | Semantics | -| ---------------- | --------------- | ------------------------------------ | -| `shape` | `Shape` | shape of the data to receive | -| `channel_handle` | `ChannelHandle` | unique identifier for each send/recv pair | - -Receives data of the given shape from a `Send` instruction in another -computation that shares the same channel handle. Returns a -ComputationDataHandle for the received data. - -The client API of `Recv` operation represents synchronous communication. -However, the instruction is internally decomposed into 2 HLO instructions -(`Recv` and `RecvDone`) to enable asynchronous data transfers. See also -[`HloInstruction::CreateRecv` and `HloInstruction::CreateRecvDone`](https://www.tensorflow.org/code/tensorflow/compiler/xla/service/hlo_instruction.h). - -<b>`Recv(const Shape& shape, int64 channel_id)`</b> - -Allocates resources required to receive data from a `Send` instruction with the -same channel_id. Returns a context for the allocated resources, which is used -by a following `RecvDone` instruction to wait for the completion of the data -transfer. The context is a tuple of {receive buffer (shape), request identifier -(U32)} and it can only be used by a `RecvDone` instruction. - -<b> `RecvDone(HloInstruction context)` </b> - -Given a context created by a `Recv` instruction, waits for the data transfer to -complete and returns the received data. - -## Send - -See also -[`ComputationBuilder::Send`](https://www.tensorflow.org/code/tensorflow/compiler/xla/client/computation_builder.h). - -<b> `Send(operand, channel_handle)` </b> - -| Arguments | Type | Semantics | -| ---------------- | ----------------------- | -------------------------------- | -| `operand` | `ComputationDataHandle` | data to send (array of type T) | -| `channel_handle` | `ChannelHandle` | unique identifier for each send/recv pair | - -Sends the given operand data to a `Recv` instruction in another computation -that shares the same channel handle. Does not return any data. - -Similar to the `Recv` operation, the client API of `Send` operation represents -synchronous communication, and is internally decomposed into 2 HLO instructions -(`Send` and `SendDone`) to enable asynchronous data transfers. See also -[`HloInstruction::CreateSend` and `HloInstruction::CreateSendDone`](https://www.tensorflow.org/code/tensorflow/compiler/xla/service/hlo_instruction.h). - -<b>`Send(HloInstruction operand, int64 channel_id)`</b> - -Initiates an asynchronous transfer of the operand to the resources allocated by -the `Recv` instruction with the same channel id. Returns a context, which is -used by a following `SendDone` instruction to wait for the completion of the -data transfer. The context is a tuple of {operand (shape), request identifier -(U32)} and it can only be used by a `SendDone` instruction. - -<b> `SendDone(HloInstruction context)` </b> - -Given a context created by a `Send` instruction, waits for the data transfer to -complete. The instruction does not return any data. - -<b> Scheduling of channel instructions </b> - -The execution order of the 4 instructions for each channel (`Recv`, `RecvDone`, -`Send`, `SendDone`) is as below. - -<div style="width:95%; margin:auto; margin-bottom:10px; margin-top:20px;"> - <img style="width:70%" src="../../images/send_recv_order.png"> -</div> - -* `Recv` happens before `Send` -* `Send` happens before `RecvDone` -* `Recv` happens before `RecvDone` -* `Send` happens before `SendDone` - -When the backend compilers generate a linear schedule for each computation that -communicates via channel instructions, there must not be cycles across the -computations. For example, below schedules lead to deadlocks. - -<div style="width:95%; margin:auto; margin-bottom:10px; margin-top:20px;"> - <img style="width:100%" src="../../images/send_recv_schedule.png"> -</div> - ## Reduce See also |