The @exe code is able to compute the following functions on a regular three-dimensional
grid:
@itemize
@item The electron pair localization function (EPLF)
@item The electron localization function (ELF)
@item The electron density
@end itemize
The gradients, the norm of the gradient and the laplacian of any of these
three functions can also be requested. Note that the ELF can only be calculated
for a single Slater determinant.

@section Using the provided interface
The @file{eplf_edit.py} script allows to modify easily the conditions of the calculation:
the choice of the functions to compute, the dimension of the grid, etc.
Running the following command
@example
eplf_edit.py test.out.ezfio
@end example
opens an input file in your default editor (defined by the @code{$EDITOR}
environment variable). Lines starting with a @code{#} character are commented.
The input file is separated in three sections.

@subsection The Computation section
If you are in a parallel environment, the first line of this section is
@example
nproc = 0
@end example
which defines the number of processors to use. If @code{nproc} is chosen equal to 0,
then the batch queuing system may choose itself the proper number of processors.
Otherwise, specify the number of processors you want to use.

Then, all the computable functions appear, preceded by empty parentheses. Put an
@code{X} between the parentheses for the functions you want to compute, for example
@example
(X) elf
( ) density
(X) eplf
@end example

@subsection The Edit section

You can edit the nuclear coordinates and/or the parameters of the grid by
un-commenting the @code{edit(geometry)} or @code{edit(grid_parameters)}
statements.

When you save and quit the current input file, a new file will be open containing
the parameters to edit. In the case of the grid parameters, as there is some redundance
between the possible inputs quantities, the @code{Default} keyword can be used to
replace the (x,y,z) specification.
@example
###########################
# Grid : test.out.ezfio
###########################

# Number of points along x, y, z
40 40 40

# Coordinates of the origin (x,y,z)
-3.000000 -4.744648 -5.322027

# Coordinates of the opposite point (x,y,z)
Default

# Step sizes (x,y,z)
Default
@end example

@subsection The Clear section
All the previously calculated grids are saved in the @ezfio database.
If the grid parameters are changed, these grids are inconsistent.
Therefore, it may be necessary to clear the previously calculated grids.
This can be realized by un-commenting the @code{clear(*)} statements.
The @code{clear(all)} statement clears all the grids, and also the grid
parameters.

@subsection Saving the input data
When the editor is closed, after saving the file, all the input data is
saved into the EZFIO database. It can be modified later by running again
the @file{eplf_edit.py} script. A shell script @file{run_test.out.ezfio.sh}
is automatically created to launch the calculation.