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Hello </div>
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I'm not familiar with QE yet, so I'm not 100% sure about what might be the most efficient setting for my QE simulations. <span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">So far I submitted QE jobs based
on very rough estimation for cores and memory. But now, I wish to learn more about how can I submit my relax/vc-relax jobs with the most efficient setting. So, please understand if my questions are very basic ones. I couldn't find enough information about
those in QE manual. </span></div>
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1) How much memory (=core) I need to ask when I submit? </div>
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<div style="margin: 0px">Our machine use Slurm system, and allocate ~5GB memory per one core, and<span style="margin: 0px; background-color: rgb(255, 255, 255); display: inline !important"> 1 node has 36 cores.<span style="margin: 0px"> </span></span></div>
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In relaxation output file, I can see a line "Estimated total dynamical RAM > 38.86 GB" at the early part of the output file. <span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">This means I need at least
38.86 GB of total memory for this calculation, right? </span></div>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">If then, any surpass amount of memory would be wasted? For example, if I requested total 45GB of memory (=9 cores) for this simulation when I submit this
job, does the 6.14 GB of memory will be wasted because it will never used? </span></div>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">Is this usually useful to request the exact amount of memory (=core) as the amount of "<span style="font-family: Calibri, Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255); display: inline !important">Estimated
total dynamical RAM"</span>? Or give more enough memory (=core)? </span></div>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">2) Node / core allocation. </span></div>
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Our machine use Slurm system, and allocate ~5GB memory per one core, and<span style="margin: 0px; background-color: rgb(255, 255, 255); display: inline !important"> 1 node has 36 cores.<span style="margin: 0px"> </span></span></div>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">For the relaxation job which request </span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">"Estimated
total dynamical RAM > 38.86 GB", I can call 8 cores with 5GB memory per core. In this case, for QE, is it more faster or efficient to request all 8 cores from the same single node or fewest nodes as possible? Or it doesn't matter to request different
cores from all different nodes? </span><br>
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<span style="font-family: Calibri, Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255); display: inline !important">In other words, does QE calculation (relax or vc-relax) get speed benefit from using smallest node possible with given amount
of cores? Or it doesn't matter? </span><br>
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Thank you </div>
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Best, </div>
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