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<div><span style="font-size: small; text-align: left; font-family: 'Times New Roman'; ">Hi all,</span></div>
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<div><span style="font-size: small; text-align: left; font-family: 'Times New Roman'; ">please see the following codes first,</span></div>
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<div><span style="font-size: small; text-align: left; font-family: 'Times New Roman'; "> mpi_start[]</span><span style="font-size: small; text-align: left; font-family: 'Times New Roman'; "> = ..</span><span style="font-size: small; text-align: left; font-family: 'Times New Roman'; ">;</span></div>
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<font size="2"><span style="font-family: 'Times New Roman'; "> </span><span style="font-family: 'Times New Roman'; ">mpi_count[]</span><span style="font-family: 'Times New Roman'; "> = ..</span><span style="font-family: 'Times New Roman'; ">;</span></font></p>
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<span style="font-size: small; font-family: 'Times New Roman'; "> ncmpi_get_vara_float_all();</span></p>
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<span style="font-size: small; font-family: 'Times New Roman'; "><br>
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<font face="'Times New Roman'" size="2">I can see the collective i/o is performed in the *_all function, which means all processes will call this function to do the i/o.</font></p>
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<font face="'Times New Roman'" size="2">What if I write the code in the following way,</font></p>
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loop_start=(int)(NREC/nprocs)*rank;</p>
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loop_length=(int)(NREC/nprocs);</p>
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/*parallel access datasets*/</p>
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for(rec = loop_start;rec <loop_start+loop_length; rec++)</p>
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{</p>
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for(lon = 0; lon < NLON; lon++){</p>
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mpi_start[0] = rec;</p>
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mpi_start[2] = lon;</p>
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ret = ncmpi_get_vara_float_all()</p>
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...</p>
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In the above codes, the outer loop is decomposed, then how the collective i/o will take effect in this case, if I specify mpirun -np 10 here.</p>
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In other word, can all the 10 processes cooperate with each other to do collective I/O anymore in this example?</p>
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If there is something wrong in my understanding, please point it out, thanks in advance.</p>
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Jialin</p>
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