NCCL-based 1-bit Adam + Code Refactor for Comm. Backends (deepspeedai…

…#594)

* NCCL based 1-bit Implementation + Refactor to add communication backends (deepspeedai#593)

* add nccl 1-bit optim.

* temporary commit to save stuff.

* Use dist collectives instead of mpi routines.

* remove old code for comm.

* Fix bugs. still does not work.

* modify to test the nccl side code path

* Initial gather impl. Works intra-node.

* Updates to comm. phase 2. nccl comm. passed the tests.

* refactor code to introduce nccl/mpi as backends for onebit adam.

* Refactor updates to test/engine.

* Fix compile/runtime errors.

* simplify support for nccl/mpi backends.

* Add missign file

* Add compression backend in constructor. Revert later.

* modify test with some perf counting.

* Implement a true non-blocking gather for nccl side.

* Revert "Add compression backend in constructor. Revert later."

This reverts commit df8c40d.

* improve the 1-bit adam test.

* Refactor comm. and compression backend in 1-bit adam.

* Fix the test.

* Fix runtime errors and typos in nccl backend

* fix mpi backend. modify tests.

* modify nccl perf test.

* fix mpi side errors.

* Add an mpi perf test

* Sync DSE.

* Remove old collectives file.

* Undo a typo.

* Graceful failure for torch versions that don't support nccl pt2pt.

deepspeed/runtime/comm/mpi.py

@@ -0,0 +1,299 @@
+'''
+Copyright 2020 The Microsoft DeepSpeed Team
+'''
+
+import torch
+import cupy
+import time
+import numpy as np
+from mpi4py import MPI
+
+from deepspeed.runtime.compression.cupy import CupyBackend
+
+
+class MpiBackend(object):
+    def __init__(self, cuda_aware):
+        self.comm = MPI.COMM_WORLD
+        self.rank = self.comm.Get_rank()
+        self.size = self.comm.Get_size()
+        self.cuda_aware = cuda_aware
+        self.compression_backend = CupyBackend()
+
+    def my_igather(self, rank, size, comm, sendbuf, recbuf, root):
+        req = []
+        if rank == root:
+            for idx in range(size):
+                if idx != rank:
+                    req.append(comm.Irecv(recbuf[idx], source=idx))
+                else:
+                    recbuf[rank] = sendbuf
+        else:
+            req.append(comm.Isend(sendbuf, dest=root))
+        return req
+
+    def gather_cuda(self,
+                    rank,
+                    world_size,
+                    comm,
+                    cupy_sign_list_packed,
+                    cupy_recvbuf_sign,
+                    cupy_worker_scale,
+                    cupy_recvbuf_scale):
+        # We do in-place operations on cupy buffers so we do not return any buffers
+        requests = []
+        for idx in range(world_size):
+            req_sign = self.my_igather(rank,
+                                  world_size,
+                                  comm,
+                                  cupy_sign_list_packed[idx],
+                                  cupy_recvbuf_sign,
+                                  root=idx)
+            requests += req_sign
+
+        for idx in range(world_size):
+            req_scale = self.my_igather(rank,
+                                   world_size,
+                                   comm,
+                                   cupy_worker_scale,
+                                   cupy_recvbuf_scale,
+                                   root=idx)
+            requests += req_scale
+
+        MPI.Request.Waitall(requests)
+
+    def gather_host(self,
+                    rank,
+                    world_size,
+                    comm,
+                    cupy_sign_list_packed,
+                    cupy_recvbuf_sign,
+                    cupy_worker_scale,
+                    cupy_recvbuf_scale):
+
+        # In-place operations are not possible for newly created cupy arrays
+        # so we need to return the new buffers
+        numpy_recvbuf_sign = np.zeros([world_size,
+                                       cupy_sign_list_packed[rank].size],
+                                      dtype=cupy_sign_list_packed[0].dtype)
+        numpy_recvbuf_scale = np.zeros([world_size, 1], dtype=cupy_worker_scale.dtype)
+
+        # 1. convert from cupy to numpy
+        numpy_sign_list_packed = cupy_sign_list_packed
+
+        for idx in range(world_size):
+            numpy_sign_list_packed[idx] = cupy.asnumpy(cupy_sign_list_packed[idx])
+
+        numpy_worker_scale = cupy.asnumpy(cupy_worker_scale)
+        numpy_recvbuf_scale = cupy.asnumpy(cupy_recvbuf_scale)
+
+        cupy.cuda.get_current_stream().synchronize()
+
+        # 2. use numpy buffers for communication
+        requests = []
+
+        for idx in range(world_size):
+            req_sign = self.my_igather(rank,
+                                  world_size,
+                                  comm,
+                                  numpy_sign_list_packed[idx],
+                                  numpy_recvbuf_sign,
+                                  root=idx)
+            requests += req_sign
+
+        for idx in range(world_size):
+            req_scale = self.my_igather(rank,
+                                   world_size,
+                                   comm,
+                                   numpy_worker_scale,
+                                   numpy_recvbuf_scale,
+                                   root=idx)
+            requests += req_scale
+
+        MPI.Request.Waitall(requests)
+
+        # 3. Convert back from numpy to cupy
+        cupy_recvbuf_sign = cupy.asarray(numpy_recvbuf_sign)
+        for idx in range(world_size):
+            cupy_sign_list_packed[idx] = cupy.asarray(numpy_sign_list_packed[idx])
+
+        cupy_worker_scale = cupy.asarray(numpy_worker_scale)
+        cupy_recvbuf_scale = cupy.asarray(numpy_recvbuf_scale)
+        cupy.cuda.get_current_stream().synchronize()
+
+        return cupy_sign_list_packed, cupy_recvbuf_sign, cupy_worker_scale, cupy_recvbuf_scale
+
+    def allgather_cuda(self,
+                       comm,
+                       cupy_server_sign_packed,
+                       cupy_recvbuf_sign_server,
+                       cupy_server_scale,
+                       cupy_recvbuf_scale_server):
+        comm.Allgather(cupy_server_sign_packed, cupy_recvbuf_sign_server)
+        comm.Allgather(cupy_server_scale, cupy_recvbuf_scale_server)
+
+    def allgather_host(self,
+                       comm,
+                       cupy_server_sign_packed,
+                       cupy_recvbuf_sign_server,
+                       cupy_server_scale,
+                       cupy_recvbuf_scale_server):
+
+        # 1. Convert cupy to numpy
+        numpy_recvbuf_sign_server = np.zeros(
+            [comm.Get_size(),
+             cupy_server_sign_packed.size],
+            dtype=cupy_server_sign_packed.dtype)
+        numpy_recvbuf_scale_server = np.zeros([comm.Get_size(),
+                                               1],
+                                              dtype=cupy_server_scale.dtype)
+
+        numpy_server_sign_packed = cupy.asnumpy(cupy_server_sign_packed)
+        numpy_recvbuf_sign_server = cupy.asnumpy(cupy_recvbuf_sign_server)
+        numpy_server_scale = cupy.asnumpy(cupy_server_scale)
+        numpy_recvbuf_scale_server = cupy.asnumpy(cupy_recvbuf_scale_server)
+        cupy.cuda.get_current_stream().synchronize()
+
+        # 2. Communicate numpy buffers
+        comm.Allgather(numpy_server_sign_packed, numpy_recvbuf_sign_server)
+        comm.Allgather(numpy_server_scale, numpy_recvbuf_scale_server)
+        comm.Barrier()
+
+        # 3. Convert numpy back to cupy
+        cupy_server_sign_packed = cupy.asarray(numpy_server_sign_packed)
+        cupy_recvbuf_sign_server = cupy.asarray(numpy_recvbuf_sign_server)
+        cupy_server_scale = cupy.asarray(numpy_server_scale)
+        cupy_recvbuf_scale_server = cupy.asarray(numpy_recvbuf_scale_server)
+        cupy.cuda.get_current_stream().synchronize()
+
+        return cupy_server_sign_packed, cupy_recvbuf_sign_server, cupy_server_scale, cupy_recvbuf_scale_server
+
+    def compressed_allreduce(self,
+                             buffer_m: torch.tensor,
+                             worker_error,
+                             server_error,
+                             local_rank):
+
+        all_start_time = time.time()
+        original_size = buffer_m.numel()
+        cupy.cuda.Device(local_rank).use()
+
+        if torch.numel(buffer_m) != torch.numel(worker_error):
+            empty_tensor = torch.zeros(torch.numel(worker_error) - torch.numel(buffer_m),
+                                       device=buffer_m.device)
+            buffer_m = torch.cat([buffer_m, empty_tensor])
+
+        buffer_m.add_(worker_error)
+        worker_scale = torch.norm(buffer_m) / np.sqrt(torch.numel(buffer_m))
+        sign_buffer_m = buffer_m.sign().add_(1).bool()
+        sign_buffer_m = sign_buffer_m.float()
+        sign_buffer_m.add_(-0.5).mul_(2.0)
+        worker_error.set_((buffer_m - worker_scale * sign_buffer_m))
+        sign_buffer_m = None
+
+        compensated_buffer_m = buffer_m
+        compensated_buffer_m.sign_()
+        compensated_buffer_m = compensated_buffer_m.add_(1).bool()
+        cupy_worker_scale = self.compression_backend.torch2cupy(worker_scale)
+        cupy_compensated_buffer_m = self.compression_backend.torch2cupy(
+            compensated_buffer_m)
+        compensated_buffer_m = None
+
+        cupy_sign_list_packed = self.compression_backend.compress_by_chunk(
+            cupy_compensated_buffer_m,
+            self.size)
+        cupy_compensated_buffer_m = None
+
+        cupy_recvbuf_sign = cupy.zeros(
+            [self.size,
+             cupy_sign_list_packed[self.rank].size],
+            dtype=cupy_sign_list_packed[0].dtype)
+        cupy_recvbuf_scale = cupy.zeros([self.size, 1], dtype=cupy_worker_scale.dtype)
+
+        # Communication Phase 1
+        gather_start = time.time()
+        if self.cuda_aware:
+            self.gather_cuda(self.rank,
+                        self.size,
+                        self.comm,
+                        cupy_sign_list_packed,
+                        cupy_recvbuf_sign,
+                        cupy_worker_scale,
+                        cupy_recvbuf_scale)
+        else:
+            cupy_sign_list_packed, cupy_recvbuf_sign, cupy_worker_scale, cupy_recvbuf_scale = self.gather_host(self.rank,
+               self.size,
+               self.comm,
+               cupy_sign_list_packed,
+               cupy_recvbuf_sign,
+               cupy_worker_scale,
+               cupy_recvbuf_scale)
+        gather_end = time.time()
+
+        cupy_unpacked_sign = (cupy.unpackbits(cupy_recvbuf_sign.flatten())).reshape(
+            self.size,
+            -1)
+        cupy_recvbuf_sign = None
+        unpacked_sign = self.compression_backend.cupy2torch(cupy_unpacked_sign).float()
+        cupy_unpacked_sign = None
+        unpacked_sign = unpacked_sign.add_(-0.5).mul_(2.0)
+        worker_scale = self.compression_backend.cupy2torch(cupy_recvbuf_scale).mul_(
+            1 / self.size)
+        compensated_server_m = unpacked_sign.mul_(worker_scale).sum(0)
+        unpacked_sign = None
+
+        compensated_server_m.add_(server_error)
+        server_scale = torch.norm(compensated_server_m) / np.sqrt(
+            compensated_server_m.numel())
+        sign_server_m = compensated_server_m.sign().add_(1).bool()
+        sign_server_m = sign_server_m.float()
+        sign_server_m.add_(-0.5).mul_(2.0)
+        server_error.set_(compensated_server_m - server_scale * sign_server_m)
+        sign_server_m = None
+
+        compensated_server_m.sign_()
+        compensated_server_m = compensated_server_m.add_(1).bool()
+        cupy_server_scale = self.compression_backend.torch2cupy(server_scale)
+        cupy_compensated_server_m = self.compression_backend.torch2cupy(
+            compensated_server_m)
+        compensated_server_m = None
+
+        cupy_server_sign_packed = self.compression_backend.compress_by_chunk(
+            cupy_compensated_server_m,
+            1)
+
+        cupy_recvbuf_sign_server = cupy.zeros(
+            [self.size,
+             cupy_server_sign_packed[0].size],
+            dtype=cupy_sign_list_packed[0].dtype)
+        cupy_recvbuf_scale_server = cupy.zeros([self.size,
+                                                1],
+                                               dtype=cupy_worker_scale.dtype)
+
+        # Communication Phase 2
+        if self.cuda_aware:
+            self.allgather_cuda(self.comm,
+                           cupy_server_sign_packed[0],
+                           cupy_recvbuf_sign_server,
+                           cupy_server_scale,
+                           cupy_recvbuf_scale_server)
+        else:
+            cupy_server_sign_packed[0], cupy_recvbuf_sign_server, cupy_server_scale, cupy_recvbuf_scale_server = self.allgather_host(self.comm,
+                  cupy_server_sign_packed[0],
+                  cupy_recvbuf_sign_server,
+                  cupy_server_scale,
+                  cupy_recvbuf_scale_server)
+
+        cupy_server_unpacked_sign = (cupy.unpackbits(
+            cupy_recvbuf_sign_server.flatten())).reshape(self.size,
+                                                         -1)
+        cupy_recvbuf_sign_server = None
+
+        server_unpacked_sign = self.compression_backend.cupy2torch(
+            cupy_server_unpacked_sign)
+        cupy_server_unpacked_sign = None
+
+        server_unpacked_sign = server_unpacked_sign.float().add_(-0.5).mul_(2.0)
+        server_scale = self.compression_backend.cupy2torch(cupy_recvbuf_scale_server)
+        buffer_m = server_unpacked_sign.mul_(server_scale).flatten()[0:original_size]
+
+        return buffer_m