User specified backend (#35745)

paddle/fluid/framework/fleet/gloo_wrapper.h

@@ -238,6 +238,24 @@ class GlooWrapper {
     return ret;
   }
 
+  // TODO(xiongkun03): support all gather array of
+  //                   numbers with different length
+  //                   can use AllgathervOptions, may be work in different
+  //                   occasion. Need some survey.
+  template <typename T>
+  void AllGatherVector(T* input_ptr, T* output_ptr,
+                       size_t element_num) {  // NOLINT
+    CHECK_EQ(is_initialized_, true);
+#ifdef PADDLE_WITH_GLOO
+    gloo::AllgatherOptions opts(context_);
+    opts.setInput(input_ptr, element_num);
+    opts.setOutput(output_ptr, element_num * size_);
+    gloo::allgather(opts);
+#else
+    LOG(WARNING) << "AllGather does nothing when WITH_GLOO=OFF";
+#endif
+  }
+
  protected:
   bool is_initialized_ = false;
 #ifdef PADDLE_WITH_GLOO

paddle/fluid/imperative/gloo_context.cc

@@ -18,6 +18,7 @@
 #include "paddle/fluid/platform/device_context.h"
 #include "paddle/fluid/platform/place.h"
 #include "paddle/fluid/string/split.h"
+#include "paddle/fluid/string/string_helper.h"
 
 namespace paddle {
 namespace framework {
@@ -67,8 +68,36 @@ void GLOOParallelContext::AllReduceByStream(const framework::Variable &src,
                                             framework::Variable *dst,
                                             int ring_id, bool use_calc_stream) {
   // AllReduce(src, dst, strategy_, ring_id, use_calc_stream);
-  auto src_tensor = src.Get<framework::LoDTensor>();
-  auto *dst_tensor = dst->GetMutable<framework::LoDTensor>();
+  if (src.IsType<framework::LoDTensor>()) {
+    if (!dst->IsType<framework::LoDTensor>()) {
+      dst->Clear();
+    }
+    AllReduce(src.Get<framework::LoDTensor>(),
+              dst->GetMutable<framework::LoDTensor>());
+  } else if (src.IsType<framework::SelectedRows>()) {
+    if (&src != dst) {
+      if (!dst->IsType<framework::SelectedRows>()) {
+        dst->Clear();
+      }
+      AllReduce(src.Get<framework::SelectedRows>(),
+                dst->GetMutable<framework::SelectedRows>());
+    } else {
+      // SelectedRows cannot be allreduce in-place
+      framework::Variable tmp_dst;
+      AllReduce(src.Get<framework::SelectedRows>(),
+                tmp_dst.GetMutable<framework::SelectedRows>());
+      *dst = std::move(tmp_dst);
+    }
+  } else {
+    PADDLE_THROW(platform::errors::InvalidArgument(
+        "Unsupported variable type %s for imperative allreduce, only "
+        "LoDTensor and SelectedRows are supported.",
+        platform::demangle(framework::ToTypeName(src.Type()))));
+  }
+}
+
+void GLOOParallelContext::AllReduce(const framework::Tensor &src_tensor,
+                                    framework::Tensor *dst_tensor) {
   auto gloo_wrapper = framework::GlooWrapper::GetInstance();
   dst_tensor->Resize(src_tensor.dims());
   switch (src_tensor.type()) {
@@ -84,6 +113,88 @@ void GLOOParallelContext::AllReduceByStream(const framework::Variable &src,
   gloo_wrapper->Barrier();
 }
 
+#define GLOO_ALL_GATHER_CASE(type, T, gw)                         \
+  case type: {                                                    \
+    const auto *src_tensor_ptr = src_tensor.data<T>();            \
+    gw->AllGatherVector<T>(const_cast<T *>(src_tensor_ptr),       \
+                           reinterpret_cast<T *>(dst_tensor_ptr), \
+                           value_sendcount);                      \
+    break;                                                        \
+  }
+
+void GLOOParallelContext::AllReduce(const framework::SelectedRows &src,
+                                    framework::SelectedRows *dst) {
+  // auto ;
+  // int local_rank = strategy_.local_rank_;
+  int nranks = strategy_.nranks_;
+  VLOG(3) << "SelectedRows AllReduce start";
+  const auto &src_tensor = src.value();
+  const auto &place = src_tensor.place();
+  auto dtype = src_tensor.type();
+  // 1. Gather rows number from all workers. Here use ncclAllGather to do this,
+  // but we can use other ways to implement is in the future
+  const auto &src_rows = src.rows();
+  auto gloo_wrapper = framework::GlooWrapper::GetInstance();
+  size_t local_row_num = src_rows.size();
+  std::vector<size_t> rows_num_vector =
+      gloo_wrapper->AllGather<size_t>(local_row_num);
+  const auto *cpu_rows_num_ptr = rows_num_vector.data();
+  auto rows_num = std::accumulate(cpu_rows_num_ptr, cpu_rows_num_ptr + nranks,
+                                  static_cast<int64_t>(0));
+  dst->set_height(src.height());
+  VLOG(3) << "Gather rows: " << string::join_strings(rows_num_vector, ',')
+          << ", total rows number: " << rows_num
+          << ", height: " << src.height();
+  auto *dst_rows = dst->mutable_rows();
+  dst_rows->resize(rows_num);
+  auto *dst_rows_ptr = dst_rows->MutableData(place);
+  const int64_t *src_rows_ptr = src_rows.Data(place);
+
+  // VLOG(3) << "Selected Rows of src:" << string::join_strings(dst_rows, ',')
+
+  auto *dst_tensor = dst->mutable_value();
+  auto dims = src_tensor.dims();
+  dims[0] = rows_num;
+  auto feature_size = framework::product(dims) / dims[0];
+  dst_tensor->Resize(dims);
+  if (std::all_of(cpu_rows_num_ptr, cpu_rows_num_ptr + nranks,
+                  [&](size_t row) { return row == cpu_rows_num_ptr[0]; })) {
+    // During sparse communication, the number of each card is same.
+    // Because gloo wrapper utility class currently don't support
+    // broadcast, so we only deal the-same case.
+    VLOG(3) << "Use the gloo all reduce to sync. SRC:" << src_tensor;
+    // framework::SerializeToStream(VLOG(4), src);
+    VLOG(3) << "allgather replaces broadcast to speed up in sparse allreduce";
+    auto value_sendcount = cpu_rows_num_ptr[0] * feature_size;
+    auto *dst_tensor_ptr = dst_tensor->mutable_data(place, dtype);
+
+    gloo_wrapper->AllGatherVector<int64_t>(const_cast<int64_t *>(src_rows_ptr),
+                                           static_cast<int64_t *>(dst_rows_ptr),
+                                           rows_num_vector[0]);
+
+    switch (dtype) {
+      GLOO_ALL_GATHER_CASE(framework::proto::VarType::FP32, float,
+                           gloo_wrapper);
+      GLOO_ALL_GATHER_CASE(framework::proto::VarType::FP64, double,
+                           gloo_wrapper);
+      GLOO_ALL_GATHER_CASE(framework::proto::VarType::INT32, int, gloo_wrapper);
+      GLOO_ALL_GATHER_CASE(framework::proto::VarType::INT64, int64_t,
+                           gloo_wrapper);
+      default: {
+        PADDLE_THROW(platform::errors::InvalidArgument(
+            "Invalid datatype for allreduce"));
+      }
+    }
+    VLOG(3) << "Selected Row DST:" << *dst_tensor;
+    VLOG(3) << "Selected Rows of DST:"
+            << string::join_strings(std::vector<int64_t>(*dst_rows), ',');
+  } else {
+    PADDLE_THROW(platform::errors::InvalidArgument(
+        "The number of each card is not the same, gloo only support the-same"
+        "batch division"));
+  }
+}
+
 paddle::platform::DeviceContext *GLOOParallelContext::GetDeviceContext(
     int ring_id) {
   // return the CPUDeviceContext

paddle/fluid/imperative/gloo_context.h

@@ -16,6 +16,9 @@
 #include <memory>
 #include <string>
 #include <vector>
+#include "paddle/fluid/framework/scope.h"
+#include "paddle/fluid/framework/selected_rows.h"
+#include "paddle/fluid/framework/variable.h"
 #include "paddle/fluid/imperative/parallel_context.h"
 #include "paddle/fluid/platform/device_context.h"
 
@@ -52,6 +55,11 @@ class GLOOParallelContext : public ParallelContext {
 
   void SynchronizeCompute() override;
 
+ private:
+  void AllReduce(const framework::Tensor& src, framework::Tensor* dst);
+  void AllReduce(const framework::SelectedRows& src,
+                 framework::SelectedRows* dst);
+
  private:
   std::unique_ptr<platform::CPUDeviceContext> device_;
 };

python/paddle/distributed/fleet/launch.py

@@ -103,7 +103,12 @@ see: http://www.paddlepaddle.org/documentation/docs/zh/1.6/user_guides/howto/tra
         type=str,
         default="log",
         help="The path for each process's log. Default --log_dir=log/")
-
+    base_group.add_argument(
+        "--backend",
+        type=str,
+        default="auto",
+        help="Specifize the backend, can be gloo|nccl|bkcl|auto. Default value is auto which perfers nccl or bkcl."
+    )
     base_group.add_argument(
         "--nproc_per_node",
         type=int,
@@ -230,8 +235,21 @@ def get_cluster_from_args(args, device_mode, devices_per_proc):
                        devices_per_proc)
 
 
+def cpuonly_check(args):
+    if args.ips and len(args.ips.split(',')) > 1:
+        raise RuntimeError(
+            "CPUONLY launch only support single trainer, that is len(ips)=1, but got %s."
+            % args.ips)
+    if args.run_mode:
+        assert args.run_mode == 'cpuonly', "CPUONLY launch only support run mode is CPUONLY"
+    if args.servers:
+        raise RuntimeError("CPUONLY launch can't have --servers as arguments.")
+    return True
+
+
 def launch_collective(args):
     # parse arguments, used for cloud-single-machine and local
+    if args.backend == 'gloo': cpuonly_check(args)
     (device_mode, devices_per_proc) = launch_utils.get_device_proc_info(args)
     trainers_num = cloud_utils.get_trainers_num()
     logger.debug("parsed from args trainerss_num:{} mode:{} devices:{}".format(
@@ -265,6 +283,7 @@ def launch_collective(args):
     global_envs["PADDLE_WITH_GLOO"] = str(os.getenv("PADDLE_WITH_GLOO", "0"))
     global_envs["PADDLE_GLOO_RENDEZVOUS"] = "3"
     global_envs["PADDLE_GLOO_FS_PATH"] = gloo_rendezvous_dir
+    global_envs["PADDLE_DISTRI_BACKEND"] = args.backend
 
     procs = start_local_trainers(
         cluster,
@@ -349,9 +368,12 @@ def which_distributed_mode(args):
 
     if fluid.core.is_compiled_with_cuda():
         accelerators = fluid.core.get_cuda_device_count()
+        args.backend = 'nccl'
     elif fluid.core.is_compiled_with_npu():
+        args.backend = 'unknown'
         accelerators = fluid.core.get_npu_device_count()
     elif fluid.core.is_compiled_with_xpu():
+        args.backend = 'bkcl'
         accelerators = fluid.core.get_xpu_device_count()
     else:
         accelerators = 0
@@ -372,10 +394,14 @@ def which_distributed_mode(args):
     else:
         if not fluid.core.is_compiled_with_cuda(
         ) and not fluid.core.is_compiled_with_xpu():
-            logger.warning(
-                "Not found distinct arguments and not compiled with cuda or xpu. Default use ps mode"
-            )
-            return DistributeMode.PS
+            if args.servers:
+                logger.warning(
+                    "Not found distinct arguments and not compiled with cuda or xpu. \
+But found args.servers not empty, default use ps mode")
+                return DistributeMode.PS
+            else:
+                args.backend = "gloo"
+                return DistributeMode.COLLECTIVE
         else:
             logger.warning(
                 "Not found distinct arguments and compiled with cuda or xpu. Default use collective mode"
@@ -556,7 +582,20 @@ def launch():
     logger = get_logger()
     _print_arguments(args)
 
-    distribute_mode = which_distributed_mode(args)
+    if args.backend == 'auto':
+        distribute_mode = which_distributed_mode(args)
+        assert args.backend in [
+            'gloo', 'nccl', 'bkcl', 'unknown'
+        ]  # which_distributed_mode must modify args.backend
+    else:
+        assert args.run_mode == 'collective' or args.run_mode == None, "When backend is not 'auto', run mode must be collective"
+        check_backend(args.backend)
+        distribute_mode = DistributeMode.COLLECTIVE
+
+    block_windows_and_macos(
+        args.backend)  # raise error when using gloo on windows or macos
+    if args.backend == 'gloo':
+        logger.warning("launch start with CPUONLY mode")
 
     if enable_elastic(args, distribute_mode):
         launch_elastic(args, distribute_mode)

python/paddle/distributed/fleet/launch_utils.py

@@ -22,6 +22,7 @@ import subprocess
 import tempfile
 import shutil
 from contextlib import closing
+import multiprocessing
 import socket
 import warnings
 import six
@@ -30,6 +31,7 @@ import struct
 import paddle
 import paddle.fluid as fluid
 from distutils.util import strtobool
+import paddle.utils.cpp_extension.extension_utils as utils
 logger = logging.getLogger("root")
 logger.propagate = False
 
@@ -669,29 +671,31 @@ def get_xpus(xpus):
     return res_xpus
 
 
-def get_device_mode():
+def get_device_mode(backend):
     if fluid.core.is_compiled_with_npu() and \
             fluid.core.get_npu_device_count() > 0:
         print("launch train in ascend npu mode!")
         return DeviceMode.ASCEND_NPU
 
-    if fluid.core.is_compiled_with_cuda() and \
+    if backend == 'nccl' and \
             fluid.core.get_cuda_device_count() > 0:
         print("launch train in GPU mode!")
         return DeviceMode.GPU
 
-    if fluid.core.is_compiled_with_xpu() and fluid.core.get_xpu_device_count(
-    ) > 0:
+    if backend == 'bkcl' and fluid.core.get_xpu_device_count() > 0:
         print("launch train in XPU mode")
         return DeviceMode.XPU
 
-    print("launch train in CPU mode")
-    return DeviceMode.CPU
+    if backend == 'gloo':
+        print("launch train in CPU mode")
+        return DeviceMode.CPU
+
+    raise RuntimeError("Don't supported devices")
 
 
 def get_device_proc_info(args):
     # device_mode
-    device_mode = get_device_mode()
+    device_mode = get_device_mode(args.backend)
 
     # devices
     devices_per_proc = []
@@ -722,6 +726,9 @@ def get_device_proc_info(args):
         else:
             devices_per_proc = xpus
     elif device_mode == DeviceMode.CPU:
+        if hasattr(args, "paddle_cpuonly") and args.nproc_per_node is None:
+            #NOTE (xiongkun03) set it to cpu core number
+            args.nproc_per_node = multiprocessing.cpu_count()
         if args.nproc_per_node is None:
             devices_per_proc = [0]
         else:
@@ -1237,3 +1244,45 @@ class ParameterServerLauncher(object):
             tp.cmd = cmd
 
             self.procs["heter_worker"].append(tp)
+
+
+def check_backend(backend):
+    if backend not in ['nccl', 'gloo', 'bkcl', 'auto']:
+        raise ValueError(
+            "paddle.distributed initialize error, "
+            "backend argument can only be one of 'nccl', 'gloo', 'bkcl', 'auto', but got %s"
+            % backend)
+
+    if backend == 'nccl' and not fluid.core.is_compiled_with_cuda():
+        raise ValueError(
+            "paddle.distributed initialize error, "
+            "your paddle is not compiled with cuda but you assign 'nccl' as backend."
+        )
+
+    if backend == 'bkcl' and not fluid.core.is_compiled_with_xpu():
+        raise ValueError(
+            "paddle.distributed initialize error, "
+            "your paddle is not compiled with xpu but you assign 'bkcl' as backend."
+        )
+
+
+def block_windows_and_macos(backend):
+    if backend != 'gloo': return
+    if utils.OS_NAME.startswith('darwin'):  # MACOS , block
+        raise ValueError(
+            "You are going to using gloo on macos, but currently is not supported"
+        )
+    if utils.IS_WINDOWS:  # MACOS , block
+        raise ValueError(
+            "You are going to using gloo on windows, but currently is not supported"
+        )
+
+
+def get_backend_by_compile_flag():
+    if fluid.core.is_compiled_with_cuda():
+        return 'nccl'
+
+    if fluid.core.is_compiled_with_xpu():
+        return 'bkcl'
+
+    return 'gloo'

python/paddle/distributed/parallel.py

@@ -26,6 +26,7 @@ from paddle import compat as cpt
 from paddle.fluid import core
 from paddle.fluid.framework import _set_expected_place
 from paddle.fluid.dygraph import parallel_helper
+from paddle.distributed.fleet.launch_utils import check_backend
 from paddle.fluid.dygraph.parallel import ParallelEnv
 from paddle.distributed.fleet.base.private_helper_function import wait_server_ready  # noqa: F401
 
@@ -55,25 +56,8 @@ def _start_kv_server(port, http_server_d, size):
     http_server.stop()
 
 
-def _check_backend(backend):
-    if backend not in ['nccl', 'gloo', 'bkcl', 'auto']:
-        raise ValueError(
-            "paddle.distributed initialize error, "
-            "backend argument can only be one of 'nccl', 'gloo', 'bkcl', 'auto', but got %s"
-            % backend)
-
-    if backend == 'nccl' and not core.is_compiled_with_cuda():
-        raise ValueError(
-            "paddle.distributed initialize error, "
-            "your paddle is not compiled with cuda but you assign 'nccl' as backend."
-        )
-
-    if backend == 'bkcl' and not core.is_compiled_with_xpu():
-        raise ValueError(
-            "paddle.distributed initialize error, "
-            "your paddle is not compiled with xpu but you assign 'bkcl' as backend."
-        )
-
+def _is_cpuonly(backend):
+    check_backend(backend)
     if backend in ['auto', 'nccl', 'bkcl'] and (core.is_compiled_with_cuda() or
                                                 core.is_compiled_with_xpu()):
         # passes 'auto' and can use cuda or xpu, use the default logics. so return False
@@ -82,7 +66,7 @@ def _check_backend(backend):
         return True
 
 
-def init_parallel_env(backend='auto'):
+def init_parallel_env():
     """
     Initialize parallel training environment in dynamic graph mode.
 
@@ -154,7 +138,8 @@ def init_parallel_env(backend='auto'):
         return
     # NOTE(xiongkun): support cpu gloo only, add this environment variable to 
     #                 enable cpu only gloo prarllel training)
-    is_cpu_only = _check_backend(backend)
+    backend = os.environ.get('PADDLE_DISTRI_BACKEND', 'auto')
+    is_cpu_only = _is_cpuonly(backend)
     # 1. gpu xpu check, must be gpu or xpu, 
     if not (is_cpu_only or core.is_compiled_with_cuda() or
             core.is_compiled_with_xpu()):

python/paddle/distributed/spawn.py

@@ -24,8 +24,10 @@ import warnings
 from paddle.distributed.utils import _print_arguments
 from paddle.distributed.utils import _prepare_trainer_env
 from paddle.distributed.utils import get_host_name_ip
-from paddle.distributed.cloud_utils import get_cluster_and_pod
+from paddle.distributed.cloud_utils import get_cluster_and_pod, _get_trainers_num
+from paddle.distributed.fleet.launch import get_cluster_from_args
 from paddle.distributed.fleet.cloud_utils import use_paddlecloud
+from paddle.distributed.fleet.launch_utils import DeviceMode, check_backend, block_windows_and_macos
 from paddle.device import get_device
 
 # deprecated module import
@@ -71,7 +73,9 @@ def _py_supported_check():
 
 def _options_valid_check(options):
     # `print_config` keeped as a debug options, not show to users
-    supported_options = ['start_method', 'ips', 'gpus', 'xpus', 'print_config']
+    supported_options = [
+        'start_method', 'ips', 'gpus', 'xpus', 'print_config', 'backend'
+    ]
     deprecated_options = [
         'selected_devices', 'started_port', 'cluster_node_ips', 'node_ip',
         'use_paddlecloud'
@@ -95,6 +99,22 @@ def _get_default_nprocs():
         return core.get_cuda_device_count()
     elif 'xpu' in device:
         return core.get_xpu_device_count()
+    elif 'cpu' in device:
+        return multiprocessing.cpu_count()
+    else:
+        raise RuntimeError(
+            "`paddle.distributed.spawn` does not support parallel training on device `{}` now.".
+            format(device))
+
+
+def _get_default_backend():
+    device = get_device()
+    if 'gpu' in device:
+        return 'nccl'
+    elif 'xpu' in device:
+        return 'bkcl'
+    elif 'cpu' in device:
+        return 'gloo'
     else:
         raise RuntimeError(
             "`paddle.distributed.spawn` does not support parallel training on device `{}` now.".
@@ -112,6 +132,16 @@ def _get_node_ip(ips):
 
 
 def _get_subprocess_env_list(nprocs, options):
+    # NOTE (xiongkun03) Why put backend deduction  here ? 
+    # Becase _get_subprocess_env_list is used by many testcases. 
+    # So for campability, we put backend deduction here 
+
+    # logic for handle backend option
+    if 'backend' not in options or options['backend'] == 'auto':
+        options['backend'] = _get_default_backend()
+    check_backend(options['backend'])
+    block_windows_and_macos(options['backend'])
+
     # contruct processes env list
     processes_env_list = []
 
@@ -133,7 +163,7 @@ def _get_subprocess_env_list(nprocs, options):
     # if we set FLAGS_selected_gpus or FLAGS_selected_xpus to be `0,1,2,3`, it may cause error
     # when using `ParallelEnv`
     # NOTE(chenweihang): use absolute gpu or xpu card id
-    if core.is_compiled_with_cuda():
+    if options['backend'] == 'nccl':
         args.selected_devices = options.get('gpus', None)
         if args.selected_devices is None:
             args.selected_devices = options.get('selected_devices', None)
@@ -168,7 +198,7 @@ def _get_subprocess_env_list(nprocs, options):
                                      "CUDA_VISIBLE_DEVICES (%s)." %
                                      (card_id, ",".join(env_devices_list)))
 
-    elif core.is_compiled_with_xpu():
+    elif options['backend'] == 'bkcl':
         args.selected_devices = options.get('xpus', None)
         if args.selected_devices is None:
             args.selected_devices = options.get('selected_devices', None)
@@ -202,6 +232,23 @@ def _get_subprocess_env_list(nprocs, options):
                     raise ValueError("The selected xpu card %s cannot found in "
                                      "XPU_VISIBLE_DEVICES (%s)." %
                                      (card_id, ",".join(env_devices_list)))
+    elif options['backend'] == 'gloo':
+        # TODO check gpu / xpu flag must not exist
+        warnings.warn(
+            "Your model will be trained under CPUONLY mode by using GLOO,"
+            "because CPUPlace is specified manually or your installed PaddlePaddle only support CPU Device."
+        )
+        args.paddle_cpuonly = True
+        args.selected_devices = None
+        args.ips = args.cluster_node_ips
+        assert options.get(
+            'use_paddlecloud',
+            None) is None, "CPUONLY spawn doesn't support use paddle cloud"
+        assert len(
+            args.cluster_node_ips.split(',')
+        ) <= 1, "CPUONLY spawn only support single trainer, that is len(ips)=1, but got %s."
+        assert _get_trainers_num(
+        ) == 1, "CPUONLY spawn doesn't support multi-trainer"
 
     # set other inner args
     args.node_ip = options.get('node_ip', None)
@@ -215,11 +262,17 @@ def _get_subprocess_env_list(nprocs, options):
         args.use_paddlecloud = use_paddlecloud()
 
     # get cluster and pod config
-    cluster, pod = get_cluster_and_pod(args)
+    if options['backend'] == 'gloo':
+        devices_per_proc = [x for x in range(0, nprocs)]
+        cluster, pod = get_cluster_from_args(args, DeviceMode.CPU,
+                                             devices_per_proc)
+    else:
+        cluster, pod = get_cluster_and_pod(args)
 
     # prepare subprocess env list
     for trainer in pod.trainers:
-        processes_env_list.append(_prepare_trainer_env(cluster, trainer))
+        processes_env_list.append(
+            _prepare_trainer_env(cluster, trainer, options['backend']))
 
     # [Debug] print config
     args.print_config = options.get('print_config', False)
@@ -236,27 +289,35 @@ def _remove_risky_env():
     os.environ.pop("https_proxy", None)
 
 
-def _set_trainer_env(env_dict):
+def _set_trainer_env(env_dict, backend):
     # NOTE(chenweihang): [ Why need set FLAGS_selected_gpus or FLAGS_selected_xpus here? ]
     # When the child process starts, it will inherit the configuration of the 
     # main process and set the FLAGS once, but the environment variable has 
     # not been set at this time, which leads to the FLAGS_selected_gpus or FLAGS_selected_xpus
     # is keep same with mainprocess(usually empty), so manually update the flags here
-    if core.is_compiled_with_cuda():
+
+    # NOTE(xiongkun): why put backend here?  because if gloo, we shouldn't set FLAGS_selectedXXX
+    #
+
+    if backend == 'nccl':
         set_flags({'FLAGS_selected_gpus': env_dict['FLAGS_selected_gpus']})
-    elif core.is_compiled_with_xpu():
+    elif backend == 'bkcl':
         set_flags({'FLAGS_selected_xpus': env_dict['FLAGS_selected_xpus']})
     else:
-        raise ValueError("PaddlePaddle should be compiled with XPU or CUDA.")
+        #NOTE(xiongkun) why not raise Error ? 
+        # So far, we added support for CPU parallel, and will be applied when paddle is not 
+        # compiled with cuda or xp. just do nothing.
+        pass
+
     for var_name in env_dict:
         os.environ[var_name] = env_dict[var_name]
 
 
-def _func_wrapper(func, args, error_queue, return_queue, env_dict):
+def _func_wrapper(func, args, error_queue, return_queue, env_dict, backend):
     try:
         # config subprocess environment variables
         _remove_risky_env()
-        _set_trainer_env(env_dict)
+        _set_trainer_env(env_dict, backend)
         # execute function
         result = func(*args)
         # record function return value
@@ -487,7 +548,8 @@ def spawn(func, args=(), nprocs=-1, join=True, daemon=False, **options):
         return_queue = mp.SimpleQueue()
         process = mp.Process(
             target=_func_wrapper,
-            args=(func, args, error_queue, return_queue, procs_env_list[i]))
+            args=(func, args, error_queue, return_queue, procs_env_list[i],
+                  options['backend']))
         process.daemon = daemon
         process.start()
         error_queues.append(error_queue)

python/paddle/distributed/utils.py

@@ -25,6 +25,7 @@ import subprocess
 from contextlib import closing
 import socket
 from paddle.fluid import core
+from paddle.distributed.fleet.launch_utils import get_backend_by_compile_flag
 from distutils.util import strtobool
 
 from paddle.fluid.layer_helper import LayerHelper
@@ -613,8 +614,10 @@ def find_free_ports(num):
     return None
 
 
-def _prepare_trainer_env(cluster, trainer):
-    if core.is_compiled_with_xpu():
+def _prepare_trainer_env(cluster, trainer, backend=None):
+    if backend is None:
+        backend = get_backend_by_compile_flag()  # for compatibility
+    if backend == 'bkcl':
         proc_env = {
             "FLAGS_selected_xpus":
             "%s" % ",".join([str(g) for g in trainer.gpus]),
@@ -623,7 +626,7 @@ def _prepare_trainer_env(cluster, trainer):
             "PADDLE_TRAINERS_NUM": "%d" % cluster.trainers_nranks(),
             "PADDLE_TRAINER_ENDPOINTS": ",".join(cluster.trainers_endpoints())
         }
-    elif core.is_compiled_with_cuda():
+    elif backend == 'nccl':
         proc_env = {
             "FLAGS_selected_gpus":
             "%s" % ",".join([str(g) for g in trainer.gpus]),
@@ -632,6 +635,19 @@ def _prepare_trainer_env(cluster, trainer):
             "PADDLE_TRAINERS_NUM": "%d" % cluster.trainers_nranks(),
             "PADDLE_TRAINER_ENDPOINTS": ",".join(cluster.trainers_endpoints())
         }
+    elif backend == 'gloo':
+        # NOTE (xiongkun) default fall back into cpu only
+        proc_env = {
+            "PADDLE_TRAINER_ID": "%d" % trainer.rank,
+            "PADDLE_CURRENT_ENDPOINT": "%s" % trainer.endpoint,
+            "PADDLE_TRAINERS_NUM": "%d" % cluster.trainers_nranks(),
+            "PADDLE_TRAINER_ENDPOINTS": ",".join(cluster.trainers_endpoints()),
+            "PADDLE_DISTRI_BACKEND":
+            backend,  # only add here, other will be auto
+        }
+    else:
+        raise ValueError("backend must be one of 'gloo, nccl, bkcl'")
+
     return proc_env
 
 

python/paddle/fluid/tests/unittests/CMakeLists.txt

@@ -200,8 +200,14 @@ endif()
 
 list(REMOVE_ITEM TEST_OPS test_parallel_dygraph_hybrid_parallel)
 
+LIST(REMOVE_ITEM TEST_OPS test_parallel_dygraph_transformer_gloo) # NOTE: @xiongkun03, cpu is too slow, fix it in next PR
+
 if (NOT WITH_GLOO)
     LIST(REMOVE_ITEM TEST_OPS test_parallel_dygraph_dataparallel_cpuonly)
+
+    LIST(REMOVE_ITEM TEST_OPS test_parallel_dygraph_unused_variables_gloo)
+    LIST(REMOVE_ITEM TEST_OPS test_parallel_dygraph_sparse_embedding_over_height_gloo)
+    LIST(REMOVE_ITEM TEST_OPS test_parallel_dygraph_sparse_embedding_gloo)
 endif()
 
 if ((NOT WITH_GPU) AND (NOT WITH_ROCM))
@@ -491,6 +497,10 @@ if (APPLE OR WIN32)
   list(REMOVE_ITEM TEST_OPS test_multiprocess_dataloader_dataset)
 endif()
 
+if (NOT WITH_GLOO)
+    LIST(REMOVE_ITEM TEST_OPS test_cpuonly_spawn)
+endif()
+
 if(NOT WITH_GPU OR WIN32 OR APPLE)
   list(REMOVE_ITEM TEST_OPS test_build_strategy_fusion_group_pass)
 endif()
@@ -654,6 +664,9 @@ if(WITH_DISTRIBUTE)
         endforeach(TEST_OP)
         # solve it later.
         bash_test_modules(test_fleet_launch_ps START_BASH test_fleet_launch_ps.sh SERIAL LABELS "RUN_TYPE=EXCLUSIVE" ENVS "PADDLE_DIST_UT_PORT=${dist_ut_port}" PADDLE_BINARY_DIR=${PADDLE_BINARY_DIR} )
+        if (WITH_GLOO)
+            bash_test_modules(test_cpuonly_launch START_BASH test_cpuonly_launch.sh SERIAL LABELS "RUN_TYPE=EXCLUSIVE" ENVS "PADDLE_DIST_UT_PORT=${dist_ut_port}" PADDLE_BINARY_DIR=${PADDLE_BINARY_DIR} )
+        endif()
         bash_test_modules(test_new_group START_BASH test_new_group.sh SERIAL LABELS "RUN_TYPE=EXCLUSIVE" ENVS "PADDLE_DIST_UT_PORT=${dist_ut_port}+20" PADDLE_BINARY_DIR=${PADDLE_BINARY_DIR} )
     endif(NOT APPLE)
 endif()
@@ -1070,3 +1083,8 @@ set_tests_properties(test_inplace_addto_strategy PROPERTIES TIMEOUT 120)
 set_tests_properties(test_eigvals_op PROPERTIES TIMEOUT 400)
 set_tests_properties(test_tensordot PROPERTIES TIMEOUT 1000)
 set_tests_properties(test_tensordot PROPERTIES LABELS "RUN_TYPE=NIGHTLY")
+if (WITH_GLOO)
+    set_tests_properties(test_parallel_dygraph_unused_variables_gloo PROPERTIES TIMEOUT 120)
+    set_tests_properties(test_parallel_dygraph_sparse_embedding_gloo PROPERTIES TIMEOUT 120)
+    set_tests_properties(test_parallel_dygraph_sparse_embedding_over_height_gloo PROPERTIES TIMEOUT 120)
+endif()

python/paddle/fluid/tests/unittests/parallel_dygraph_gradient_check.py

@@ -66,8 +66,7 @@ class SimpleNet(fluid.Layer):
 
 class TestDistTraning(unittest.TestCase):
     def test_multiple_gpus(self):
-        backend = os.environ.get('PADDLE_DISTRI_BACKEND', 'auto')
-        dist.init_parallel_env(backend)
+        dist.init_parallel_env()
         self.trainer_id = dist.get_rank()
 
         model_a = SimpleNet(self.trainer_id)

python/paddle/fluid/tests/unittests/parallel_dygraph_se_resnext.py

@@ -324,6 +324,7 @@ class TestSeResNeXt(TestParallelDyGraphRunnerBase):
         bs = len(data)
         dy_x_data = np.array([x[0].reshape(3, 224, 224)
                               for x in data]).astype('float32')
+        dy_x_data = dy_x_data / 255.0
         y_data = np.array([x[1] for x in data]).astype('int64').reshape(bs, 1)
         img = to_variable(dy_x_data)
         label = to_variable(y_data)

python/paddle/fluid/tests/unittests/test_cpuonly_launch.sh

+#!/bin/bash
+
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#     http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+function test_launch_cpuonly(){
+    python -m paddle.distributed.launch --nproc_per_node=4 --backend=gloo \
+        parallel_dygraph_gradient_check.py 2>ut.elog
+    if grep -q "ABORT" ut.elog; then
+        echo "test cpu only failed"
+        exit -1
+    else
+        if grep -q "CPUONLY" ut.elog; then
+            echo "test_launch_cpuonly successfully"
+        else 
+            echo "test_launch_cpuonly failed"
+            exit -1
+        fi
+    fi
+}
+function test_launch_error_case1(){
+    python -m paddle.distributed.launch --nproc_per_node=4 --backend=random_str \
+        parallel_dygraph_gradient_check.py 2>ut.elog
+    if grep -q "ValueError" ut.elog; then
+        echo "test_launch_error_case1 successfully"
+    else
+        exit -1
+    fi
+}
+
+test_launch_cpuonly
+test_launch_error_case1

python/paddle/fluid/tests/unittests/test_cpuonly_spawn.py

+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#     http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+import unittest
+
+import paddle
+import paddle.nn as nn
+import paddle.optimizer as opt
+import paddle.distributed as dist
+
+
+class LinearNet(nn.Layer):
+    def __init__(self):
+        super(LinearNet, self).__init__()
+        self._linear1 = nn.Linear(10, 10)
+        self._linear2 = nn.Linear(10, 1)
+
+    def forward(self, x):
+        return self._linear2(self._linear1(x))
+
+
+def train(print_result=False):
+    # 1. initialize parallel environment
+    dist.init_parallel_env()
+
+    # 2. create data parallel layer & optimizer
+    layer = LinearNet()
+    dp_layer = paddle.DataParallel(layer)
+
+    loss_fn = nn.MSELoss()
+    adam = opt.Adam(learning_rate=0.001, parameters=dp_layer.parameters())
+
+    # 3. run layer
+    inputs = paddle.randn([10, 10], 'float32')
+    outputs = dp_layer(inputs)
+    labels = paddle.randn([10, 1], 'float32')
+    loss = loss_fn(outputs, labels)
+
+    if print_result is True:
+        print("loss:", loss.numpy())
+
+    loss.backward()
+    print("Grad is", layer._linear1.weight.grad)
+    adam.step()
+    adam.clear_grad()
+
+
+class TestSpawn(unittest.TestCase):
+    def test_spawn(self):
+        dist.spawn(train, backend='gloo', nprocs=4)
+
+    def test_wrong_backend(self):
+        try:
+            dist.spawn(train, backend='something', nprocs=4)
+        except ValueError as e:
+            self.assertEqual(type(e), ValueError)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/paddle/fluid/tests/unittests/test_dist_base.py

@@ -209,7 +209,11 @@ class TestDistRunnerBase(object):
 
         def get_data():
             origin_batch = next(reader_generator)
-            if args.update_method != "local" and args.use_reader_alloc:
+            if paddle.distributed.get_world_size(
+            ) == 1 and args.update_method == 'gloo':  # Gloo single mode
+                return origin_batch
+
+            elif args.update_method != "local" and args.use_reader_alloc:
                 new_batch = []
                 for offset, item in enumerate(origin_batch):
                     if offset % 2 == args.trainer_id:
@@ -506,7 +510,10 @@ class TestParallelDyGraphRunnerBase(object):
             "train_one_loop should be implemented by the child classes.")
 
     def _get_data(self, batch, args):
-        if args.update_method != "local":
+        if paddle.distributed.get_world_size(
+        ) == 1 and args.update_method == 'gloo':  # Gloo single mode
+            return batch
+        elif args.update_method != "local":
             new_batch = []
             for offset, item in enumerate(batch):
                 if offset % 2 == args.trainer_id:
@@ -518,14 +525,16 @@ class TestParallelDyGraphRunnerBase(object):
     def run_trainer(self, args):
 
         seed = 90
-        if fluid.core.is_compiled_with_cuda():
+        if args.update_method == 'gloo':
+            place = fluid.CPUPlace()
+        elif fluid.core.is_compiled_with_cuda():
             device_id = int(os.getenv("FLAGS_selected_gpus", "0"))
             place = fluid.CUDAPlace(device_id)
         elif fluid.core.is_compiled_with_xpu():
             device_id = int(os.getenv("FLAGS_selected_xpus", "0"))
             place = fluid.XPUPlace(device_id)
         else:
-            assert ("Only support CUDAPlace or XPUPlace for now.")
+            assert ("Only support CUDAPlace or XPUPlace or CPU(Gloo) for now.")
 
         with fluid.dygraph.guard(place):
             fluid.default_startup_program().random_seed = seed
@@ -554,6 +563,16 @@ class TestParallelDyGraphRunnerBase(object):
                     model = dygraph.parallel.DataParallel(
                         model, strategy, find_unused_parameters=True)
                 print_to_err(type(self).__name__, "model built in dygraph")
+
+            elif args.update_method == "gloo":
+                paddle.distributed.init_parallel_env()
+                if not args.find_unused_parameters:
+                    model = dygraph.parallel.DataParallel(
+                        model, find_unused_parameters=False)
+                else:
+                    model = dygraph.parallel.DataParallel(
+                        model, find_unused_parameters=True)
+
             out_losses = []
             print_to_err(type(self).__name__, "begin to run dygraph training")
             for step_id, data in enumerate(train_reader()):
@@ -588,12 +607,12 @@ class TestParallelDyGraphRunnerBase(object):
         args.trainer_id = paddle.distributed.get_rank()
 
         # 3. init parallel env
-        if args.update_method == "nccl2":
+        if args.update_method in ["nccl2", "gloo"]:
             paddle.distributed.init_parallel_env()
 
         # 4. train model
         model, train_reader, opt = self.get_model()
-        if args.update_method == "nccl2":
+        if args.update_method in ["nccl2", "gloo"]:
             if args.find_unused_parameters:
                 model = paddle.DataParallel(model, find_unused_parameters=True)
             else:
@@ -668,7 +687,9 @@ def runtime_main(test_class):
         '--update_method',
         type=str,
         default="local",
-        choices=["pserver", "nccl2", "bkcl", "local", "nccl2_reduce_layer"])
+        choices=[
+            "pserver", "nccl2", "bkcl", "local", "nccl2_reduce_layer", "gloo"
+        ])
     parser.add_argument('--trainer_id', type=int, required=False, default=0)
     parser.add_argument('--trainers', type=int, required=False, default=1)
     parser.add_argument('--nccl_comm_num', type=int, required=False, default=1)
@@ -685,6 +706,7 @@ def runtime_main(test_class):
         '--current_endpoint', type=str, required=False, default="")
     parser.add_argument('--sync_mode', action='store_true')
     parser.add_argument('--use_cuda', action='store_true')
+    parser.add_argument('--use_cpu', action='store_true')
     parser.add_argument('--use_xpu', action='store_true')
     parser.add_argument('--use_dgc', action='store_true')
     parser.add_argument('--accumulate_gradient', action='store_true')
@@ -713,6 +735,9 @@ def runtime_main(test_class):
 
     args = parser.parse_args()
 
+    if args.update_method == 'gloo':
+        paddle.set_device("cpu")
+
     model = test_class()
     if args.role == "pserver" and args.update_method == "pserver":
         model.run_pserver(args)
@@ -770,6 +795,7 @@ class TestDistBase(unittest.TestCase):
         self._use_reader_alloc = True
         self._nccl2_mode = False
         self._bkcl_mode = False
+        self._gloo_mode = False  # now, support gloo backend
         self._pipeline_mode = False
         self._mp_mode = False
         # FIXME(typhoonzero): I added this stupid argument to enable
@@ -875,7 +901,7 @@ class TestDistBase(unittest.TestCase):
                    batch_size=DEFAULT_BATCH_SIZE,
                    batch_merge_repeat=1,
                    log_name="",
-                   devices="0"):
+                   devices="1"):
 
         cmd = self._python_interp
 
@@ -947,6 +973,21 @@ class TestDistBase(unittest.TestCase):
 
         return pickle.loads(local_out)
 
+    def _run_local_gloo(self,
+                        model,
+                        envs,
+                        check_error_log=False,
+                        batch_size=DEFAULT_BATCH_SIZE,
+                        batch_merge_repeat=1,
+                        log_name="",
+                        devices="0"):
+        saved_endpoints = self._ps_endpoints
+        self._ps_endpoints = self._ps_endpoints.split(',')[0]
+        result = self._run_cluster_gloo(model, envs, 'gloo', check_error_log,
+                                        log_name)
+        self._ps_endpoints = saved_endpoints
+        return result
+
     def _run_cluster(self, model, envs, check_error_log, log_name):
         # Run dist train to compare with local results
         ps0, ps1, ps0_pipe, ps1_pipe = self.start_pserver(
@@ -1037,6 +1078,62 @@ class TestDistBase(unittest.TestCase):
 
         return pickle.loads(tr0_out), pickle.loads(tr1_out)
 
+    def _get_gloo_trainer_cmd(self, model, ep, update_method, trainer_id,
+                              trainer_num):
+        env = {}
+        tr_cmd = "%s -u"
+
+        if os.getenv('WITH_COVERAGE', 'OFF') == 'ON':
+            tr_cmd += " -m coverage run --branch -p"
+
+        tr_cmd += " %s --role trainer --endpoints %s --trainer_id %d --current_endpoint %s --update_method %s --lr %f"
+
+        tr_cmd = tr_cmd % \
+                 (self._python_interp, model, self._ps_endpoints,
+                  trainer_id, ep, update_method, self._lr)
+
+        if self._use_reduce:
+            tr_cmd += " --use_reduce"
+        if self._use_reader_alloc:
+            tr_cmd += " --use_reader_alloc"
+        #assert self._use_reduce == False, "gloo not support _use_reduce"
+        #assert self._use_reader_alloc == False, "gloo not support _use_reduce"
+        if self._save_model:
+            tr_cmd += " --save_model"
+        self.__use_cuda = False
+        self.__use_xpu = False
+        assert self.__use_cuda == False, "gloo not support use cuda"
+        assert self.__use_xpu == False, "gloo not support use xpu"
+        tr_cmd += " --use_cpu"
+        env.update({
+            "PADDLE_TRAINERS_NUM": "{}".format(trainer_num),
+            "PADDLE_TRAINER_ID": "{}".format(trainer_id),
+            "PADDLE_TRAINER_ENDPOINTS": self._ps_endpoints,
+            "PADDLE_CURRENT_ENDPOINT": ep,
+            "PADDLE_CURRENT_ENDPOINT": ep,
+            "PADDLE_DISTRI_BACKEND": "gloo",
+            "GLOG_v": "2",
+        })
+
+        assert self._use_dgc == False, "gloo not support use dgc"
+        if self._accumulate_gradient:
+            tr_cmd += " --accumulate_gradient"
+
+        if self._find_unused_parameters:
+            tr_cmd += " --find_unused_parameters"
+
+        assert self._pipeline_mode == False, "gloo not support use pipeline"
+
+        if self._enable_backward_deps:  # build strategy, save it
+            tr_cmd += " --enable_backward_deps"
+
+        if self._fuse_all_reduce is not None:
+            tr_cmd += " --fuse_all_reduce {}".format(self._fuse_all_reduce)
+
+        assert self._use_fleet_api == False, "gloo not support use fleet api"
+        assert self._use_fleet_api_20 == False, "gloo not support use fleet api"
+        return tr_cmd, env
+
     def _get_nccl2_trainer_cmd(self, model, ep, update_method, trainer_id,
                                trainer_num):
         env = {}
@@ -1123,6 +1220,57 @@ class TestDistBase(unittest.TestCase):
 
         return tr_cmd, env
 
+    def _run_cluster_gloo(self, model, envs, update_method, check_error_log,
+                          log_name):
+        assert update_method == "gloo", "_run_cluster_gloo must have update_method: gloo, but get %s" % update_method
+        assert not self._use_hallreduce, "_run_cluster_gloo must have _use_hallreduce = false"
+
+        worker_endpoints = self._ps_endpoints.split(",")
+
+        trainer_num = len(worker_endpoints)
+
+        procs = []
+        pipes = []
+        for i in range(0, trainer_num):
+            tr_cmd, tr_env = self._get_gloo_trainer_cmd(
+                model, worker_endpoints[i], update_method, i, trainer_num)
+            tr_env.update(envs)
+            tr_env["GLOG_vmodule"] = 'gloo_context=4'
+            tr_env["GLOG_v"] = '3'
+            print("use_hallreduce:{} tr_cmd:{}, env: {}".format(
+                self._use_hallreduce, tr_cmd, tr_env))
+
+            tr_pipe = open(log_name + "_tr{}_err.log".format(i), "wb")
+
+            print_to_err(
+                type(self).__name__,
+                "going to start process {} with nccl2".format(i))
+            tr_proc = subprocess.Popen(
+                tr_cmd.strip().split(" "),
+                stdout=subprocess.PIPE,
+                stderr=tr_pipe,
+                env=tr_env)
+
+            procs.append(tr_proc)
+            pipes.append(tr_pipe)
+
+        outs = []
+        for i in range(0, trainer_num):
+            tr_out, tr_err = procs[i].communicate()
+            outs.append(tr_out)
+            pipes[i].close()
+            sys.stderr.write('trainer {} stderr: {}\n'.format(i, tr_err))
+
+        if trainer_num == 1:
+            if check_error_log: print("outs[0]:", outs[0])
+            return pickle.loads(outs[0])
+
+        else:
+            if check_error_log:
+                print("outs[0]:", outs[0])
+                print("outs[1]:", outs[1])
+            return pickle.loads(outs[0]), pickle.loads(outs[1])
+
     def _run_cluster_nccl2(self, model, envs, update_method, check_error_log,
                            log_name):
         if self._use_hallreduce:
@@ -1262,7 +1410,12 @@ class TestDistBase(unittest.TestCase):
 
         required_envs = self._get_required_envs(check_error_log, need_envs)
 
-        local_losses \
+        if self._gloo_mode:
+            local_losses \
+                = self._run_local_gloo(model_file, required_envs,
+                                  check_error_log, log_name=log_name)
+        else:
+            local_losses \
             = self._run_local(model_file, required_envs,
                               check_error_log, log_name=log_name)
 
@@ -1288,6 +1441,14 @@ class TestDistBase(unittest.TestCase):
                 update_method='bkcl',
                 check_error_log=check_error_log,
                 log_name=log_name)
+        elif self._gloo_mode:
+            # gloo mode, cpu only parallel train @xiongkun03
+            tr0_losses, tr1_losses = self._run_cluster_gloo(
+                model_file,
+                required_envs,
+                update_method='gloo',
+                check_error_log=check_error_log,
+                log_name=log_name)
 
         elif self._pipeline_mode:
             tr0_losses, tr1_losses = self._run_pipeline(

python/paddle/fluid/tests/unittests/test_parallel_dygraph_dataparallel.py

@@ -49,6 +49,51 @@ def get_gpus(selected_gpus):
     return selected_gpus
 
 
+def start_local_trainers_cpu(trainer_endpoints,
+                             training_script,
+                             training_script_args,
+                             log_dir=None):
+    current_env = copy.copy(os.environ.copy())
+    current_env.pop("http_proxy", None)
+    current_env.pop("https_proxy", None)
+
+    procs = []
+    n_rank = len(trainer_endpoints)
+    print(trainer_endpoints)
+    for rank_id, endpoint in enumerate(trainer_endpoints):
+        proc_env = {
+            "PADDLE_DISTRI_BACKEND": "gloo",
+            "PADDLE_TRAINER_ID": "%d" % rank_id,
+            "PADDLE_CURRENT_ENDPOINT": "%s" % endpoint,
+            "PADDLE_TRAINERS_NUM": "%d" % n_rank,
+            "PADDLE_TRAINER_ENDPOINTS": ",".join(trainer_endpoints)
+        }
+
+        current_env.update(proc_env)
+
+        print("trainer proc env:{}".format(current_env))
+
+        assert os.getenv('WITH_COVERAGE',
+                         'OFF') == 'OFF', "Gloo don't support WITH_COVERAGE."
+        cmd = "python -u " + training_script
+
+        print("start trainer proc:{} env:{}".format(cmd, proc_env))
+
+        fn = None
+
+        proc = subprocess.Popen(cmd.split(" "), env=current_env)
+
+        tp = TrainerProc()
+        tp.proc = proc
+        tp.rank = rank_id
+        tp.log_fn = fn
+        tp.cmd = cmd
+
+        procs.append(tp)
+
+    return procs
+
+
 def start_local_trainers(cluster,
                          pod,
                          training_script,
@@ -116,6 +161,26 @@ class TestMultipleGpus(unittest.TestCase):
             training_script=target_file_name,
             training_script_args=[])
 
+        while True:
+            alive = watch_local_trainers(procs, cluster.trainers_endpoints())
+
+            if not alive:
+                print("Local procs complete, POD info:{}".format(pod))
+                break
+            time.sleep(3)
+
+
+class TestMultipleWithGloo(unittest.TestCase):
+    def run_mnist_2cpu(self, target_file_name):
+
+        cluster, pod = get_cluster_from_args(
+            [0, 1])  #tmp use. for getting trainer_nranks()
+
+        procs = start_local_trainers_cpu(
+            cluster.trainers_endpoints(),
+            training_script=target_file_name,
+            training_script_args=[])
+
         while True:
             alive = watch_local_trainers(procs, cluster.trainers_nranks())
 

python/paddle/fluid/tests/unittests/test_parallel_dygraph_sparse_embedding_gloo.py

+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import os
+import sys
+import unittest
+
+import paddle.fluid as fluid
+from test_dist_base import TestDistBase
+from spawn_runner_base import TestDistSpawnRunner
+from parallel_dygraph_sparse_embedding import TestSparseEmbedding
+from parallel_dygraph_sparse_embedding_fp64 import TestSparseEmbeddingFP64
+
+flag_name = os.path.splitext(__file__)[0]
+
+
+class TestParallelDygraphSparseEmdedding_GLOO(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._gloo_mode = True
+        self._dygraph = True
+
+    def test_sparse_embedding(self):
+        self.check_with_place(
+            "parallel_dygraph_sparse_embedding.py",
+            delta=1e-5,
+            check_error_log=True,
+            log_name=flag_name)
+
+
+class TestParallelDygraphSparseEmdeddingFP64_GLOO(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._gloo_mode = True
+        self._dygraph = True
+
+    def test_sparse_embedding_fp64(self):
+        self.check_with_place(
+            "parallel_dygraph_sparse_embedding_fp64.py",
+            delta=1e-5,
+            check_error_log=True,
+            log_name=flag_name)
+
+
+if __name__ == "__main__":
+    unittest.main()

python/paddle/fluid/tests/unittests/test_parallel_dygraph_sparse_embedding_over_height_gloo.py

+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import os
+import sys
+import unittest
+
+import paddle.fluid as fluid
+from test_dist_base import TestDistBase
+from spawn_runner_base import TestDistSpawnRunner
+from parallel_dygraph_sparse_embedding_over_height import TestSparseEmbeddingOverHeight
+
+flag_name = os.path.splitext(__file__)[0]
+
+
+class TestParallelDygraphSparseEmdeddingOverHeight_GLOO(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._gloo_mode = True
+        self._dygraph = True
+
+    def test_sparse_embedding(self):
+        self.check_with_place(
+            "parallel_dygraph_sparse_embedding_over_height.py",
+            delta=1e-7,
+            check_error_log=True,
+            log_name=flag_name)
+
+
+if __name__ == "__main__":
+    unittest.main()

python/paddle/fluid/tests/unittests/test_parallel_dygraph_transformer_gloo.py

+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import os
+import sys
+import unittest
+
+import paddle.fluid as fluid
+from test_dist_base import TestDistBase
+from spawn_runner_base import TestDistSpawnRunner
+from parallel_dygraph_transformer import TestTransformer
+
+flag_name = os.path.splitext(__file__)[0]
+
+
+class TestParallelDygraphTransformer_GLOO(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._gloo_mode = True
+        self._dygraph = True
+
+    def test_transformer(self):
+        self.check_with_place(
+            "parallel_dygraph_transformer.py",
+            delta=1e-5,
+            check_error_log=True,
+            log_name=flag_name)
+
+
+class TestParallelDygraphTransformerAccGrad_GLOO(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._gloo_mode = True
+        self._dygraph = True
+        self._accumulate_gradient = True
+        self._find_unused_parameters = False
+
+    def test_transformer(self):
+        if fluid.core.is_compiled_with_cuda():
+            self.check_with_place(
+                "parallel_dygraph_transformer.py",
+                delta=1e-5,
+                check_error_log=True,
+                log_name=flag_name)
+
+
+if __name__ == "__main__":
+    unittest.main()

python/paddle/fluid/tests/unittests/test_parallel_dygraph_unused_variables_gloo.py

+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import os
+import sys
+import unittest
+
+import paddle.fluid as fluid
+from test_dist_base import TestDistBase
+from spawn_runner_base import TestDistSpawnRunner
+from parallel_dygraph_unused_variables import TestSparseEmbeddingUnusedVars
+
+flag_name = os.path.splitext(__file__)[0]
+
+
+class TestParallelDygraphUnusedVar_GLOO(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._gloo_mode = True
+        self._dygraph = True
+
+    def test_net(self):
+        self.check_with_place(
+            "parallel_dygraph_unused_variables.py",
+            delta=1e-5,
+            check_error_log=True,
+            log_name=flag_name)
+
+
+class TestParallelDygraphNoVar_GLOO(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._gloo_mode = True
+        self._dygraph = True
+
+    def test_net(self):
+        self.check_with_place(
+            "parallel_dygraph_none_var.py",
+            delta=1e-5,
+            check_error_log=True,
+            log_name=flag_name)
+
+
+class TestParallelDygraphSharedUnusedVariables_GLOO(TestDistBase):
+    def _setup_config(self):
+        self._sync_mode = False
+        self._gloo_mode = True
+        self._dygraph = True
+
+    def test_mnist(self):
+        self.check_with_place(
+            "parallel_dygraph_shared_unused_var.py",
+            delta=1e-5,
+            check_error_log=True,
+            log_name=flag_name)
+
+
+if __name__ == "__main__":
+    unittest.main()

python/paddle/fluid/tests/unittests/test_spawn_and_init_parallel_env.py

@@ -24,6 +24,7 @@ from paddle.distributed.spawn import _get_subprocess_env_list, _options_valid_ch
 
 from paddle.fluid import core
 from paddle.fluid.dygraph import parallel_helper
+import multiprocessing
 
 # NOTE(chenweihang): Coverage CI is currently not able to count python3
 # unittest, so the unittests here covers some cases that will only be 
@@ -89,8 +90,8 @@ class TestSpawnAssistMethod(unittest.TestCase):
 
     def test_get_default_nprocs(self):
         paddle.set_device('cpu')
-        with self.assertRaises(RuntimeError):
-            nprocs = _get_default_nprocs()
+        nprocs = _get_default_nprocs()
+        self.assertEqual(nprocs, multiprocessing.cpu_count())
 
         paddle.set_device('gpu')
         nprocs = _get_default_nprocs()