<br><br>----- Original Message -----<br>From: Inon Sharony <InonShar@TAU.ac.IL><br>Date: Tuesday, August 3, 2010 20:55<br>Subject: [gmx-users] Precision in trajectory file<br>To: "gmx-users@gromacs.org" <gmx-users@gromacs.org>, gmx-developers <gmx-developers@gromacs.org><br><br>> Good afternoon!<br>> <br>> It seems to me that although I'm running a double-precision <br>> installation of GROMACS, the printout to file (of the positions <br>> and velocities) is of much less precision. i.e. the computation <br>> is done on numbers with something like 16 significant digits, <br>> but the last 10 of those are simply truncated and lost (e.g. <br>> positions are given in single-precision as 0.000 nm, and in <br>> double-precision as 0.00000 nm). Since I've already spent <br>> computation time at getting double-precision, I'd like to make <br>> use of all of it -- for my own reasons. I already searched the <br>> manuals, mailing lists and source code for instruction but <br>> didn't find any.<br>> Could you please tell me how I can change the number of digits <br>> printed out (e.g. to the .trr file)? I'm looking for a more <br>> elegant solution than adding a printf line to the source code. <br>> Something along the lines of changing the format of numbers in <br>> the function that prints to .trr .<br><br>You seem confused about something. The .trr file contains a binary representation of the value, in the appropriate precision. There's no nonsense about the number of digits *it* has - it has full single/double-precision binary floating-point numbers, and its precision is not measured in digits.<br><br>Some program that reads those numbers and writes human-readable forms might choose to lose precision, but the underlying precision was always there...<br><br>There's no straightforward way to get large amounts of precision output with GROMACS tools, because only a few of the digits are actually significant. You could hack the code to g_traj or gmxdump to get all the precision if you really want it.<br><br>Mark<br><br>> <br>> Thanks in advance!<br>> <br>> -- <br>> Inon Sharony<br>> ינון שרוני<br>> 972-3-6407634<br>> Please consider your environmental responsibility before <br>> printing this e-mail.<br>> <br>> -- <br>> gmx-users mailing list gmx-users@gromacs.org<br>> http://lists.gromacs.org/mailman/listinfo/gmx-users<br>> Please search the archive at http://www.gromacs.org/search <br>> before posting!<br>> Please don't post (un)subscribe requests to the list. Use the <br>> www interface or send it to gmx-users-request@gromacs.org.<br>> Can't post? Read http://www.gromacs.org/mailing_lists/users.php