title: Creating an MPI_Datatype for a structure containing pointers
body: <p>I have the following structure.</p>
  
  <pre><code>typedef struct
  {
   int *Ai;
   double *Ax;
   int nz;
  }column;
  </code></pre>
  
  <p>I want to transfer this structure using <code>MPI_Send</code> and <code>MPI_Receive</code>. How do I create an <code>MPI_Datatype</code> for this structure?</p>