<br><font size=2 face="sans-serif">Hi,</font>
<br>
<br><font size=2 face="sans-serif">I also have a question about the cubic
spline formula used for potentials and forces:</font>
<br>
<br><font size=2 face="sans-serif">As I understand it the spline formula
employed by GROMACS enforces that</font>
<br><font size=2 face="sans-serif">potentials and their second derivates
are continuous at the tables sites,</font>
<br><font size=2 face="sans-serif">but the first derivates, hence the forces
computed from the tables, are not.</font>
<br><font size=2 face="sans-serif">There is always a small discontinuity
at the table sites for the first derivatives and therefore the forces.</font>
<br><font size=2 face="sans-serif">I stumbled a across this when I used
Eric's kernel tester for BlueGene optimizations.</font>
<br>
<br><font size=2 face="sans-serif">I guess my question is: Do you really
want a spline formula that makes the forces discontinous ?</font>
<br><font size=2 face="sans-serif">Wouldn't it actually make more sense
to use a spline formulat that forces the potential and</font>
<br><font size=2 face="sans-serif">its first derivate to be continuous
? What's the rationale behind making the second derivate</font>
<br><font size=2 face="sans-serif">continuous anyway ?</font>
<br><font size=2 face="sans-serif"><br>
Viele Grüsse / Best regards,<br>
Dr. Mathias Pütz<br>
<br>
IT Specialist for Application Perfomance<br>
<br>
Deep Computing - Strategic Growth BusinessDeep <br>
IBM Systems & Technology Group<br>
<br>
e-mail: mpuetz@de.ibm.com<br>
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</font>