4 .. TODO in future patch: update for accuracy, organize better, improve formatting
6 Summary of file formats
7 ^^^^^^^^^^^^^^^^^^^^^^^
13 run parameters, input for :ref:`gmx grompp` and :ref:`gmx convert-tpr`
16 input for :ref:`gmx xpm2ps`
26 brookhaven Protein DataBank format
27 **Structure+mass(db):** :ref:`tpr`, :ref:`gro`, :ref:`g96`, or :ref:`pdb`
28 Structure and mass input for analysis tools.
29 When gro or pdb is used approximate masses will be read from the mass database.
35 system topology (ascii)
37 include topology (ascii)
39 residue topology (ascii)
47 system topology, parameters, coordinates and velocities (binary, portable)
53 Any kind of data (compressed, portable, any precision)
55 x, v and f (binary, full precision, portable)
57 x only (compressed, portable, any precision)
59 x and v (ascii, any precision)
61 x only (ascii, fixed high precision)
63 x only (ascii, reduced precision)
64 **Formats for full-precision data:**
65 :ref:`tng` or :ref:`trr`
66 **Generic trajectory formats:**
67 :ref:`tng`, :ref:`xtc`, :ref:`trr`, :ref:`gro`, :ref:`g96`, or :ref:`pdb`
73 energies, temperature, pressure, box size, density and virials (binary)
75 energies, temperature, pressure, box size, density and virials (binary, portable)
76 **Generic energy formats:**
77 :ref:`edr` or :ref:`ene`
83 generic, preferred for input
85 essential dynamics constraints input for :ref:`gmx mdrun`
87 essential dynamics constraints output for :ref:`gmx mdrun`
89 Encapsulated Postscript
93 colormap input for :ref:`gmx do_dssp`
97 generic, preferred for output
101 ascii matrix data, use :ref:`gmx xpm2ps` to convert to :ref:`eps`
113 The cpt file extension stands for portable checkpoint file.
114 The complete state of the simulation is stored in the checkpoint file,
115 including extended thermostat/barostat variables, random number states
116 and NMR time averaged data.
117 With domain decomposition also the some decomposition setup information
120 See also :ref:`gmx mdrun`.
127 Files with the dat file extension contain generic input or output.
128 As it is not possible
129 to categorise all data file formats, GROMACS has a generic file format called
130 dat of which no format is given.
137 The dlg file format is used as input for the :ref:`gmx view`
138 trajectory viewer. These files are not meant to be altered by the end user.
147 group "Bond Options" 1 1 16 9 {
148 radiobuttons { " Thin Bonds" " Fat Bonds" " Very Fat Bonds" " Spheres" }
149 "bonds" "Ok" " F" "help bonds"
152 group "Other Options" 18 1 20 13 {
153 checkbox " Show Hydrogens" "" "" "FALSE" "help opts"
154 checkbox " Draw plus for atoms" "" "" "TRUE" "help opts"
155 checkbox " Show Box" "" "" "TRUE" "help opts"
156 checkbox " Remove PBC" "" "" "FALSE" "help opts"
157 checkbox " Depth Cueing" "" "" "TRUE" "help opts"
158 edittext "Skip frames: " "" "" "0" "help opts"
162 defbutton "Ok" "Ok" "Ok" "Ok" "help bonds"
172 Files with the edi file extension contain information for :ref:`gmx mdrun`
173 to run Molecular Dynamics with Essential Dynamics constraints.
175 .. WEDSAM and ESSDYN seem to have vanished from WhatIf and the web
176 These files can be generated by the program <tt>WEDSAM</tt> which uses
177 output from the programs in the <tt>ESSDYN</tt> menu of the
178 <A HREF="http://www.sander.embl-heidelberg.de/whatif/">WHAT IF</A> program.
185 Files with the edo file extension are generated by :ref:`gmx mdrun`
186 if Molecular Dynamics is performed with Essential Dynamics
187 constraints. Depending on the parameters set in the :ref:`edi`:
188 file, edo files may contain projections of positions,
189 velocities and forces onto selected eigenvectors during the run as well
190 as RMSD values, or information about specific types of constraints.
191 Specific results can be extracted from the edo files with standard Unix
192 utilities like ``awk``.
199 The edr file extension stands for portable energy file.
200 The energies are stored using the xdr protocol.
202 See also :ref:`gmx energy`.
209 The ene file extension stands for binary energy file. It holds the
210 energies as generated during your :ref:`gmx mdrun`.
212 The file can be transformed to a portable energy file (portable
213 across hardware platforms), the :ref:`edr` file using the program
216 See also :ref:`gmx energy`.
223 The eps file format is not a special GROMACS format, but just a
224 variant of the standard PostScript(tm). A sample eps file as
225 generated by the :ref:`gmx xpm2ps` program is
226 included below. It shows the secondary structure of a peptide as a function
229 .. image:: plotje.gif
237 A file with the g96 extension can be a GROMOS-96 initial/final
238 configuration file or a coordinate trajectory file or a combination of both.
239 The file is fixed format, all floats are written as 15.9 (files can get huge).
240 GROMACS supports the following data blocks in the given order:
244 - ``TITLE`` (mandatory)
248 - ``TIMESTEP`` (optional)
249 - ``POSITION/POSITIONRED`` (mandatory)
250 - ``VELOCITY/VELOCITYRED`` (optional)
253 See the GROMOS-96 manual for a complete description of the blocks.
255 Note that all GROMACS programs can read compressed or g-zipped files.
262 Files with the gro file extension contain a molecular structure in
263 Gromos87 format. gro files can be used as trajectory by simply
264 concatenating files. An attempt will be made to read a time value from
265 the title string in each frame, which should be preceded by
266 '``t=``', as in the sample below.
268 A sample piece is included below::
270 MD of 2 waters, t= 0.0
272 1WATER OW1 1 0.126 1.624 1.679 0.1227 -0.0580 0.0434
273 1WATER HW2 2 0.190 1.661 1.747 0.8085 0.3191 -0.7791
274 1WATER HW3 3 0.177 1.568 1.613 -0.9045 -2.6469 1.3180
275 2WATER OW1 4 1.275 0.053 0.622 0.2519 0.3140 -0.1734
276 2WATER HW2 5 1.337 0.002 0.680 -1.0641 -1.1349 0.0257
277 2WATER HW3 6 1.326 0.120 0.568 1.9427 -0.8216 -0.0244
278 1.82060 1.82060 1.82060
280 Lines contain the following information (top to bottom):
282 * title string (free format string, optional time in ps after '``t=``')
283 * number of atoms (free format integer)
284 * one line for each atom (fixed format, see below)
285 * box vectors (free format, space separated reals), values:
286 v1(x) v2(y) v3(z) v1(y) v1(z) v2(x) v2(z) v3(x) v3(y),
287 the last 6 values may be omitted (they will be set to zero).
288 |Gromacs| only supports boxes with v1(y)=v1(z)=v2(z)=0.
290 This format is fixed, ie. all columns are in a fixed
291 position. Optionally (for now only yet with trjconv) you can write gro
292 files with any number of decimal places, the format will then be
293 ``n+5`` positions with ``n`` decimal places (``n+1``
294 for velocities) in stead of ``8`` with ``3`` (with
295 ``4`` for velocities). Upon reading, the precision will be
296 inferred from the distance between the decimal points (which will be
297 ``n+5``). Columns contain the following information (from left to
300 * residue number (5 positions, integer)
301 * residue name (5 characters)
302 * atom name (5 characters)
303 * atom number (5 positions, integer)
304 * position (in nm, x y z in 3 columns, each 8 positions with 3 decimal places)
305 * velocity (in nm/ps (or km/s), x y z in 3 columns, each 8 positions with 4 decimal places)
307 Note that separate molecules or ions (e.g. water or Cl-) are regarded
308 as residues. If you want to write such a file in your own program
309 without using the GROMACS libraries you can use the following formats:
312 ``"%5d%-5s%5s%5d%8.3f%8.3f%8.3f%8.4f%8.4f%8.4f"``
314 ``(i5,2a5,i5,3f8.3,3f8.4)``
316 This is left as an exercise for the user
318 Note that this is the format for writing, as in the above example
319 fields may be written without spaces, and therefore can not be read
320 with the same format statement in C.
327 The hdb file extension stands for hydrogen database
328 Such a file is needed by :ref:`gmx pdb2gmx`
329 when building hydrogen atoms that were either originally missing, or that
330 were removed with ``-ignh``.
337 The itp file extension stands for include topology. These files are included in
338 topology files (with the :ref:`top` extension).
345 Logfiles are generated by some GROMACS programs and are usually in
346 human-readable format. Use ``more logfile``.
353 The m2p file format contains input options for the
354 :ref:`gmx xpm2ps` program. All of these options
355 are very easy to comprehend when you look at the PosScript(tm) output
356 from :ref:`gmx xpm2ps`.
360 ; Command line options of xpm2ps override the parameters in this file
361 black&white = no ; Obsolete
362 titlefont = Times-Roman ; A PostScript Font
363 titlefontsize = 20 ; Font size (pt)
364 legend = yes ; Show the legend
365 legendfont = Times-Roman ; A PostScript Font
366 legendlabel = ; Used when there is none in the .xpm
367 legend2label = ; Used when merging two xpm's
368 legendfontsize = 14 ; Font size (pt)
369 xbox = 2.0 ; x-size of a matrix element
370 ybox = 2.0 ; y-size of a matrix element
371 matrixspacing = 20.0 ; Space between 2 matrices
372 xoffset = 0.0 ; Between matrix and bounding box
373 yoffset = 0.0 ; Between matrix and bounding box
374 x-major = 20 ; Major ticks on x axis every .. frames
375 x-minor = 5 ; Id. Minor ticks
376 x-firstmajor = 0 ; First frame for major tick
377 x-majorat0 = no ; Major tick at first frame
378 x-majorticklen = 8.0 ; x-majorticklength
379 x-minorticklen = 4.0 ; x-minorticklength
380 x-label = ; Used when there is none in the .xpm
381 x-fontsize = 16 ; Font size (pt)
382 x-font = Times-Roman ; A PostScript Font
383 x-tickfontsize = 10 ; Font size (pt)
384 x-tickfont = Helvetica ; A PostScript Font
395 y-tickfont = Helvetica
402 This file maps matrix data to RGB values which is used by the
403 :ref:`gmx do_dssp` program.
405 The format of this file is as follow: first line number of elements
406 in the colormap. Then for each line: The first character is
407 a code for the secondary structure type.
408 Then comes a string for use in the legend of the plot and then the
409 R (red) G (green) and B (blue) values.
411 In this case the colors are
412 (in order of appearance): white, red, black, cyan, yellow, blue, magenta, orange.
418 E B-Sheet 1.0 0.0 0.0
419 B B-Bridge 0.0 0.0 0.0
422 H A-Helix 0.0 0.0 1.0
423 G 3-Helix 1.0 0.0 1.0
424 I 5-Helix 1.0 0.6 0.0
431 See the user guide for a detailed description of the options.
433 Below is a sample mdp file.
434 The ordering of the items is not important, but if you enter the same
435 thing twice, the **last** is used (:ref:`gmx grompp` gives you a note when
436 overriding values). Dashes and underscores on the left hand side are ignored.
438 The values of the options are reasonable values for a 1 nanosecond
439 MD run of a protein in a box of water.
454 nstxout-compressed = 250
455 compressed-x-grps = Protein
456 energygrps = Protein SOL
460 coulombtype = cut-off
464 tc-grps = Protein SOL
469 compressibility = 4.5e-5
474 constraints = all-bonds
476 With this input :ref:`gmx grompp` will produce
477 an ``mdout.mdp`` with all the options and descriptions:
481 ; VARIOUS PREPROCESSING OPTIONS =
487 ; RUN CONTROL PARAMETERS =
489 ; start time and timestep in ps =
493 ; number of steps for center of mass motion removal =
497 ; LANGEVIN DYNAMICS OPTIONS =
498 ; Temperature, friction coefficient (amu/ps) and random seed =
503 ; ENERGY MINIMIZATION OPTIONS =
504 ; Force tolerance and initial step-size =
507 ; Max number of iterations in relax-shells =
509 ; Frequency of steepest descents steps when doing CG =
512 ; OUTPUT CONTROL OPTIONS =
513 ; Output frequency for coords (x), velocities (v) and forces (f) =
517 ; Output frequency for energies to log file and energy file =
520 ; Output frequency and precision for xtc file =
521 nstxout-compressed = 250
522 compressed-x-precision = 1000
523 ; This selects the subset of atoms for the xtc file. You can =
524 ; select multiple groups. By default all atoms will be written. =
525 compressed-x-grps = Protein
526 ; Selection of energy groups =
527 energygrps = Protein SOL
529 ; NEIGHBORSEARCHING PARAMETERS =
530 ; nblist update frequency =
532 ; ns algorithm (simple or grid) =
534 ; Periodic boundary conditions: xyz or none =
539 ; OPTIONS FOR ELECTROSTATICS AND VDW =
540 ; Method for doing electrostatics =
541 coulombtype = cut-off
544 ; Dielectric constant (DC) for cut-off or DC of reaction field =
546 ; Method for doing Van der Waals =
551 ; Apply long range dispersion corrections for Energy and Pressure =
553 ; Spacing for the PME/PPPM FFT grid =
554 fourierspacing = 0.12
555 ; FFT grid size, when a value is 0 fourierspacing will be used =
559 ; EWALD/PME/PPPM parameters =
564 ; OPTIONS FOR WEAK COUPLING ALGORITHMS =
565 ; Temperature coupling =
567 ; Groups to couple separately =
568 tc-grps = Protein SOL
569 ; Time constant (ps) and reference temperature (K) =
572 ; Pressure coupling =
574 Pcoupltype = Isotropic
575 ; Time constant (ps), compressibility (1/bar) and reference P (bar) =
577 compressibility = 4.5e-5
580 ; SIMULATED ANNEALING CONTROL =
582 ; Time at which temperature should be zero (ps) =
585 ; GENERATE VELOCITIES FOR STARTUP RUN =
590 ; OPTIONS FOR BONDS =
591 constraints = all-bonds
592 ; Type of constraint algorithm =
593 constraint-algorithm = Lincs
594 ; Do not constrain the start configuration =
595 unconstrained-start = no
596 ; Relative tolerance of shake =
598 ; Highest order in the expansion of the constraint coupling matrix =
600 ; Lincs will write a warning to the stderr if in one step a bond =
601 ; rotates over more degrees than =
603 ; Convert harmonic bonds to morse potentials =
606 ; NMR refinement stuff =
607 ; Distance restraints type: No, Simple or Ensemble =
609 ; Force weighting of pairs in one distance restraint: Equal or Conservative =
610 disre-weighting = Equal
611 ; Use sqrt of the time averaged times the instantaneous violation =
615 ; Output frequency for pair distances to energy file =
618 ; Free energy control stuff =
625 ; Non-equilibrium MD stuff =
634 ; Format is number of terms (int) and for all terms an amplitude (real) =
635 ; and a phase angle (real) =
643 ; User defined thingies =
660 Files with the mtx file extension contain a matrix.
661 The file format is identical to the :ref:`trr` format.
662 Currently this file format is only used for hessian matrices,
663 which are produced with :ref:`gmx mdrun` and read by
671 The GROMACS index file (usually called index.ndx) contains some
672 user definable sets of atoms. The file can be read by
673 most analysis programs, by the graphics program
675 and by the preprocessor (:ref:`gmx grompp`).
676 Most of these programs create default index groups when no index
677 file is supplied, so you only need to make an index file when you need special
680 First the group name is written between square brackets.
681 The following atom numbers may be spread out over as many lines as you like.
682 The atom numbering starts at 1.
684 An example file is here:
694 There are two groups, and total nine atoms. The first group
695 **Oxygen** has 3 elements.
696 The second group **Hydrogen** has 6 elements.
698 An index file generation tool is available:
706 Files with the out file extension contain generic output. As it is not possible
707 to categorise all data file formats, GROMACS has a generic file format called
708 out of which no format is given.
716 Files with the :ref:`pdb` extension are molecular
717 structure files in the protein databank file format. The protein
718 databank file format describes the positions of atoms in a molecular
719 structure. Coordinates are read from the ATOM and HETATM records,
720 until the file ends or an ENDMDL record is encountered.
721 GROMACS programs can read and write a simulation box in the
723 The pdb format can also be used as a trajectory format:
724 several structures, separated by ENDMDL, can be read from
725 or written to one file.
730 A pdb file should look like this::
732 ATOM 1 H1 LYS 1 14.260 6.590 34.480 1.00 0.00
733 ATOM 2 H2 LYS 1 13.760 5.000 34.340 1.00 0.00
734 ATOM 3 N LYS 1 14.090 5.850 33.800 1.00 0.00
735 ATOM 4 H3 LYS 1 14.920 5.560 33.270 1.00 0.00
744 The rtp file extension stands for residue topology.
745 Such a file is needed by :ref:`gmx pdb2gmx`
746 to make a GROMACS topology for a protein contained in a :ref:`pdb`
747 file. The file contains the default interaction type for the 4 bonded
748 interactions and residue entries, which consist of atoms and
749 optionally bonds, angles dihedrals and impropers.
750 Parameters can be added to bonds, angles, dihedrals and impropers,
751 these parameters override the standard parameters in the :ref:`itp` files.
752 This should only be used in special cases.
753 Instead of parameters a string can be added for each bonded interaction,
754 the string is copied to the :ref:`top` file,
755 this is used for the GROMOS96 forcefield.
757 :ref:`gmx pdb2gmx` automatically generates all angles,
758 this means that the ``[angles]`` field is only
759 useful for overriding :ref:`itp` parameters.
761 :ref:`gmx pdb2gmx` automatically generates one proper
762 dihedral for every rotatable bond, preferably on heavy atoms.
763 When the ``[dihedrals]`` field is used, no other dihedrals will
764 be generated for the bonds corresponding to the specified dihedrals.
765 It is possible to put more than one dihedral on a rotatable bond.
767 :ref:`gmx pdb2gmx` sets the number exclusions to 3, which
768 means that interactions between atoms connected by at most 3 bonds are
769 excluded. Pair interactions are generated for all pairs of atoms which are
770 separated by 3 bonds (except pairs of hydrogens).
771 When more interactions need to be excluded, or some pair interactions should
772 not be generated, an ``[exclusions]`` field can be added, followed by
773 pairs of atom names on separate lines. All non-bonded and pair interactions
774 between these atoms will be excluded.
776 A sample is included below.
780 [ bondedtypes ] ; mandatory
781 ; bonds angles dihedrals impropers
786 [ atoms ] ; mandatory
787 ; name type charge chargegroup
802 [ exclusions ] ; optional
805 [ angles ] ; optional
806 ;atom1 atom2 atom3 th0 cth
808 [ dihedrals ] ; optional
809 ;atom1 atom2 atom3 atom4 phi0 cp mult
811 [ impropers ] ; optional
812 ;atom1 atom2 atom3 atom4 q0 cq
826 We use **LaTeX** for *document* processing.
827 Although the input is not so
828 user friendly, it has some advantages over *word* processors.
830 * **LaTeX** knows a lot about formatting, probably much more than you.
831 * The input is clear, you always know what you are doing
832 * It makes anything from letters to a thesis
840 Files with the ``.tng`` file extension can contain all kinds of data
841 related to the trajectory of a simulation. For example, it might
842 contain coordinates, velocities, forces and/or energies. Various :ref:`mdp`
843 file options control which of these are written by mdrun, whether data
844 is written with compression, and how lossy that compression can be.
845 This file is in portable binary format an can be read with :ref:`gmx dump`.
849 % :ref:`gmx dump` -f traj.tng
851 or if you're not such a fast reader::
853 % gmx dump -f traj.tng | less
855 You can also get a quick look in the contents of the file (number of
860 % :ref:`gmx check` -f traj.tng
867 The top file extension stands for topology. It is an ascii file which is
868 read by :ref:`gmx grompp` which processes it
869 and creates a binary topology (:ref:`tpr` file).
871 A sample file is included below::
874 ; Example topology file
877 ; nbfunc comb-rule gen-pairs fudgeLJ fudgeQQ
880 ; The force field files to be included
881 #include "rt41c5.itp"
888 ; nr type resnr residu atom cgnr charge
889 1 C 1 UREA C1 1 0.683
890 2 O 1 UREA O2 1 -0.683
891 3 NT 1 UREA N3 2 -0.622
892 4 H 1 UREA H4 2 0.346
893 5 H 1 UREA H5 2 0.276
894 6 NT 1 UREA N6 3 -0.622
895 7 H 1 UREA H7 3 0.346
896 8 H 1 UREA H8 3 0.276
900 3 4 1 1.000000e-01 3.744680e+05
901 3 5 1 1.000000e-01 3.744680e+05
902 6 7 1 1.000000e-01 3.744680e+05
903 6 8 1 1.000000e-01 3.744680e+05
904 1 2 1 1.230000e-01 5.020800e+05
905 1 3 1 1.330000e-01 3.765600e+05
906 1 6 1 1.330000e-01 3.765600e+05
910 2 4 1 0.000000e+00 0.000000e+00
911 2 5 1 0.000000e+00 0.000000e+00
912 2 7 1 0.000000e+00 0.000000e+00
913 2 8 1 0.000000e+00 0.000000e+00
914 3 7 1 0.000000e+00 0.000000e+00
915 3 8 1 0.000000e+00 0.000000e+00
916 4 6 1 0.000000e+00 0.000000e+00
917 5 6 1 0.000000e+00 0.000000e+00
920 ; ai aj ak funct c0 c1
921 1 3 4 1 1.200000e+02 2.928800e+02
922 1 3 5 1 1.200000e+02 2.928800e+02
923 4 3 5 1 1.200000e+02 3.347200e+02
924 1 6 7 1 1.200000e+02 2.928800e+02
925 1 6 8 1 1.200000e+02 2.928800e+02
926 7 6 8 1 1.200000e+02 3.347200e+02
927 2 1 3 1 1.215000e+02 5.020800e+02
928 2 1 6 1 1.215000e+02 5.020800e+02
929 3 1 6 1 1.170000e+02 5.020800e+02
932 ; ai aj ak al funct c0 c1 c2
933 2 1 3 4 1 1.800000e+02 3.347200e+01 2.000000e+00
934 6 1 3 4 1 1.800000e+02 3.347200e+01 2.000000e+00
935 2 1 3 5 1 1.800000e+02 3.347200e+01 2.000000e+00
936 6 1 3 5 1 1.800000e+02 3.347200e+01 2.000000e+00
937 2 1 6 7 1 1.800000e+02 3.347200e+01 2.000000e+00
938 3 1 6 7 1 1.800000e+02 3.347200e+01 2.000000e+00
939 2 1 6 8 1 1.800000e+02 3.347200e+01 2.000000e+00
940 3 1 6 8 1 1.800000e+02 3.347200e+01 2.000000e+00
943 ; ai aj ak al funct c0 c1
944 3 4 5 1 2 0.000000e+00 1.673600e+02
945 6 7 8 1 2 0.000000e+00 1.673600e+02
946 1 3 6 2 2 0.000000e+00 1.673600e+02
948 ; Include SPC water topology
963 The tpr file extension stands for portable binary run input file. This file
964 contains the starting structure of your simulation, the molecular topology
965 and all the simulation parameters. Because this file is in binary format it
966 cannot be read with a normal editor. To read a portable binary run input
971 % :ref:`gmx dump` -s topol.tpr
973 or if you're not such a fast reader::
975 % gmx dump -s topol.tpr | less
977 You can also compare two tpr files using:
981 % :ref:`gmx check` -s1 top1 -s2 top2 | less
988 Files with the trr file extension contain the trajectory of a simulation.
989 In this file all the coordinates, velocities, forces and energies are
990 printed as you told GROMACS in your mdp file. This file is in portable binary
991 format an can be read with :ref:`gmx dump`::
993 % gmx dump -f traj.trr
995 or if you're not such a fast reader::
997 % gmx dump -f traj.trr | less
999 You can also get a quick look in the contents of the file (number of
1004 % :ref:`gmx check` -f traj.trr
1011 The GROMACS xpm file format is compatible with the XPixMap format
1012 and is used for storing matrix data.
1013 Thus GROMACS xpm files can be viewed directly with programs like XV.
1014 Alternatively, they can be imported into GIMP and scaled to 300 DPI,
1015 using strong antialiasing for font and graphics.
1016 The first matrix data line in an xpm file corresponds to the last matrix
1018 In addition to the XPixMap format, GROMACS xpm files may contain
1019 extra fields. The information in these fields is used when converting
1020 an xpm file to EPS with :ref:`gmx xpm2ps`.
1021 The optional extra field are:
1023 * Before the ``gv_xpm`` declaration: ``title``, ``legend``,
1024 ``x-label``, ``y-label`` and ``type``, all followed by a string.
1025 The ``legend`` field determines the legend title.
1026 The ``type`` field must be followed by ``"continuous"`` or
1027 ``"discrete"``, this determines which type of legend will be drawn in an EPS
1028 file, the default type is continuous.
1029 * The xpm colormap entries may be followed by a string, which is a label for
1031 * Between the colormap and the matrix data, the fields ``x-axis`` and/or
1032 ``y-axis`` may be present followed by the tick-marks for that axis.
1034 The example GROMACS xpm file below contains all the extra fields.
1035 The C-comment delimiters and the colon in the extra fields are optional.
1040 /* This matrix is generated by g_rms. */
1041 /* title: "Backbone RMSD matrix" */
1042 /* legend: "RMSD (nm)" */
1043 /* x-label: "Time (ps)" */
1044 /* y-label: "Time (ps)" */
1045 /* type: "Continuous" */
1046 static char * gv_xpm[] = {
1048 "A c #FFFFFF " /* "0" */,
1049 "B c #CCCCCC " /* "0.0399" */,
1050 "C c #999999 " /* "0.0798" */,
1051 "D c #666666 " /* "0.12" */,
1052 "E c #333333 " /* "0.16" */,
1053 "F c #000000 " /* "0.2" */,
1054 /* x-axis: 0 40 80 120 160 200 240 280 320 360 400 440 480 */
1055 /* y-axis: 0 40 80 120 160 200 240 280 320 360 400 440 480 */
1075 The xtc format is a **portable** format for trajectories.
1076 It uses the *xdr* routines for writing and reading
1077 data which was created for the Unix NFS system. The trajectories
1078 are written using a reduced precision algorithm which works
1079 in the following way: the coordinates (in nm) are multiplied by a scale
1080 factor, typically 1000, so that you have coordinates in pm.
1081 These are rounded to integer values. Then several other tricks are
1082 performed, for instance making use of the fact that atoms close
1083 in sequence are usually close in space too (e.g. a water molecule).
1084 To this end, the <i>xdr</i> library is extended with a special routine
1085 to write 3-D float coordinates.
1087 .. link is broken: This routine was written by Frans van Hoesel
1088 as part of an Europort project, and can be obtained through <a
1089 href="http://hpcv100.rc.rug.nl/xdrf.html">this link</a>.
1091 All the data is stored using calls to *xdr* routines.
1094 A magic number, for the current file version its value is 1995.
1096 The number of atoms in the trajectory.
1098 The simulation step.
1100 The simulation time.
1102 The computational box which is stored as a set of three basis
1103 vectors, to allow for triclinic PBC. For a rectangular box the
1104 box edges are stored on the diagonal of the matrix.
1105 **3dfcoord** x[natoms]
1106 The coordinates themselves stored in reduced precision.
1107 Please note that when the number of atoms is smaller than 9
1108 no reduced precision is used.
1110 Using xtc in your "C" programs
1111 ++++++++++++++++++++++++++++++
1113 To read and write these files the following "C" routines are available::
1115 /* All functions return 1 if successful, 0 otherwise */
1117 extern int open_xtc(XDR *xd,char *filename,char *mode);
1118 /* Open a file for xdr I/O */
1120 extern void close_xtc(XDR *xd);
1121 /* Close the file for xdr I/O */
1123 extern int read_first_xtc(XDR *xd,char *filename,
1124 int *natoms,int *step,real *time,
1125 matrix box,rvec **x,real *prec);
1126 /* Open xtc file, read xtc file first time, allocate memory for x */
1128 extern int read_next_xtc(XDR *xd,
1129 int *natoms,int *step,real *time,
1130 matrix box,rvec *x,real *prec);
1131 /* Read subsequent frames */
1133 extern int write_xtc(XDR *xd,
1134 int natoms,int step,real time,
1135 matrix box,rvec *x,real prec);
1136 /* Write a frame to xtc file */
1138 To use the library function include ``"gromacs/fileio/xtcio.h"``
1139 in your file and link with ``-lgmx.$(CPU)``.
1141 Using xtc in your FORTRAN programs
1142 ++++++++++++++++++++++++++++++++++
1144 To read and write these in a FORTRAN program use the calls to
1145 ``readxtc`` and ``writextc`` as in the following sample program
1146 which reads and xtc file and copies it to a new one::
1150 parameter (maxatom=10000,maxx=3*maxatom)
1151 integer xd,xd2,natoms,step,ret,i
1152 real time,box(9),x(maxx)
1154 call xdrfopen(xd,"test.xtc","r",ret)
1155 print *,'opened test.xtc, ret=',ret
1156 call xdrfopen(xd2,"testout.xtc","w",ret)
1157 print *,'opened testout.xtc, ret=',ret
1159 call readxtc(xd,natoms,step,time,box,x,prec,ret)
1161 if ( ret .eq. 1 ) then
1162 call writextc(xd2,natoms,step,time,box,x,prec,ret)
1164 print *,'Error reading xtc'
1170 To link your program use ``-L$(GMXHOME)/lib/$(CPU) -lxtcf``
1171 on your linker command line.
1178 Almost all output from GROMACS analysis tools is ready as input for
1179 Grace, formerly known as Xmgr. We use Grace, because it is very flexible, and it is also
1180 free software. It produces PostScript(tm) output, which is very suitable
1181 for inclusion in eg. LaTeX documents, but also for other word processors.
1183 A sample Grace session with GROMACS data is shown below: