add warp size

src/tree/gpu_hist/evaluate_splits.cu

@@ -18,6 +18,12 @@
 #include "evaluate_splits.cuh"
 #include "expand_entry.cuh"
 
+#if defined(XGBOOST_USE_HIP)
+#define WARP_SIZE WAVEFRONT_SIZE
+#elif defined(XGBOOST_USE_CUDA)
+#define WARP_SIZE 32
+#endif
+
 namespace xgboost {
 #if defined(XGBOOST_USE_HIP)
 namespace cub = hipcub;
@@ -97,11 +103,7 @@ class EvaluateSplitAgent {
         param(shared_inputs.param), evaluator(evaluator),
         missing(parent_sum - ReduceFeature()) {
     static_assert(
-#if defined(XGBOOST_USE_HIP)
-        kBlockSize == WAVEFRONT_SIZE,
-#elif defined(XGBOOST_USE_CUDA)
-        kBlockSize == 32,
-#endif
+        kBlockSize == WARP_SIZE,
         "This kernel relies on the assumption block_size == warp_size");
     // There should be no missing value gradients for a dense matrix
     KERNEL_CHECK(!shared_inputs.is_dense || missing.GetQuantisedHess() == 0);
@@ -393,11 +395,7 @@ void GPUHistEvaluator::LaunchEvaluateSplits(
       combined_num_features, DeviceSplitCandidate());
 
   // One block for each feature
-#if defined(XGBOOST_USE_HIP)
-  uint32_t constexpr kBlockThreads = WAVEFRONT_SIZE;
-#elif defined(XGBOOST_USE_CUDA)
-  uint32_t constexpr kBlockThreads = 32;
-#endif
+  uint32_t constexpr kBlockThreads = WARP_SIZE;
   dh::LaunchKernel {static_cast<uint32_t>(combined_num_features), kBlockThreads,
                     0}(
       EvaluateSplitsKernel<kBlockThreads>, max_active_features, d_inputs,