mirror of
https://github.com/QuantumPackage/qp2.git
synced 2024-11-18 11:23:38 +01:00
112 lines
4.8 KiB
ReStructuredText
112 lines
4.8 KiB
ReStructuredText
=======================
|
|
Programming in the |qp|
|
|
=======================
|
|
|
|
To program in the |qp|, it is required that you are familiar with the |IRPF90|
|
|
code generator. A GitBook can be found `here <http://scemama.gitbooks.io/irpf90>`_,
|
|
and programmers are encouraged to visit this manual.
|
|
|
|
|IRPF90| makes programming very simple. The only information a programmer needs
|
|
in order to write a new program is the name of the required |IRPF90| entities
|
|
which may already exist in other modules. For example, writing a program which
|
|
prints the Hartree-Fock energy is as simple as:
|
|
|
|
.. code:: fortran
|
|
|
|
program print_hf_energy
|
|
implicit none
|
|
BEGIN_DOC
|
|
! Program which prints the Hartree-Fock energy
|
|
! to the standard output
|
|
END_DOC
|
|
print *, 'HF energy = ', HF_energy
|
|
end
|
|
|
|
|
|
The only required information was the existence of a provider for
|
|
:command:`HF_energy`. A detailed list of all the providers, subroutines
|
|
and functions of the |qp| can be found in the appendix of this manual.
|
|
|
|
|
|
|
|
Architecture
|
|
============
|
|
|
|
As |IRPF90| is used, the programmer doesn't have full control of the sequence
|
|
of instructions in the produced Fortran code. This explains why the input data
|
|
is stored in a database rather than in sequential text files. Consequently, the
|
|
programmer can't know in advance the order in which the files will be read, so a
|
|
simple random access to persistent data is needed. The |EZFIO| library generator
|
|
is a practical answer to this problem.
|
|
|
|
The |qp| uses a collection of programs inter-operating together. Each of these
|
|
programs is reading and/or modifying information in the |EZFIO| database.
|
|
This is done mostly using the command line or scripting.
|
|
|
|
.. important::
|
|
|
|
Each command modifies the state of the |EZFIO| database, so running the
|
|
same program twice on the same database may have different behavior because of the
|
|
state of the database. For reproducibility, users are encouraged to run scripts
|
|
where a fresh new |EZFIO| database is created at the beginning of the
|
|
script. This way of running the |qp| makes calculations reproducible.
|
|
|
|
|
|
The computational part |qp| is organized in **modules**. A module is a
|
|
directory which contains multiple |IRPF90| files, a |README| and a |NEED| file.
|
|
|
|
The |README| file contains documentation about the module, that is
|
|
automatically included in the documentation of the |qp|. The documentation is
|
|
generated by the `Sphinx documentation builder <http://www.sphinx-doc.org>`_,
|
|
and it should be written using the |rst| format.
|
|
|
|
The |NEED| file contains the list of the modules which are needed for the
|
|
current module. When a module is needed, it means that all the |IRPF90| files
|
|
it contains should be included in the current module. This is done
|
|
automatically during the building process, by creating symbolic links in the
|
|
current directory.
|
|
|
|
To compile the program, the |Ninja| build system is used, and all the building
|
|
process is fully automated such that the programmer will never have to modify a
|
|
file by hand. Running :command:`ninja` inside a module will compile only the
|
|
module, and running :command:`ninja` at the root of the |qp| will build all the
|
|
modules, as well as the tools.
|
|
|
|
|
|
Algorithms
|
|
==========
|
|
|
|
The `PhD thesis of Yann Garniron <https://doi.org/10.5281/zenodo.2558127>`_
|
|
gives all the details about the implementation of:
|
|
|
|
* The data structure for the two-electron integrals (:file:`utils/map_module.f`)
|
|
* The Davdison diagonalization (module :ref:`module_davidson`)
|
|
* The CIPSI selection (module :ref:`module_cipsi`)
|
|
* The hybrid stochastic/deterministic PT2 correction (module :ref:`module_cipsi`)
|
|
* The hybrid stochastic/deterministic matrix dressing (module :ref:`module_dressing`)
|
|
|
|
|
|
Extracting results for use with other codes
|
|
===========================================
|
|
|
|
The |AOs| and |MOs| can be seen with :ref:`qp_edit`. We also provide a utility
|
|
to create a file which can be read by `molden` for visualizing the |MOs| (see
|
|
:ref:`molden`). For using external |CI| solvers, we provide a utility that
|
|
generates a file containing the two-electron integrals in the |MO| basis set
|
|
in the `FCIDUMP` format (see :ref:`fcidump`).
|
|
|
|
All the results are stored in the |EZFIO| directory, so users willing to fetch
|
|
data such as the |MOs| or the |CI| coefficients should use the |EZFIO| API.
|
|
There are multiple major ways to do this:
|
|
|
|
* Write a script in Python or OCaml and use the Python |EZFIO| API. The script
|
|
:file:`$QP_ROOT/bin/qp_convert_output_to_ezfio` is a good example to understand
|
|
how to use the |EZFIO| API in Python,
|
|
* Write an independent program in Fortran or C, link it with the |EZFIO| library
|
|
located at :file:`$QP_ROOT/external/ezfio/lib/libezfio.a` and call directly
|
|
the |EZFIO| routines,
|
|
* Write a new module for the |qp| printing the desired quantities in a suitable
|
|
text format. The program :ref:`fcidump` is an example of such a program.
|
|
|
|
|