Optimization of loading chunks by sorting BlocksInChunks first

Author: Martin Foll

tmva/tmva/inc/TMVA/BatchGenerator/RChunkLoader.hxx

@@ -350,6 +350,12 @@ public:
          // fill a chunk by looping over the blocks in a chunk (see RChunkConstructor)
          std::size_t chunkEntry = 0;
          std::vector<std::pair<Long_t, Long_t>> BlocksInChunk = fTraining->ChunksIntervals[chunk];
+
+         std::sort(BlocksInChunk.begin(), BlocksInChunk.end(),
+                   [](const std::pair<Long_t, Long_t>& a, const std::pair<Long_t, Long_t>& b) {
+                      return a.first < b.first;
+                   });
+         
          for (std::size_t i = 0; i < BlocksInChunk.size(); i++) {
 
             // Use the block start and end entry to load into the chunk if the dataframe is not filtered
@@ -416,6 +422,12 @@ public:
 
          std::size_t chunkEntry = 0;
          std::vector<std::pair<Long_t, Long_t>> BlocksInChunk = fValidation->ChunksIntervals[chunk];
+
+         std::sort(BlocksInChunk.begin(), BlocksInChunk.end(),
+                   [](const std::pair<Long_t, Long_t>& a, const std::pair<Long_t, Long_t>& b) {
+                      return a.first < b.first;
+                   });
+         
          for (std::size_t i = 0; i < BlocksInChunk.size(); i++) {
 
             // use the block start and end entry to load into the chunk if the dataframe is not filtered