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    Hi Pratik,<br>
    <br>
    May I ask what kind of connection do you have between the two nodes
    when you run in parallel? Is it Gigabit Ethernet or something else?<br>
    <br>
    I would like to do the same thing but now have to pause as your
    experience.<br>
    <br>
    Thanks,<br>
    Rolly <br>
    <br>
    <div class="moz-cite-prefix">On 05/25/2016 06:50 PM, PRATIK DAS
      wrote:<br>
    </div>
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cite="mid:CAEyNvDvPjbLAfBwjs35bF_Ms7F4ZKyEKU6h5A36yRSqaKH3KwQ@mail.gmail.com"
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                          <div>Dear QE users,<br>
                          </div>
                          I am not a new user of quantum espresso.
                          Previously I worked on a single machine of 4
                          core. I simply worked with mpi by 'mpirun -np
                          4', and the job was faster than a serial run.<br>
                        </div>
                        Now I have a 2 node cluster. Each node consists
                        of 2 processors of 12 core each. Hence I made a
                        hostfile(for a single node) by specifying <br>
                        "node1 slots=24".<br>
                        Now my command is <br>
                      </div>
                      "mpirun --hostfile my_hostfile -np 24 ph.x <<a
                        moz-do-not-send="true" href="http://input.in"
                        target="_blank">input.in</a>> output.out".
                      This run takes 9hours and 39 minutes.<br>
                    </div>
                    But when I want to use both nodes by<br>
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                  "node1 slots=24<br>
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                node2 slots=24"<br>
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              & command<br>
              "mpirun --hostfile my_hostfile -np 48 ph.x <<a
                moz-do-not-send="true" href="http://input.in"
                target="_blank">input.in</a>> output.out -ni 6 -nk
              2",<br>
            </div>
             It is taking too much time to complete the job. Even it is
            now almost 26 hours over. 2nd q point calculation is going
            on.<br>
            <br>
          </div>
          NB: The job has only 4 q points.<br>
          <br>
        </div>
        I have also seen this in pw.x run. In a single node, it is
        taking only 2mins.<br>
        Command: mpirun --hostfile my_hostfile -np 24 pw.x <<a
          moz-do-not-send="true" href="http://input.in" target="_blank">input.in</a>>
        output.out.<br>
        <br>
        But in case of both nodes, it is taking almost half an hour.<br>
        <div>Command: mpirun --hostfile my_hostfile -np 48 pw.x <<a
            moz-do-not-send="true" href="http://input.in"
            target="_blank">input.in</a>> output.out<br>
          <br>
        </div>
        <div>Can anyone suggest me that why the jobs running on 2 nodes
          are slower than the jobs in single node?<br>
          <br>
        </div>
        <div>Thanks in advance.<br>
          <br>
          <br>
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        <div>Regards<br>
        </div>
        Pratik Kumar Das
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                            <div><i><span style="color:rgb(0,0,255)"><b>Pratik
                                    Kr. Das</b></span></i><br>
                            </div>
                            <span
                              style="background-color:rgb(224,102,102)"><span
                                style="color:rgb(106,168,79)"><span
                                  style="background-color:rgb(224,102,102)"><span><span
style="background-color:rgb(204,204,204)"></span></span></span><span
                                  style="color:rgb(11,83,148)"><span
                                    style="background-color:rgb(255,255,255)">Research
                                    Fellow<br>
                                  </span></span></span></span></div>
                          <div><span style="color:rgb(11,83,148)"><span
style="background-color:rgb(255,255,255)">High Pressure and Temperature
                                Lab<br>
                              </span></span></div>
                          <span style="color:rgb(11,83,148)"><span
                              style="background-color:rgb(255,255,255)">Faculty
                              of Science<br>
                            </span></span></div>
                        <span style="color:rgb(11,83,148)"><span
                            style="background-color:rgb(255,255,255)">Jadavpur
                            University<br>
                          </span></span></div>
                      <span style="color:rgb(11,83,148)"><span
                          style="background-color:rgb(255,255,255)">Kolkata
                          700032<br>
                        </span></span></div>
                    <div><span style="background-color:rgb(224,102,102)"><span
                          style="color:rgb(106,168,79)"><span
                            style="background-color:rgb(255,255,255)"><span
                              style="color:rgb(11,83,148)"></span><span></span></span></span></span><br>
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    <br>
    <pre class="moz-signature" cols="72">-- 
PhD. Research Fellow,
Dept. of Physics & Materials Science,
City University of Hong Kong
Tel: +852 3442 4000
Fax: +852 3442 0538</pre>
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