Change reduce operation from thrust to cub. Fix for cuda 9.1 error (#3218)

* Change reduce operation from thrust to cub. Fix for cuda 9.1 runtime error

* Unit test sum reduce

src/common/device_helpers.cuh

@@ -797,6 +797,29 @@ void sumReduction(dh::CubMemory &tmp_mem, dh::dvec<T> &in, dh::dvec<T> &out,
                                        in.data(), out.data(), nVals));
 }
 
+/**
+* @brief Helper function to perform device-wide sum-reduction, returns to the
+* host
+* @param tmp_mem cub temporary memory info
+* @param in the input array to be reduced
+* @param nVals number of elements in the input array
+*/
+template <typename T>
+T sumReduction(dh::CubMemory &tmp_mem, T *in, int nVals) {
+  size_t tmpSize;
+  dh::safe_cuda(cub::DeviceReduce::Sum(nullptr, tmpSize, in, in, nVals));
+  // Allocate small extra memory for the return value
+  tmp_mem.LazyAllocate(tmpSize + sizeof(T));
+  auto ptr = reinterpret_cast<T *>(tmp_mem.d_temp_storage) + 1;
+  dh::safe_cuda(cub::DeviceReduce::Sum(
+    reinterpret_cast<void *>(ptr), tmpSize, in,
+    reinterpret_cast<T *>(tmp_mem.d_temp_storage), nVals));
+  T sum;
+  dh::safe_cuda(cudaMemcpy(&sum, tmp_mem.d_temp_storage, sizeof(T),
+    cudaMemcpyDeviceToHost));
+  return sum;
+}
+
 /**
  * @brief Fill a given constant value across all elements in the buffer
  * @param out the buffer to be filled