title: How to improve the speed of MPI_scatter/MPI_gather?
body: <p>I found that time used for MPI_scatter/MPI_gather continuously increased (somehow linearly) as the number of workers increases, especially when the workers are across different nodes.</p>
  
  <p>I thought that MPI_scatter/MPI_gather is a parallel process, and wonder what leads to the above increasing? Is there any trick to make it faster, especially for workers distributing across CPU nodes?</p>