QUANTICS: Program Usage

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Starting the Program

To start the program on a platform for which you have compiled it just type:

quantics [-opt] arguments

where arguments specifies any arguments required by the program.

To find the possible options and arguments required for a program, the argument -h can be used, e.g.

quantics -h

As the help text says, typically an argument specifying the input file is required. Assume your input file is named test.inp and your current directory is the directory on which test.inp resides, then you may just type:

quantics test


quantics test.inp

The executable name may change if options have been used durint compilation. For example, if you employed the options "-d" and "-n myver" in the compilation of the program (see Compiling the Program in Installation and Compilation), and your input file is not stored in your current directory but in the one specified by path, then you will have to type:

quanticsd_myver path/test

Note that the usual bash shortcuts are allowed to specify the path, e.g. the constructs ../test or ~/test are possible.

You may also run the input file through the C preprocessor (CPP) prior to interpretation. This way, you can share basis sets, initial states or any other settings between several input files by using a statement of the form

#include "somecommonsettings.inc"

This assures automatic consistency for the settings in the include file(s). To invoke CPP prior to interpretation by QUANTICS, type

quantics -cpp test.inp

The output of CPP is saved in a temporary file in the directory where the input file resides. Please make sure that this directory has write permission for QUANTICS. In addition to this, QUANTICS saves the settings as it understands them in the file input in the name directory. You can check this to see whether QUANTICS received the correct settings and CPP worked as desired.

Note that, when the -cpp option is used, it may be possible that CPP gets confused by comments starting with a hash character '#'. To be on the safe side, use C-style comments of the form

/* some comment */

Note that QUANTICS interprets '/*' like '#', i.e. everything which follows til the end of the line is a comment and is thus ignored. The end-of-comment sign */ is only needed for CPP. Thus a comment /*..*/ must not go over several lines, on has to bracket each line individually.

For an example see inputs/allene_b.inp and inputs/allene_common1.inc

On top of include files, you may of course use any other of the multiple powerful features of CPP, such as environment variable dependencies or macros. A full documentation of CPP can be found on this Free Software Foundation webpage.

As a final example, a continuation run may be started as:

quantics -c -I name -tfinal 250.0d0

The input is now taken from the file name/input rather than requiring a .inp file.

The use of options is often more convenient than changing the input file. For example, parameters are used to specify the input or the Hamiltonian. If different values are required for different calculations, one can either have different files specifying the different operators, or else different calculations can be started using the -p option, followed by a parameter name and a parameter value. E.g.:

quantics -p jtot 8 -p omega 0.35,eV test.inp

NB: Parameters are always real numbers.

Finally, the command

quantics -ver

prints information about the program version, included potential energy surfaces, and the date and time of the compilation. And the command

quantics -max

lists the set of the currently used maximal parameter values.

Propagation of density operators

For the propagation of density operators add the keyword




to the RUN-SECTION. All features can be used in the same manner as described above.

Input Parameters

The input file contains lines of input keywords and parameters. These are detailed in the Input documentation. Parameters may alternatively supplied a options. See above.

Output Data

Data files are created in a directory specified in the .inp file. Which data files are created depends on the keywords in the RUN-SECTION of the input file. See "Run-section" in the Input documentation.

The format of the various files is governed by the program version number, and are detailed in the Output documentation.

Hamiltonians/ Liouvillians

In order to apply a desired Hamiltonian/Liouvillian, it is necessary to have an appropriate operator file. In this file, the operator is defined using symbols to represent the various one- or multi-dimensional operators. For simple operators, these symbols are known to the program, and are called "internal terms". Other operators can be defined and read from other sources as "external terms". For details see Hamiltonian/Liouvillian documentation.

Stopping the Program

During a calculation the program can be stopped in a controlled way such that the calculation can be resumed later. This is done employing the stop file.

Running on Parallel Architectures

The Quantics code can be compiled to run on multiple processors using either the OpenMP or MPI protocols. The codes are called quantics.omp or quantics.mpi respectively. For details on compilation see Installation and Compilation .

For OpenMP the number of processors requested can be done either by adding the keyword openmp = N to the RUN-SECTION of the input file, or by using the run-time option quantics.omp -omp N input where N is the number of processors.

For MPI, the number of processors is requested using the mpi environment. In most linux installations, to ask for N processors, this requires: mpirun -np N quantics.mpi -mpi input One could also use the usempi keyword in the RUN-SECTION instead of the -mpi run-time option.

Parallelisation in the code is made over terms in the Hamiltonian. It is thus only efficient if the Hamiltonian has a long expansion.