very process can perform I/O using the standard facilities, this routine will return <code class="computeroutput">any_source</code>; if no process can perform I/O, this routine will return no value (an empty <code class="computeroutput">optional</code>). This routine examines the <code class="computeroutput">MPI_IO</code> attribute of <code class="computeroutput">MPI_COMM_WORLD</code>.</p>
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