Fix compiler warnings. (#8022)

- Remove/fix unused parameters
- Remove deprecated code in rabit.
- Update dmlc-core.

src/tree/gpu_hist/feature_groups.cu

@@ -29,7 +29,7 @@ FeatureGroups::FeatureGroups(const common::HistogramCuts& cuts, bool is_dense,
   bin_segments_h.push_back(0);
 
   const std::vector<uint32_t>& cut_ptrs = cuts.Ptrs();
-  int max_shmem_bins = shm_size / bin_size;
+  size_t max_shmem_bins = shm_size / bin_size;
   max_group_bins = 0;
 
   for (size_t i = 2; i < cut_ptrs.size(); ++i) {

src/tree/gpu_hist/histogram.cu

@@ -188,7 +188,7 @@ void BuildGradientHistogram(EllpackDeviceAccessor const& matrix,
   int device = 0;
   dh::safe_cuda(cudaGetDevice(&device));
   // opt into maximum shared memory for the kernel if necessary
-  int max_shared_memory = dh::MaxSharedMemoryOptin(device);
+  size_t max_shared_memory = dh::MaxSharedMemoryOptin(device);
 
   size_t smem_size = sizeof(typename HistRounding<GradientSumT>::SharedSumT) *
                      feature_groups.max_group_bins;

src/tree/gpu_hist/row_partitioner.cu

@@ -79,6 +79,7 @@ void RowPartitioner::SortPosition(common::Span<bst_node_t> position,
 
 void Reset(int device_idx, common::Span<RowPartitioner::RowIndexT> ridx,
            common::Span<bst_node_t> position) {
+  dh::safe_cuda(cudaSetDevice(device_idx));
   CHECK_EQ(ridx.size(), position.size());
   dh::LaunchN(ridx.size(), [=] __device__(size_t idx) {
     ridx[idx] = idx;
@@ -92,7 +93,7 @@ RowPartitioner::RowPartitioner(int device_idx, size_t num_rows)
   dh::safe_cuda(cudaSetDevice(device_idx_));
   ridx_ = dh::DoubleBuffer<RowIndexT>{&ridx_a_, &ridx_b_};
   position_ = dh::DoubleBuffer<bst_node_t>{&position_a_, &position_b_};
-  ridx_segments_.emplace_back(Segment(0, num_rows));
+  ridx_segments_.emplace_back(static_cast<size_t>(0), num_rows);
 
   Reset(device_idx, ridx_.CurrentSpan(), position_.CurrentSpan());
   left_counts_.resize(256);

src/tree/hist/histogram.h

@@ -140,9 +140,7 @@ class HistogramBuilder {
                                      nodes_for_subtraction_trick,
                                      starting_index, sync_count);
     } else {
-      this->SyncHistogramLocal(p_tree, nodes_for_explicit_hist_build,
-                               nodes_for_subtraction_trick, starting_index,
-                               sync_count);
+      this->SyncHistogramLocal(p_tree, nodes_for_explicit_hist_build, nodes_for_subtraction_trick);
     }
   }
   /** same as the other build hist but handles only single batch data (in-core) */
@@ -211,11 +209,9 @@ class HistogramBuilder {
                             nodes_for_explicit_hist_build, p_tree);
   }
 
-  void SyncHistogramLocal(
-      RegTree *p_tree,
-      std::vector<ExpandEntry> const &nodes_for_explicit_hist_build,
-      std::vector<ExpandEntry> const &nodes_for_subtraction_trick,
-      int starting_index, int sync_count) {
+  void SyncHistogramLocal(RegTree *p_tree,
+                          std::vector<ExpandEntry> const &nodes_for_explicit_hist_build,
+                          std::vector<ExpandEntry> const &nodes_for_subtraction_trick) {
     const size_t nbins = this->builder_.GetNumBins();
     common::BlockedSpace2d space(
         nodes_for_explicit_hist_build.size(), [&](size_t) { return nbins; },

src/tree/param.cc

@@ -92,14 +92,14 @@ void ParseInteractionConstraint(
   for (size_t i = 0; i < all.size(); ++i) {
     auto const &set = get<Array const>(all[i]);
     for (auto const &v : set) {
-      if (XGBOOST_EXPECT(IsA<Integer>(v), true)) {
-        uint32_t u = static_cast<uint32_t const>(get<Integer const>(v));
+      if (XGBOOST_EXPECT(IsA<Integer const>(v), true)) {
+        auto u = static_cast<bst_feature_t>(get<Integer const>(v));
         out[i].emplace_back(u);
       } else if (IsA<Number>(v)) {
         double d = get<Number const>(v);
         CHECK_EQ(std::floor(d), d)
             << "Found floating point number in interaction constraints";
-        out[i].emplace_back(static_cast<uint32_t const>(d));
+        out[i].emplace_back(static_cast<uint32_t>(d));
       } else {
         LOG(FATAL) << "Unknown value type for interaction constraint:"
                    << v.GetValue().TypeStr();

src/tree/tree_model.cc

@@ -354,10 +354,10 @@ class TextGenerator : public TreeGenerator {
 };
 
 XGBOOST_REGISTER_TREE_IO(TextGenerator, "text")
-.describe("Dump text representation of tree")
-.set_body([](FeatureMap const& fmap, std::string const& attrs, bool with_stats) {
-            return new TextGenerator(fmap, with_stats);
-          });
+    .describe("Dump text representation of tree")
+    .set_body([](FeatureMap const& fmap, std::string const& /*attrs*/, bool with_stats) {
+      return new TextGenerator(fmap, with_stats);
+    });
 
 class JsonGenerator : public TreeGenerator {
   using SuperT = TreeGenerator;
@@ -510,10 +510,10 @@ class JsonGenerator : public TreeGenerator {
 };
 
 XGBOOST_REGISTER_TREE_IO(JsonGenerator, "json")
-.describe("Dump json representation of tree")
-.set_body([](FeatureMap const& fmap, std::string const& attrs, bool with_stats) {
-            return new JsonGenerator(fmap, with_stats);
-          });
+    .describe("Dump json representation of tree")
+    .set_body([](FeatureMap const& fmap, std::string const& /*attrs*/, bool with_stats) {
+      return new JsonGenerator(fmap, with_stats);
+    });
 
 struct GraphvizParam : public XGBoostParameter<GraphvizParam> {
   std::string yes_color;

src/tree/updater_colmaker.cc

@@ -98,7 +98,7 @@ class ColMaker: public TreeUpdater {
   }
 
   void Update(HostDeviceVector<GradientPair> *gpair, DMatrix *dmat,
-              common::Span<HostDeviceVector<bst_node_t>> out_position,
+              common::Span<HostDeviceVector<bst_node_t>> /*out_position*/,
               const std::vector<RegTree *> &trees) override {
     if (rabit::IsDistributed()) {
       LOG(FATAL) << "Updater `grow_colmaker` or `exact` tree method doesn't "

src/tree/updater_refresh.cc

@@ -42,7 +42,7 @@ class TreeRefresher : public TreeUpdater {
   }
   // update the tree, do pruning
   void Update(HostDeviceVector<GradientPair> *gpair, DMatrix *p_fmat,
-              common::Span<HostDeviceVector<bst_node_t>> out_position,
+              common::Span<HostDeviceVector<bst_node_t>> /*out_position*/,
               const std::vector<RegTree *> &trees) override {
     if (trees.size() == 0) return;
     const std::vector<GradientPair> &gpair_h = gpair->ConstHostVector();

src/tree/updater_sync.cc

@@ -33,7 +33,7 @@ class TreeSyncher : public TreeUpdater {
   }
 
   void Update(HostDeviceVector<GradientPair>*, DMatrix*,
-              common::Span<HostDeviceVector<bst_node_t>> out_position,
+              common::Span<HostDeviceVector<bst_node_t>> /*out_position*/,
               const std::vector<RegTree*>& trees) override {
     if (rabit::GetWorldSize() == 1) return;
     std::string s_model;