Refactor device communicator to make allreduce more flexible (#9295)

tests/cpp/collective/test_nccl_device_communicator.cu

@@ -8,6 +8,7 @@
 #include <string>  // for string
 
 #include "../../../src/collective/nccl_device_communicator.cuh"
+#include "../../../src/collective/communicator-inl.cuh"
 
 namespace xgboost {
 namespace collective {

tests/cpp/common/test_quantile.cu

@@ -1,7 +1,7 @@
 #include <gtest/gtest.h>
 #include "test_quantile.h"
 #include "../helpers.h"
-#include "../../../src/collective/device_communicator.cuh"
+#include "../../../src/collective/communicator-inl.cuh"
 #include "../../../src/common/hist_util.cuh"
 #include "../../../src/common/quantile.cuh"
 
@@ -464,10 +464,9 @@ void TestSameOnAllWorkers(std::int32_t n_gpus) {
     thrust::copy(thrust::device, local_data.data(),
                  local_data.data() + local_data.size(),
                  all_workers.begin() + local_data.size() * rank);
-    collective::DeviceCommunicator* communicator = collective::Communicator::GetDevice(device);
-
-    communicator->AllReduceSum(all_workers.data().get(), all_workers.size());
-    communicator->Synchronize();
+    collective::AllReduce<collective::Operation::kSum>(device, all_workers.data().get(),
+                                                       all_workers.size());
+    collective::Synchronize(device);
 
     auto base_line = dh::ToSpan(all_workers).subspan(0, size_as_float);
     std::vector<float> h_base_line(base_line.size());

tests/cpp/plugin/test_federated_adapter.cu

@@ -36,7 +36,7 @@ TEST_F(FederatedAdapterTest, DeviceAllReduceSum) {
       int count = 3;
       thrust::device_vector<double> buffer(count, 0);
       thrust::sequence(buffer.begin(), buffer.end());
-      adapter.AllReduceSum(buffer.data().get(), count);
+      adapter.AllReduce(buffer.data().get(), count, DataType::kDouble, Operation::kSum);
       thrust::host_vector<double> host_buffer = buffer;
       EXPECT_EQ(host_buffer.size(), count);
       for (auto i = 0; i < count; i++) {