[GitHub] [arrow] mapleFU commented on pull request #35422: MINOR: [C++] Use [] instead of exception-throwing at(i) in concatenate.cc

["mapleFU (via GitHub)" <gi...@apache.org>]

mapleFU commented on PR #35422:
URL: https://github.com/apache/arrow/pull/35422#issuecomment-1540558340

   ```c++
   
   static void VectorIndex(benchmark::State& state) {
     // Code inside this loop is measured repeatedly
     std::vector<int64_t> range_vec(10000, 0);
     for (auto _ : state) {
       // Make sure the variable is not optimized away by compiler
       for (int i = 0; i < 10000; ++i) {
         int64_t v = range_vec[i];
         benchmark::DoNotOptimize(v);
       }
     }
   }
   
   // Register the function as a benchmark
   BENCHMARK(VectorIndex);
   
   static void VectorAt(benchmark::State& state) {
     // Code inside this loop is measured repeatedly
     std::vector<int64_t> range_vec(10000, 0);
     for (auto _ : state) {
       // Make sure the variable is not optimized away by compiler
       for (int i = 0; i < 10000; ++i) {
         int64_t v = range_vec.at(i);
         benchmark::DoNotOptimize(v);
       }
     }
   }
   
   BENCHMARK(VectorAt);
   ```
   
   With release(-O2) on my MacOS:
   
   ```
   ------------------------------------------------------
   Benchmark            Time             CPU   Iterations
   ------------------------------------------------------
   VectorIndex      24632 ns        17785 ns        38620
   VectorAt         37438 ns        31141 ns        21829
   ```


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