add namespace aliases to reduce code

src/metric/survival_metric.cu

@@ -25,6 +25,12 @@
 #include "../common/device_helpers.cuh"
 #endif  // XGBOOST_USE_CUDA || XGBOOST_USE_HIP
 
+#if defined(XGBOOST_USE_HIP)
+namespace thrust {
+    namespace cuda = thrust::hip;
+}
+#endif
+
 using AFTParam = xgboost::common::AFTParam;
 using ProbabilityDistributionType = xgboost::common::ProbabilityDistributionType;
 template <typename Distribution>
@@ -103,7 +109,6 @@ class ElementWiseSurvivalMetricsReduction {
 
     dh::XGBCachingDeviceAllocator<char> alloc;
 
-#if defined(XGBOOST_USE_CUDA)
     PackedReduceResult result = thrust::transform_reduce(
       thrust::cuda::par(alloc),
       begin, end,
@@ -118,22 +123,6 @@ class ElementWiseSurvivalMetricsReduction {
       },
       PackedReduceResult(),
       thrust::plus<PackedReduceResult>());
-#elif defined(XGBOOST_USE_HIP)
-    PackedReduceResult result = thrust::transform_reduce(
-      thrust::hip::par(alloc),
-      begin, end,
-      [=] XGBOOST_DEVICE(size_t idx) {
-        double weight = is_null_weight ? 1.0 : static_cast<double>(s_weights[idx]);
-        double residue = d_policy.EvalRow(
-            static_cast<double>(s_label_lower_bound[idx]),
-            static_cast<double>(s_label_upper_bound[idx]),
-            static_cast<double>(s_preds[idx]));
-        residue *= weight;
-        return PackedReduceResult{residue, weight};
-      },
-      PackedReduceResult(),
-      thrust::plus<PackedReduceResult>());
-#endif
 
     return result;
   }