<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Dear S.K.S., dear all:</div><div><br></div>I maintain that if a linear-response calculation takes longer than an ordinary SCF calculation for a same system, this can only be due to the fact that the implementation of LRT is not as optimized as that of SCF. This may well be the case for codes in Quantum Espresso, at least for some systems, but it has NOT to be so by necessity. If it continues to be so it is that too many people have misconceptions about LRT and/or have not the time/fiber/keennes to improve upon existing implementations. Nothing wrong with this state of affairs, given the fact that SCF calculations have a much larger scope of application. It would be worse if SCF were less optimized than LRT. This being said, I believe that general and apodictic statements such as those made by SKS should be substantiated by more solid arguments than episodic experience. Once again, nothing wrong in reporting about one's own episodic experience, provided it is reported as such, and not as an absolute truth.<div><br></div><div>Cheers, Stefano</div><div><br><div><div>On Aug 9, 2008, at 8:30 AM, S. K. S. wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div dir="ltr"><br> <br><div class="Ih2E3d"><br></div> <div class="gmail_quote">On Sat, Aug 9, 2008 at 1:52 AM, Paolo Giannozzi <span dir="ltr"><<a href="mailto:giannozz@democritos.it">giannozz@democritos.it</a>></span> wrote:</div><div class="Ih2E3d">> Only for Gamma point phonon one can use "Frozen<br> > phonon" method because it is much faster.<br> <br> </div>not true in general. Each linear-response calculation<br> costs approx. as much as a self-consistent one, and<br> you need at least as many scf calculations as<br> linear-response calculations.<br><br>Dear Sir, <br>I agree with you that for small system each <br>linear-response calculation<br> costs approx. as much as a self-consistent one, and<br> we need at least as many scf calculations as<br> linear-response calculations.<br><br>However, IN CASE OF very large system (say about 64 atoms per unit cell), <br>I found that a single representation takes too much computer time <br>compared to a single scf run.<br> <br>Moreover, in some cluster which have multiple cpu <br>for each node and in some quad or octa core computer, always <br>phonon paralization is much slower than manual <br>scf paralization (I mean manually divide your all scf calculations in <br> different processors). In case of Frozen phonon method, one can <br>also accomplish the same goal by using less memory and <br>disk space.<br>However, for non-zone center phonon Linear response is the best way. <br>There is still a scope in PWSCF to make Phonon calculation much faster <br> by implementing the representation number parallization.<br><br>regards,<br>SKS<br>JNCASR<br>BANGALORE <br> <div class="Ih2E3d"><br><br></div><div class="gmail_quote">On Sat, Aug 9, 2008 at 1:52 AM, Paolo Giannozzi <span dir="ltr"><<a href="mailto:giannozz@democritos.it">giannozz@democritos.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <div class="Ih2E3d"><br> On Aug 8, 2008, at 18:41 , S. K. S. wrote:<br> <br> > Only for Gamma point phonon one can use "Frozen<br> > phonon" method because it is much faster.<br> <br> </div>not true in general. Each linear-response calculation<br> costs approx. as much as a self-consistent one, and<br> you need at least as many scf calculations as<br> linear-response calculations<br> <div class="Ih2E3d"><br> Paolo<br> ---<br> Paolo Giannozzi, Dept of Physics, University of Udine<br> via delle Scienze 208, 33100 Udine, Italy<br> Phone +39-0432-558216, fax +39-0432-558222<br> <br> <br> <br> </div></blockquote></div><br></div> _______________________________________________<br>Pw_forum mailing list<br><a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>http://www.democritos.it/mailman/listinfo/pw_forum<br></blockquote></div><br></div><br><br><div apple-content-edited="true"> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; 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color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">---</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">Stefano Baroni - SISSA</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">&</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">DEMOCRITOS National Simulation Center - Trieste</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><a href="http://www.sissa.it/~baroni">http://www.sissa.it/~baroni</a> / [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; font-size: 12px; "><br style="font-size: 12px; "></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; font-size: 12px; "><span class="Apple-style-span" style="font-size: 14px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "><br></span></font></div></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">Please, if possible, don't</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "> </span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">send me MS Word or PowerPoint attachments</span></font></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; ">Why? See:</span></font><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 12px; "> </span></font><font class="Apple-style-span" color="#0023E9" size="3"><span class="Apple-style-span" style="font-size: 12px; "><a href="http://www.gnu.org/philosophy/no-word-attachments.html">http://www.gnu.org/philosophy/no-word-attachments.html</a></span></font></div><div><font class="Apple-style-span" color="#0023E9" size="3"><span class="Apple-style-span" style="font-size: 12px; "><br class="webkit-block-placeholder"></span></font></div></div></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"></div></span><br class="Apple-interchange-newline"> </div><br></body></html>