message: Tune a constant that shows some minor improvements on the sparse op benchmarks.
diff: @@ -1237,7 +1237,9 @@ inline BlockingCounter* SparseMatMul<TL, TR>::ShuffleMatrix(
  const DeviceBase::CpuWorkerThreads* thread_pool, MatrixR* buffer) {
  DCHECK_EQ(N % 2, 0);
  DCHECK_LE(kNumOperands * sizeof(float) / sizeof(TR), N);
  - int num_threads = std::min(thread_pool->num_threads, 16);
  + // Note(nikhilsarda): This heuristic is optimal in benchmarks as of
  + // Jan 21, 2020.
  + int num_threads = std::min(thread_pool->num_threads, 8);
  BlockingCounter* counter = new BlockingCounter(num_threads);
  DCHECK_EQ(N, buffer->dimension(1));
  auto shuffle_work = [&mat, slice_row_start, slice_num_rows, slice_col_start,
  