/
Backend.hpp
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/
Backend.hpp
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#pragma once
#include <memory>
#include <utility>
#include <vector>
#include <ATen/ATen.h>
#include <c10/macros/Macros.h>
#include <torch/csrc/distributed/c10d/Types.hpp>
#include <torch/csrc/distributed/c10d/Utils.hpp>
#include <torch/csrc/distributed/c10d/Work.hpp>
#include <torch/csrc/distributed/c10d/debug.h>
constexpr auto kBackendDefaultTimeout =
std::chrono::milliseconds(30 * 60 * 1000);
namespace c10d {
class TORCH_API Backend : public torch::CustomClassHolder {
public:
// Backend Options is a base struct that defines the basic options
// when constructing a Backend. Each Backend subclass should
// extend this struct and define its options if it wants to provide more
// config options (beyond basic ones defined here) to end user.
struct TORCH_API Options : torch::CustomClassHolder {
explicit Options(
std::string backend,
std::chrono::milliseconds timeout = kBackendDefaultTimeout)
: timeout(timeout), backend(std::move(backend)) {}
~Options() override = default;
std::chrono::milliseconds timeout;
// backend name
const std::string backend;
};
explicit Backend(int rank, int size);
~Backend() override = 0;
int getRank() const {
return rank_;
}
int getSize() const {
return size_;
}
// Returns an unique opaque ID of this backend that can be used to correlate
// with its collectives.
int64_t getID() const {
return reinterpret_cast<std::intptr_t>(this);
}
virtual bool supportsSplitting() const {
return false;
}
virtual void startCoalescing() {
TORCH_CHECK(
false,
c10::str(
"Backend ",
getBackendName(),
" does not implement startCoalescing"));
}
virtual c10::intrusive_ptr<Work> endCoalescing() {
TORCH_CHECK(
false,
c10::str(
"Backend ", getBackendName(), " does not implement endCoalescing"));
}
// Subclasses must override this method to return the backend name
virtual const std::string getBackendName() const {
TORCH_INTERNAL_ASSERT(false, "getBackendName is not implemented.");
};
virtual c10::intrusive_ptr<Work> broadcast(
std::vector<at::Tensor>& /* tensors */,
const BroadcastOptions& /* opts */ = BroadcastOptions()) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support broadcast"));
}
virtual c10::intrusive_ptr<Work> allreduce(
std::vector<at::Tensor>& /* tensors */,
const AllreduceOptions& /* opts */ = AllreduceOptions()) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support allreduce"));
}
virtual c10::intrusive_ptr<Work> allreduce_sparse(
std::vector<at::Tensor>& /* tensors */,
const AllreduceOptions& /* opts */ = AllreduceOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ",
getBackendName(),
" does not support allreduce sparse"));
}
virtual c10::intrusive_ptr<Work> allreduce_coalesced(
std::vector<at::Tensor>& /* tensors */,
const AllreduceCoalescedOptions& /* opts */ =
AllreduceCoalescedOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ",
getBackendName(),
" does not support allreduce_coalesced"));
}
virtual c10::intrusive_ptr<Work> reduce(
std::vector<at::Tensor>& /* tensors */,
const ReduceOptions& /* opts */ = ReduceOptions()) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support reduce"));
}
virtual c10::intrusive_ptr<Work> allgather(
std::vector<std::vector<at::Tensor>>& /* outputTensors */,
std::vector<at::Tensor>& /* inputTensors */,
const AllgatherOptions& /* opts */ = AllgatherOptions()) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support allgather"));
}
// Gathers a single tensor inputBuffer into a single buffer outputBuffer that
// is interpreted as a contiguous collection of size inputBuffer * WORLD_SIZE.
// For implementers of ProcessGroup API and advanced users only.
// Note: this function will be deprecated in near future.
virtual c10::intrusive_ptr<Work> _allgather_base(
at::Tensor& /* outputBuffer */,
at::Tensor& /* inputBuffer */,
const AllgatherOptions& /* opts */ = AllgatherOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ", getBackendName(), " does not support _allgather_base"));
}
// This function is deprecated and will be moved out of Backend to comms:
// * do not add dependencies on this function,
// * do not implement it in your Backend, implement _allgather_base
// instead.
virtual c10::intrusive_ptr<Work> allgather_coalesced(
std::vector<std::vector<at::Tensor>>& /* outputTensorLists */,
std::vector<at::Tensor>& /* inputTensors */,
const AllgatherOptions& /* opts */ = AllgatherOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ",
getBackendName(),
" does not support allgather_coalesced"));
}
// This function is a coalesced version of `allgather_into_tensor` (currently
// still named as `_allgather_base`). Each tensor in the vector corresponds to
// an input/output of one `allgather_into_tensor` operation.
virtual c10::intrusive_ptr<Work> allgather_into_tensor_coalesced(
std::vector<at::Tensor>& /* outputs */,
std::vector<at::Tensor>& /* inputs */,
const AllgatherOptions& /* opts */ = AllgatherOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ",
getBackendName(),
" does not support allgather_into_tensor_coalesced"));
}
virtual c10::intrusive_ptr<Work> gather(
std::vector<std::vector<at::Tensor>>& /* outputTensors */,
std::vector<at::Tensor>& /* inputTensors */,
const GatherOptions& /* opts */ = GatherOptions()) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support gather"));
}
virtual c10::intrusive_ptr<Work> scatter(
std::vector<at::Tensor>& /* outputTensors */,
std::vector<std::vector<at::Tensor>>& /* inputTensors */,
const ScatterOptions& /* opts */ = ScatterOptions()) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support scatter"));
}
virtual c10::intrusive_ptr<Work> reduce_scatter(
std::vector<at::Tensor>& /* outputTensors */,
std::vector<std::vector<at::Tensor>>& /* inputTensors */,
const ReduceScatterOptions& /* opts */ = ReduceScatterOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ", getBackendName(), " does not support reduce_scatter"));
}
virtual c10::intrusive_ptr<Work> _reduce_scatter_base(
at::Tensor& /* outputBuffer */,
at::Tensor& /* inputBuffer */,
const ReduceScatterOptions& /* opts */ = ReduceScatterOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ",
getBackendName(),
" does not support _reduce_scatter_base"));
}
// This function is a coalesced version of `reduce_scatter_tensor` (currently
// still named as `_reduce_scatter_base`). Each tensor in the vector
// corresponds to an input/output of one `reduce_scatter_tensor` operation.
virtual c10::intrusive_ptr<Work> reduce_scatter_tensor_coalesced(
std::vector<at::Tensor>& /* outputs */,
std::vector<at::Tensor>& /* inputs */,
const ReduceScatterOptions& /* opts */ = ReduceScatterOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ",
getBackendName(),
" does not support reduce_scatter_tensor_coalesced"));
}
virtual c10::intrusive_ptr<Work> alltoall_base(
at::Tensor& /* outputBuffer */,
at::Tensor& /* inputBuffer */,
std::vector<int64_t>& /* outputSplitSizes */,
std::vector<int64_t>& /* inputSplitSizes */,
const AllToAllOptions& /* opts */ = AllToAllOptions()) {
TORCH_CHECK(
false,
c10::str(
"Backend ", getBackendName(), " does not support alltoall_base"));
}
virtual c10::intrusive_ptr<Work> alltoall(
std::vector<at::Tensor>& /* outputTensors */,
std::vector<at::Tensor>& /* inputTensors */,
const AllToAllOptions& opts = AllToAllOptions()) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support alltoall"));
}
virtual void monitoredBarrier(
const BarrierOptions& /* unused */,
bool /* unused */ = false) {
auto backendName = getBackendName();
TORCH_CHECK(
false,
c10::str(
"Backend ",
backendName,
" does not support monitoredBarrier, only GLOO supports monitored barrier."));
}
// Agrees on an initial sequence number for the whole group by having rank 0
// create it and broadcast it to other ranks using the store. Only implemented
// for GLOO and NCCL backends currently.
virtual void setSequenceNumberForGroup() {
auto backendName = getBackendName();
TORCH_CHECK(
false,
c10::str(
"Backend ",
backendName,
" does not yet support sequence numbers."));
}
// Retrieves the current sequence number for the whole group, which should be
// in sync. If the returned number is not consistent across the group, it
// may indicate that there is some sort of collective desynchronization.
virtual uint64_t getSequenceNumberForGroup() {
auto backendName = getBackendName();
TORCH_CHECK(
false,
c10::str(
"Backend ",
backendName,
" does not yet support sequence numbers."));
}
virtual c10::intrusive_ptr<Work> send(
std::vector<at::Tensor>& /* tensors */,
int /* dstRank */,
int /* tag */) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support send"));
}
virtual c10::intrusive_ptr<Work> recv(
std::vector<at::Tensor>& /* tensors */,
int /* srcRank */,
int /* tag */) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support recv"));
}
virtual c10::intrusive_ptr<Work> recvAnysource(
std::vector<at::Tensor>& /* tensors */,
int /* tag */) {
TORCH_CHECK(
false,
c10::str(
"Backend ", getBackendName(), " does not support recvAnysource"));
}
virtual c10::intrusive_ptr<Work> barrier(
const BarrierOptions& /* opts */ = BarrierOptions()) {
TORCH_CHECK(
false,
c10::str("Backend ", getBackendName(), " does not support barrier"));
}
virtual void registerOnCompletionHook(
std::function<void(std::shared_ptr<WorkInfo>)>&& hook) {
TORCH_CHECK(
false,
"Only ProcessGrouppNCCL supports onCompletion hook, but got ",
getBackendName(),
" backend.");
}
virtual void waitForPendingWorks() {
TORCH_CHECK(
false,
"Only ProcessGrouppNCCL supports waitForPendingWorks, but got ",
getBackendName(),
" backend.");
}
virtual void enableCollectivesTiming() {
TORCH_CHECK(
false,
"Backend ",
getBackendName(),
" is missing implementation of enableCollectivesTiming.");
}
bool hasHooks() const {
return onCompletionHook_ != nullptr;
}
// Do not call this directly, use ProcessGroup::setGroupName instead.
void setGroupName(const std::string& name) {
pg_name_ = name;
}
const std::string& getGroupName() const {
return pg_name_;
}
void setGroupDesc(const std::string& desc) {
pg_desc_ = desc;
}
const std::string& getGroupDesc() const {
return pg_desc_;
}
// See similar functions in ProcessGroup.hpp for context.
c10::optional<at::Device> getBoundDeviceId() const {
return bound_device_id_;
}
// Perform an eager connect to the specified device if the backend supports
// it.
virtual void eagerConnectSingleDevice(at::Device device) {
// no-op in the default case; this is an optimization some
// backends may perform
}
void setBoundDeviceId(c10::optional<at::Device> device) {
if (device) {
TORCH_CHECK(device->has_index(), "setBoundDeviceId must have an index");
}
bound_device_id_ = device;
}
protected:
// Implementations of this interface need to call this to setup
// appropriate logging etc.
void init();
const int rank_;
const int size_;
// Debug level setting. It is parsed once when ProcessGroup is constructed and
// remains the same across use of this process group.
DebugLevel dist_debug_level_;
std::string pg_name_;
std::string pg_desc_;
std::function<void(std::shared_ptr<WorkInfo>)> onCompletionHook_;
c10::optional<at::Device> bound_device_id_;
};
} // namespace c10d