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dft_tools/doc/reference/c++/gf/gf_block.rst
Olivier Parcollet bdac3e159c work on doc for gf, and details.
- little details : code cleaning, clang formatting,  along
with documentation writing for c++ gf.
- separated the mesh in small class for better doc.
- work on documentation : reorganize specialisation, ...
2013-12-30 22:32:16 +01:00

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ReStructuredText

.. highlight:: c
.. _gf_block:
Block Green functions
=======================
This is a specialisation of :ref:`gf_and_view` for block functions.
A block Green function is nothing but Green function on a discrete domain representing the
block indices, and whose value is itself a Green function.
For convenience, the following aliases are provided ::
template<typename ... T> using block_gf = gf <block_index, gf<T...>>;
template<typename ... T> using block_gf_view = gf_view <block_index, gf<T...>>;
template<typename ... T> using block_gf_const_view = gf_const_view<block_index, gf<T...>>;
Constructors
--------------
The constructors of the gf.
target_shape_t = {}
Factories
-------------
Also several factories are provided for these block Green functions.
Factories for the regular type
.....................................
The factories for the regular type *gf* are ::
// From a number and a gf to be copied
template <typename Variable, typename Target, typename Opt>
block_gf<Variable, Target, Opt>
make_block_gf(int n, gf<Variable, Target, Opt> const & g);
// From a vector of gf (moving directly)
template <typename Variable, typename Target, typename Opt>
block_gf<Variable, Target, Opt>
make_block_gf(std::vector<gf<Variable, Target, Opt>> V);
// From a vector of gf or views (a gf must be contructible from GF2)
template <typename Variable, typename Target, typename Opt, typename GF2>
block_gf<Variable, Target, Opt>
make_block_gf(std::vector<GF2> const &V);
// From a init list of GF with the correct type
template <typename Variable, typename Target, typename Opt>
block_gf<Variable, Target, Opt>
make_block_gf(std::initializer_list<gf<Variable, Target, Opt>> const &V);
// From vector<string> and a gf to be copied
template <typename Variable, typename Target, typename Opt>
block_gf<Variable, Target, Opt>
make_block_gf(std::vector<std::string> block_names, gf<Variable, Target, Opt> const &g);
// From vector<string>, vector<gf>
template <typename Variable, typename Target, typename Opt>
block_gf<Variable, Target, Opt>
make_block_gf(std::vector<std::string> block_names, std::vector<gf<Variable, Target, Opt>> V);
// From vector<string>, init_list<GF>
template <typename Variable, typename Target, typename Opt>
block_gf<Variable, Target, Opt>
make_block_gf(std::vector<std::string> block_names,
std::initializer_list<gf<Variable, Target, Opt>> const &V);
Factories for the view type
.....................................
The factories for the view type *gf_view*, *gf_const_view* are ::
// Build a view of the gf.
// 1- All Green functions must have the same type
// 2- [Expert only] This is a simplified version of the code.
// In the real code, the reference is of stripped from G in the type deduction.
template<typename ... G>
gf_view<block_index, G>
make_block_gf_view(G && ... g);
// Make a view from a vector of gf
template<typename GF>
gf_view<block_index,GF>
make_block_gf_view_from_vector (std::vector<GF> V);
Domain & mesh
----------------
The domain is a discrete domain ...
Singularity
-------------
None.
Interpolation method
---------------------
None.
Data storage
---------------
Not exposed to user.
HDF5 storage convention
---------------------------
TO BE WRITTEN.
Iterators
-----------
TO BE COMPLETED.
Block gf have a natural iterator, e.g. ::
// if a BG is block function
for (auto & g : BG) ....
Examples
---------
.. compileblock::
#include <triqs/gfs.hpp>
using namespace triqs::gfs; using triqs::clef::placeholder;
int main() {
double beta =1;
// Make a block gf of 3 gf, which are empty (default constructed).
auto Bg0 = block_gf<imfreq> (3);
// make a few gf<imfreq> ...
auto g1 = gf<imfreq> ({beta, Fermion}, {2,2});
// ... and construct some block function out of them.
auto Bg1 = make_block_gf<imfreq> (3, g1);
auto Bg2 = make_block_gf<imfreq> ({g1,g1,g1});
auto Bg3 = make_block_gf<imfreq> ({"a","b","c"}, {g1,g1,g1});
// do something on all blocks
for (auto const &g : Bg1) {
std::cout<< g.mesh() << std::endl;
}
// multiply them by 1,2,3 ...
auto i = 1;
for (auto & g : Bg1) g = g * i++;
// a little save in an hdf5 file ?
H5::H5File file("test_block_gf.h5", H5F_ACC_TRUNC );
h5_write(file, "B3", Bg3);
}