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https://github.com/triqs/dft_tools
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140 lines
6.9 KiB
ReStructuredText
140 lines
6.9 KiB
ReStructuredText
.. highlight:: c
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array and array_view : declaration & construction
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====================================================================================================================
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array and array_view :
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* are the standard d-dimensional cuboid array and the corresponding view.
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* allow **custom memory ordering** at compile time.
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* model the :ref:`HasImmutableArrayInterface` concept.
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Template parameters
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----------------------------
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* The classes have three template parameters.
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.. code-block:: c
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template <typename ValueType, int Rank, typename Opt= Option::Default > class array_view;
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template <typename ValueType, int Rank, typename Opt= Option::Default > class array;
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============================ ================================== ========================== ====================================================================
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Template parameter Accepted type Access in the class Meaning
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============================ ================================== ========================== ====================================================================
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ValueType normally a scalar, but any default value_type The type of the element of the array
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constructible type (?).
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Rank int rank The rank of the array
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Opt Option::options< ...> opt_type Compile time options, see below.
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============================ ================================== ========================== ====================================================================
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Options template parameters are described :ref:`here <option_template>`.
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.. _array_constructors:
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Constructors of array
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---------------------------
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========================================== ===========================================================================================
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Constructors of array Comments
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========================================== ===========================================================================================
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array() - Empty array of size 0
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array(const array &) - Copy constructor
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array(array &&) - Move constructor
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array(size_t, ...., size_t) - From the dimensions [number of parameters checked at compile time].
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Does **NOT** initialize the array elements to 0 ! (see compile time option)
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Use my_array() =0 to do it explicitely.
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array(cuboid_domain<rank> const &) - New array with the corresponding domain
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array(PyObject * X) - Construct a new array from the Python object X.
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NB : X is a borrowed reference, array does affect its counting reference.
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- it takes a **copy** of the data of X (or of numpy(X)) into C++.
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- X is first transformed into a numpy by the python numpy lib itself
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(as if you call numpy.array(X)) if X is not a numpy array or an array of the wrong type
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(e.g. you construct an array<double,2> from a numpy of int....), and
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copied into the array.
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array(const T & X) - Type T models the :ref:`HasImmutableArrayInterface` concept.
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- X must have the appropriate domain (checked at compile time).
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- Constructs a new array of domain X.domain() and fills it with evaluation of X.
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========================================== ===========================================================================================
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.. warning::
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The constructor from the dimensions does **NOT** initialize the matrix to 0
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(because it may not be optimal).
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If needed, do it explicitely by (a if the array) `a()=0`;
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- LAYOUT
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Examples
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------------
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.. compileblock::
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#include <triqs/arrays.hpp>
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using triqs::arrays::array; using triqs::arrays::matrix;
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using triqs::arrays::vector; using triqs::arrays::permutation;
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int main(){
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// A 3d array of long, C ordering, no option
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array<long, 3> A3(1,2,3);
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// A 2d array of double, C ordering, with explicit Bound Checking
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array<double, 2> B(1,2);
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// a matrix of long
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matrix<long> M(2,2);
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// a vector of double
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vector<double> V(10);
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// arrays with custom TraversalOrder
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// C-style
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array<long, 3, 0, permutation(2,1,0)> A0(2,3,4);
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array<long, 3, 0> A0b; // same type but empty
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// Fortran-style
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array<long, 3, TRAVERSAL_ORDER_FORTRAN> A4 (2,3,4);
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array<long, 3, 0, permutation(0,1,2)> A1b(); //same type but empty
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// custom : (i,j,k) : index j is fastest, then k, then i
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array<long, 3, 0, permutation(1,0,2)> A2(2,3,4);
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}
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Constructors of array_views
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----------------------------------------------
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Automatic construction
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^^^^^^^^^^^^^^^^^^^^^^^^^^^
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array_view are normally automatically constructed by making (partial) views, ref:`Slicing`, e.g. ::
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array<int,2> A(2,2);
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A(range(),2) ; // --> this makes a view...
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A() ; // --> this makes a view over the full array
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Explicit construction
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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To explicitly make a view of an array, use make_view or the ()::
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array<int,2> A(2,2);
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make_view(A); //-> a view...
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make_view(A) = 13 ; // to assign e.g.
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A() = 13; // same thing...
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====================================================================== =====================================================================================================
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Constructors of array_view Comments
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====================================================================== =====================================================================================================
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array_view(const array_view &) - Copy construction (shallow copy)
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array_view(const T & X) - `[Advanced]` T is any type such that X.indexmap() and X.storage() can be used to construct a view.
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array_view(indexmap_type const & I, S_type const &) - `[Advanced]` From a couple of indexmap I and storage of type S_type.
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====================================================================== =====================================================================================================
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