[gmx-users] REMD

[merc mertens]

hello,

i am still trying to figure out how demultiplexing with trjcat (version 3.3.1) works.
i produced 3 trajectories, each containing only one frame:
e.g.

traj0.xtc frame 0:
   natoms=     14670  step=       500  time=         1  prec=      1000
   box (3x3):
      box[    0]={ 8.47401e+00,  0.00000e+00,  0.00000e+00}
      box[    1]={ 0.00000e+00,  4.98164e+00,  0.00000e+00}
      box[    2]={ 0.00000e+00,  0.00000e+00,  3.48938e+00}
   x (14670x3):
      x[    0]={ 1.95100e+00,  2.11100e+00,  3.09600e+00}
      x[    1]={ 1.95000e+00,  2.14800e+00,  3.19000e+00}
      x[    2]={ 1.88400e+00,  2.15100e+00,  3.03200e+00}
      x[    3]={ 1.94800e+00,  2.01100e+00,  3.11200e+00}
...

traj1.xtc and traj2.xtc look the same (apart from containing different coordinates).

remd.xvg for -demux contains only one line:

"1 2 1 0"

using those files with:
trjcat -f traj0.xtc traj1.xtc traj2.xtc -demux remd.xvg

produces: trajout.xtc

trajout.xtc frame 0:
   natoms=         0  step=       500  time=         1  prec=  -1.99104
   box (3x3):
      box[    0]={ 8.48018e+00,  0.00000e+00,  0.00000e+00}
      box[    1]={ 0.00000e+00,  4.98527e+00,  0.00000e+00}
      box[    2]={ 0.00000e+00,  0.00000e+00,  3.49192e+00}
not available: x

so, even if there are definitely coordinates in the trajectory and there can not be a mistake in the frame number, since there is only one, it seems strange to me, that trjcat does not output anything but the box to the *xtc file. further, the statement "not available: x" seems curious to me. 

thanks for any help,
merc







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