GraphEnt is an attempt to provide an automatic way for calculating the maximum entropy map that corresponds to a set of observations, while offering a useful graphical output of the current stage of the calculations. Here is a typical screenshot from a SGI workstation running GraphEnt :
The automation is mainly directed towards the macromolecular crystallographic community, with direct support for CCP4 mtz reflection files. Doing the calculation is as simple as GraphEnt my_file.mtz (for a fully automated run), or GraphEnt h0l 10.0 3.5 my_file.mtz (for calculating the GraphEnt map corresponding to the [010] projection using only data between 10.0 and 3.5Å resolution).
Having said that, it is still quite easy for the general crystallographic community to use the program. All is needed is an ASCII file containing unit cell dimensions and a list of reflections expanded to P1 :
AUTO 30.40 42.10 81.40 90.00 90.00 90.00 20 -7 -5 1 559.200 8.700 138.578 0.4500 -7 -5 2 276.600 11.400 220.410 0.3500 -7 -5 3 532.700 8.900 169.320 0.4400 ............................................... 8 0 0 415.500 9.500 180.000 0.4000
Clearly, this black-box approach leads to loss of flexibility1. For this reason, GraphEnt also supports a more detailed form of input files, like this one2 :
CELL 30.40 42.10 81.40 90.00 90.00 90.00 SPACEGROUP 20 GRID 128 64 64 PERM 3 1 2 FOM VERBOSE GRACYCLES 5 GRASECTION 14 GRAGRAYSCALE LAMBDA 1.0 MAP_FORMAT ccp4 REFL -7 -5 1 559.200 8.700 138.578 0.4500 -7 -5 2 276.600 11.400 220.410 0.3500 ............................................... 7 5 3 532.700 8.900 349.320 0.4400 8 0 0 415.500 9.500 180.000 0.4000
This document is organised as follows : first a bit about installation, then a few things about supported modes of operation and the automated modes of execution, and then the real thing (keyword description). I am also including a copy of the 1995 (obsolete) version of this program because it includes a little bit of theory and a few examples.