[CUDA] Fix row-wise histogram construction with dense data matrix (#5103)

* fix cuda exp with dense row wise

* disable usage of multi val group in cuda exp

src/io/dataset.cpp

@@ -342,7 +342,7 @@ void Dataset::Construct(std::vector<std::unique_ptr<BinMapper>>* bin_mappers,
   auto is_sparse = io_config.is_enable_sparse;
   if (io_config.device_type == std::string("cuda") || io_config.device_type == std::string("cuda_exp")) {
       LGBM_config_::current_device = lgbm_device_cuda;
-      if (io_config.device_type == std::string("cuda") && is_sparse) {
+      if ((io_config.device_type == std::string("cuda") || io_config.device_type == std::string("cuda_exp")) && is_sparse) {
         Log::Warning("Using sparse features with CUDA is currently not supported.");
         is_sparse = false;
       }

src/treelearner/cuda/cuda_histogram_constructor.cu

@@ -283,9 +283,13 @@ void CUDAHistogramConstructor::LaunchConstructHistogramKernelInner0(
     LaunchConstructHistogramKernelInner1<HIST_TYPE, SHARED_HIST_SIZE, BIN_TYPE, uint32_t>(cuda_smaller_leaf_splits, num_data_in_smaller_leaf);
   } else if (cuda_row_data_->row_ptr_bit_type() == 64) {
     LaunchConstructHistogramKernelInner1<HIST_TYPE, SHARED_HIST_SIZE, BIN_TYPE, uint64_t>(cuda_smaller_leaf_splits, num_data_in_smaller_leaf);
+  } else {
+    if (!cuda_row_data_->is_sparse()) {
+      LaunchConstructHistogramKernelInner1<HIST_TYPE, SHARED_HIST_SIZE, BIN_TYPE, uint16_t>(cuda_smaller_leaf_splits, num_data_in_smaller_leaf);
     } else {
       Log::Fatal("Unknown row_ptr_bit_type = %d", cuda_row_data_->row_ptr_bit_type());
     }
+  }
 }
 
 template <typename HIST_TYPE, size_t SHARED_HIST_SIZE, typename BIN_TYPE, typename PTR_TYPE>