set explicit number of threads in every OpenMP parallel region

.ci/lint-cpp.sh

@@ -18,3 +18,28 @@ cmakelint \
     ${cmake_files} \
 || exit -1
 echo "done running cmakelint"
+
+echo "checking that all OpenMP pragmas specify num_threads()"
+get_omp_pragmas_without_num_threads() {
+    grep \
+        -n \
+        -R \
+        --include='*.c' \
+        --include='*.cc' \
+        --include='*.cpp' \
+        --include='*.h' \
+        --include='*.hpp' \
+        'pragma omp parallel' \
+    | grep -v ' num_threads' \
+    | grep -v 'openmp_wrapper.h'
+}
+PROBLEMATIC_LINES=$(
+    get_omp_pragmas_without_num_threads
+)
+if test "${PROBLEMATIC_LINES}" != ""; then
+    get_omp_pragmas_without_num_threads
+    echo "Found '#pragma omp parallel' not using explicit num_threads() configuration. Fix those."
+    echo "For details, see https://www.openmp.org/spec-html/5.0/openmpse14.html#x54-800002.6"
+    exit -1
+fi
+echo "done checking OpenMP pragmas"

R-package/src/lightgbm_R.cpp

@@ -226,7 +226,7 @@ SEXP LGBM_DatasetGetSubset_R(SEXP handle,
   int32_t len = static_cast<int32_t>(Rf_asInteger(len_used_row_indices));
   std::vector<int32_t> idxvec(len);
   // convert from one-based to zero-based index
-#pragma omp parallel for schedule(static, 512) if (len >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (len >= 1024)
   for (int32_t i = 0; i < len; ++i) {
     idxvec[i] = static_cast<int32_t>(INTEGER(used_row_indices)[i] - 1);
   }
@@ -339,7 +339,7 @@ SEXP LGBM_DatasetSetField_R(SEXP handle,
   const char* name = CHAR(PROTECT(Rf_asChar(field_name)));
   if (!strcmp("group", name) || !strcmp("query", name)) {
     std::vector<int32_t> vec(len);
-#pragma omp parallel for schedule(static, 512) if (len >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (len >= 1024)
     for (int i = 0; i < len; ++i) {
       vec[i] = static_cast<int32_t>(INTEGER(field_data)[i]);
     }
@@ -348,7 +348,7 @@ SEXP LGBM_DatasetSetField_R(SEXP handle,
     CHECK_CALL(LGBM_DatasetSetField(R_ExternalPtrAddr(handle), name, REAL(field_data), len, C_API_DTYPE_FLOAT64));
   } else {
     std::vector<float> vec(len);
-#pragma omp parallel for schedule(static, 512) if (len >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (len >= 1024)
     for (int i = 0; i < len; ++i) {
       vec[i] = static_cast<float>(REAL(field_data)[i]);
     }
@@ -372,19 +372,19 @@ SEXP LGBM_DatasetGetField_R(SEXP handle,
   if (!strcmp("group", name) || !strcmp("query", name)) {
     auto p_data = reinterpret_cast<const int32_t*>(res);
     // convert from boundaries to size
-#pragma omp parallel for schedule(static, 512) if (out_len >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (out_len >= 1024)
     for (int i = 0; i < out_len - 1; ++i) {
       INTEGER(field_data)[i] = p_data[i + 1] - p_data[i];
     }
   } else if (!strcmp("init_score", name)) {
     auto p_data = reinterpret_cast<const double*>(res);
-#pragma omp parallel for schedule(static, 512) if (out_len >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (out_len >= 1024)
     for (int i = 0; i < out_len; ++i) {
       REAL(field_data)[i] = p_data[i];
     }
   } else {
     auto p_data = reinterpret_cast<const float*>(res);
-#pragma omp parallel for schedule(static, 512) if (out_len >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (out_len >= 1024)
     for (int i = 0; i < out_len; ++i) {
       REAL(field_data)[i] = p_data[i];
     }
@@ -611,7 +611,7 @@ SEXP LGBM_BoosterUpdateOneIterCustom_R(SEXP handle,
   int is_finished = 0;
   int int_len = Rf_asInteger(len);
   std::vector<float> tgrad(int_len), thess(int_len);
-#pragma omp parallel for schedule(static, 512) if (int_len >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (int_len >= 1024)
   for (int j = 0; j < int_len; ++j) {
     tgrad[j] = static_cast<float>(REAL(grad)[j]);
     thess[j] = static_cast<float>(REAL(hess)[j]);

include/LightGBM/feature_group.h

@@ -361,7 +361,7 @@ class FeatureGroup {
   inline void FinishLoad() {
     if (is_multi_val_) {
       OMP_INIT_EX();
-#pragma omp parallel for schedule(guided)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(guided)
       for (int i = 0; i < num_feature_; ++i) {
         OMP_LOOP_EX_BEGIN();
         multi_bin_data_[i]->FinishLoad();

include/LightGBM/tree.h

@@ -185,7 +185,7 @@ class Tree {
   * \param rate The factor of shrinkage
   */
   virtual inline void Shrinkage(double rate) {
-#pragma omp parallel for schedule(static, 1024) if (num_leaves_ >= 2048)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 1024) if (num_leaves_ >= 2048)
     for (int i = 0; i < num_leaves_ - 1; ++i) {
       leaf_value_[i] = MaybeRoundToZero(leaf_value_[i] * rate);
       internal_value_[i] = MaybeRoundToZero(internal_value_[i] * rate);
@@ -210,15 +210,15 @@ class Tree {
   inline double shrinkage() const { return shrinkage_; }
 
   virtual inline void AddBias(double val) {
-#pragma omp parallel for schedule(static, 1024) if (num_leaves_ >= 2048)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 1024) if (num_leaves_ >= 2048)
     for (int i = 0; i < num_leaves_ - 1; ++i) {
       leaf_value_[i] = MaybeRoundToZero(leaf_value_[i] + val);
       internal_value_[i] = MaybeRoundToZero(internal_value_[i] + val);
     }
     leaf_value_[num_leaves_ - 1] =
         MaybeRoundToZero(leaf_value_[num_leaves_ - 1] + val);
     if (is_linear_) {
-#pragma omp parallel for schedule(static, 1024) if (num_leaves_ >= 2048)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 1024) if (num_leaves_ >= 2048)
       for (int i = 0; i < num_leaves_ - 1; ++i) {
         leaf_const_[i] = MaybeRoundToZero(leaf_const_[i] + val);
       }

include/LightGBM/utils/common.h

@@ -691,7 +691,7 @@ static void ParallelSort(_RanIt _First, _RanIt _Last, _Pr _Pred, _VTRanIt*) {
   size_t inner_size = (len + num_threads - 1) / num_threads;
   inner_size = std::max(inner_size, kMinInnerLen);
   num_threads = static_cast<int>((len + inner_size - 1) / inner_size);
-#pragma omp parallel for schedule(static, 1)
+#pragma omp parallel for num_threads(num_threads) schedule(static, 1)
   for (int i = 0; i < num_threads; ++i) {
     size_t left = inner_size*i;
     size_t right = left + inner_size;
@@ -707,7 +707,7 @@ static void ParallelSort(_RanIt _First, _RanIt _Last, _Pr _Pred, _VTRanIt*) {
   // Recursive merge
   while (s < len) {
     int loop_size = static_cast<int>((len + s * 2 - 1) / (s * 2));
-    #pragma omp parallel for schedule(static, 1)
+    #pragma omp parallel for num_threads(num_threads) schedule(static, 1)
     for (int i = 0; i < loop_size; ++i) {
       size_t left = i * 2 * s;
       size_t mid = left + s;

include/LightGBM/utils/threading.h

@@ -73,7 +73,7 @@ class Threading {
     INDEX_T num_inner = end - start;
     BlockInfo<INDEX_T>(num_inner, min_block_size, &n_block, &num_inner);
     OMP_INIT_EX();
-#pragma omp parallel for schedule(static, 1)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 1)
     for (int i = 0; i < n_block; ++i) {
       OMP_LOOP_EX_BEGIN();
       INDEX_T inner_start = start + num_inner * i;

src/application/application.cpp

@@ -227,7 +227,7 @@ void Application::Predict() {
     TextReader<int> result_reader(config_.output_result.c_str(), false);
     result_reader.ReadAllLines();
     std::vector<std::vector<int>> pred_leaf(result_reader.Lines().size());
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int i = 0; i < static_cast<int>(result_reader.Lines().size()); ++i) {
       pred_leaf[i] = Common::StringToArray<int>(result_reader.Lines()[i], '\t');
       // Free memory

src/application/predictor.hpp

@@ -233,7 +233,7 @@ class Predictor {
       std::vector<std::pair<int, double>> oneline_features;
       std::vector<std::string> result_to_write(lines.size());
       OMP_INIT_EX();
-      #pragma omp parallel for schedule(static) firstprivate(oneline_features)
+      #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static) firstprivate(oneline_features)
       for (data_size_t i = 0; i < static_cast<data_size_t>(lines.size()); ++i) {
         OMP_LOOP_EX_BEGIN();
         oneline_features.clear();

src/boosting/gbdt.cpp

@@ -255,7 +255,7 @@ void GBDT::RefitTree(const std::vector<std::vector<int>>& tree_leaf_prediction)
   std::vector<int> leaf_pred(num_data_);
   if (linear_tree_) {
     std::vector<int> max_leaves_by_thread = std::vector<int>(OMP_NUM_THREADS(), 0);
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int i = 0; i < static_cast<int>(tree_leaf_prediction.size()); ++i) {
       int tid = omp_get_thread_num();
       for (size_t j = 0; j < tree_leaf_prediction[i].size(); ++j) {
@@ -270,7 +270,7 @@ void GBDT::RefitTree(const std::vector<std::vector<int>>& tree_leaf_prediction)
     Boosting();
     for (int tree_id = 0; tree_id < num_tree_per_iteration_; ++tree_id) {
       int model_index = iter * num_tree_per_iteration_ + tree_id;
-      #pragma omp parallel for schedule(static)
+      #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
       for (int i = 0; i < num_data_; ++i) {
         leaf_pred[i] = tree_leaf_prediction[i][model_index];
         CHECK_LT(leaf_pred[i], models_[model_index]->num_leaves());
@@ -348,7 +348,7 @@ bool GBDT::TrainOneIter(const score_t* gradients, const score_t* hessians) {
     if (data_sample_strategy_->IsHessianChange()) {
       // need to copy customized gradients when using GOSS
       int64_t total_size = static_cast<int64_t>(num_data_) * num_tree_per_iteration_;
-      #pragma omp parallel for schedule(static)
+      #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
       for (int64_t i = 0; i < total_size; ++i) {
         gradients_[i] = gradients[i];
         hessians_[i] = hessians[i];
@@ -669,7 +669,7 @@ void GBDT::GetPredictAt(int data_idx, double* out_result, int64_t* out_len) {
   }
   #endif  // USE_CUDA
   if (objective_function_ != nullptr) {
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (data_size_t i = 0; i < num_data; ++i) {
       std::vector<double> tree_pred(num_tree_per_iteration_);
       for (int j = 0; j < num_tree_per_iteration_; ++j) {
@@ -682,7 +682,7 @@ void GBDT::GetPredictAt(int data_idx, double* out_result, int64_t* out_len) {
       }
     }
   } else {
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (data_size_t i = 0; i < num_data; ++i) {
       for (int j = 0; j < num_tree_per_iteration_; ++j) {
         out_result[j * num_data + i] = static_cast<double>(raw_scores[j * num_data + i]);

src/boosting/gbdt.h

@@ -434,7 +434,7 @@ class GBDT : public GBDTBase {
     }
     start_iteration_for_pred_ = start_iteration;
     if (is_pred_contrib) {
-      #pragma omp parallel for schedule(static)
+      #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
       for (int i = 0; i < static_cast<int>(models_.size()); ++i) {
         models_[i]->RecomputeMaxDepth();
       }

src/boosting/gbdt_model_text.cpp

@@ -354,7 +354,7 @@ std::string GBDT::SaveModelToString(int start_iteration, int num_iteration, int
   std::vector<std::string> tree_strs(num_used_model - start_model);
   std::vector<size_t> tree_sizes(num_used_model - start_model);
   // output tree models
-  #pragma omp parallel for schedule(static)
+  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
   for (int i = start_model; i < num_used_model; ++i) {
     const int idx = i - start_model;
     tree_strs[idx] = "Tree=" + std::to_string(idx) + '\n';
@@ -552,7 +552,7 @@ bool GBDT::LoadModelFromString(const char* buffer, size_t len) {
       models_.emplace_back(nullptr);
     }
     OMP_INIT_EX();
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int i = 0; i < num_trees; ++i) {
       OMP_LOOP_EX_BEGIN();
       auto cur_p = p + tree_boundries[i];

src/boosting/rf.hpp

@@ -97,7 +97,7 @@ class RF : public GBDT {
     }
     size_t total_size = static_cast<size_t>(num_data_) * num_tree_per_iteration_;
     std::vector<double> tmp_scores(total_size, 0.0f);
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int j = 0; j < num_tree_per_iteration_; ++j) {
       size_t offset = static_cast<size_t>(j)* num_data_;
       for (data_size_t i = 0; i < num_data_; ++i) {

src/boosting/score_updater.hpp

@@ -39,7 +39,7 @@ class ScoreUpdater {
         Log::Fatal("Number of class for initial score error");
       }
       has_init_score_ = true;
-#pragma omp parallel for schedule(static, 512) if (total_size >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (total_size >= 1024)
       for (int64_t i = 0; i < total_size; ++i) {
         score_[i] = init_score[i];
       }
@@ -54,15 +54,15 @@ class ScoreUpdater {
   virtual inline void AddScore(double val, int cur_tree_id) {
     Common::FunctionTimer fun_timer("ScoreUpdater::AddScore", global_timer);
     const size_t offset = static_cast<size_t>(num_data_) * cur_tree_id;
-#pragma omp parallel for schedule(static, 512) if (num_data_ >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_data_ >= 1024)
     for (int i = 0; i < num_data_; ++i) {
       score_[offset + i] += val;
     }
   }
 
   virtual inline void MultiplyScore(double val, int cur_tree_id) {
     const size_t offset = static_cast<size_t>(num_data_) * cur_tree_id;
-#pragma omp parallel for schedule(static, 512) if (num_data_ >= 1024)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static, 512) if (num_data_ >= 1024)
     for (int i = 0; i < num_data_; ++i) {
       score_[offset + i] *= val;
     }

src/c_api.cpp

@@ -437,7 +437,7 @@ class Booster {
     int64_t num_pred_in_one_row = boosting_->NumPredictOneRow(start_iteration, num_iteration, is_predict_leaf, predict_contrib);
     auto pred_fun = predictor.GetPredictFunction();
     OMP_INIT_EX();
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int i = 0; i < nrow; ++i) {
       OMP_LOOP_EX_BEGIN();
       auto one_row = get_row_fun(i);
@@ -459,7 +459,7 @@ class Booster {
     auto pred_sparse_fun = predictor.GetPredictSparseFunction();
     std::vector<std::vector<std::unordered_map<int, double>>>& agg = *agg_ptr;
     OMP_INIT_EX();
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int64_t i = 0; i < nrow; ++i) {
       OMP_LOOP_EX_BEGIN();
       auto one_row = get_row_fun(i);
@@ -551,7 +551,7 @@ class Booster {
       indptr_index++;
       int64_t matrix_start_index = m * static_cast<int64_t>(agg.size());
       OMP_INIT_EX();
-      #pragma omp parallel for schedule(static)
+      #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
       for (int64_t i = 0; i < static_cast<int64_t>(agg.size()); ++i) {
         OMP_LOOP_EX_BEGIN();
         auto row_vector = agg[i];
@@ -663,7 +663,7 @@ class Booster {
     }
     // Note: we parallelize across matrices instead of rows because of the column_counts[m][col_idx] increment inside the loop
     OMP_INIT_EX();
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int m = 0; m < num_matrices; ++m) {
       OMP_LOOP_EX_BEGIN();
       for (int64_t i = 0; i < static_cast<int64_t>(agg.size()); ++i) {
@@ -1074,7 +1074,7 @@ int LGBM_DatasetPushRows(DatasetHandle dataset,
     p_dataset->ResizeRaw(p_dataset->num_numeric_features() + nrow);
   }
   OMP_INIT_EX();
-  #pragma omp parallel for schedule(static)
+  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
   for (int i = 0; i < nrow; ++i) {
     OMP_LOOP_EX_BEGIN();
     const int tid = omp_get_thread_num();
@@ -1116,7 +1116,7 @@ int LGBM_DatasetPushRowsWithMetadata(DatasetHandle dataset,
   const int max_omp_threads = p_dataset->omp_max_threads() > 0 ? p_dataset->omp_max_threads() : OMP_NUM_THREADS();
 
   OMP_INIT_EX();
-#pragma omp parallel for schedule(static)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
   for (int i = 0; i < nrow; ++i) {
     OMP_LOOP_EX_BEGIN();
     // convert internal thread id to be unique based on external thread id
@@ -1153,7 +1153,7 @@ int LGBM_DatasetPushRowsByCSR(DatasetHandle dataset,
     p_dataset->ResizeRaw(p_dataset->num_numeric_features() + nrow);
   }
   OMP_INIT_EX();
-  #pragma omp parallel for schedule(static)
+  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
   for (int i = 0; i < nrow; ++i) {
     OMP_LOOP_EX_BEGIN();
     const int tid = omp_get_thread_num();
@@ -1199,7 +1199,7 @@ int LGBM_DatasetPushRowsByCSRWithMetadata(DatasetHandle dataset,
   const int max_omp_threads = p_dataset->omp_max_threads() > 0 ? p_dataset->omp_max_threads() : OMP_NUM_THREADS();
 
   OMP_INIT_EX();
-#pragma omp parallel for schedule(static)
+#pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
   for (int i = 0; i < nrow; ++i) {
     OMP_LOOP_EX_BEGIN();
     // convert internal thread id to be unique based on external thread id
@@ -1319,7 +1319,7 @@ int LGBM_DatasetCreateFromMats(int32_t nmat,
   int32_t start_row = 0;
   for (int j = 0; j < nmat; ++j) {
     OMP_INIT_EX();
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int i = 0; i < nrow[j]; ++i) {
       OMP_LOOP_EX_BEGIN();
       const int tid = omp_get_thread_num();
@@ -1394,7 +1394,7 @@ int LGBM_DatasetCreateFromCSR(const void* indptr,
     }
   }
   OMP_INIT_EX();
-  #pragma omp parallel for schedule(static)
+  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
   for (int i = 0; i < nindptr - 1; ++i) {
     OMP_LOOP_EX_BEGIN();
     const int tid = omp_get_thread_num();
@@ -1465,7 +1465,7 @@ int LGBM_DatasetCreateFromCSRFunc(void* get_row_funptr,
 
   OMP_INIT_EX();
   std::vector<std::pair<int, double>> thread_buffer;
-  #pragma omp parallel for schedule(static) private(thread_buffer)
+  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static) private(thread_buffer)
   for (int i = 0; i < num_rows; ++i) {
     OMP_LOOP_EX_BEGIN();
     {
@@ -1506,7 +1506,7 @@ int LGBM_DatasetCreateFromCSC(const void* col_ptr,
     std::vector<std::vector<double>> sample_values(ncol_ptr - 1);
     std::vector<std::vector<int>> sample_idx(ncol_ptr - 1);
     OMP_INIT_EX();
-    #pragma omp parallel for schedule(static)
+    #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
     for (int i = 0; i < static_cast<int>(sample_values.size()); ++i) {
       OMP_LOOP_EX_BEGIN();
       CSC_RowIterator col_it(col_ptr, col_ptr_type, indices, data, data_type, ncol_ptr, nelem, i);
@@ -1534,7 +1534,7 @@ int LGBM_DatasetCreateFromCSC(const void* col_ptr,
       reinterpret_cast<const Dataset*>(reference));
   }
   OMP_INIT_EX();
-  #pragma omp parallel for schedule(static)
+  #pragma omp parallel for num_threads(OMP_NUM_THREADS()) schedule(static)
   for (int i = 0; i < ncol_ptr - 1; ++i) {
     OMP_LOOP_EX_BEGIN();
     const int tid = omp_get_thread_num();