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80 lines
4.7 KiB
ReStructuredText
80 lines
4.7 KiB
ReStructuredText
.. highlight:: c
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.. _option_template:
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Options template parameters
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The `Option::options` template can take several parameters that determine various aspects of `array` (resp. `matrix`, `vector`) at **compile time**.
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These parameters can be given in any order in the `options` template, but only at most only (they all have a default, that can also be changed
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using macros for maximum flexibility).
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These options parameters determine :
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* the storage order of indices in memory at **compile time**.
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=============================== ===========================================================================================
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Template parameter Meaning
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=============================== ===========================================================================================
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`Tag::C` `[default]` C-style order
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`Tag::Fortran` Fortran-style order ( NB the base index is still 0, not 1 !)
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memory_order<i0,i1,i2,... > The tuple <i0,i1,i2...> of size rank determines the storage order of indices in memory
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memory_order_p<P> P is a triqs::arrays::Permutations::permutation that determines the storage order in memory
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P[0] is the fastest index, P[rank - 1] the slowest index
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=============================== ===========================================================================================
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Example of custom order ::
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custom<Permutation<0,1,2> > // same as index_order_Fortran, the first index is the fastest
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custom<Permutation<2,1,0> > // same as index_order_C, the last index is the fastest
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custom<Permutation<1,2,0> > // if indices are (i,j,k) : index j is fastest, then k, then i
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* whether bound check are done while accessing array elements or slicing the arrays.
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=============================== ====================================================================================================
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Template parameter Meaning
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=============================== ====================================================================================================
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`Tag::NoBoundCheck` `[default]` Do no bound check at all. This is the default, for speed !
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`Tag::BoundCheck` Do bound checks. Boundary errors throw triqs::arrays::key_error exception (See ??)
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=============================== ====================================================================================================
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The macro `TRIQS_ARRAYS_ENFORCE_BOUNDCHECK` change the default to `Tag::BoundCheck` (for debugging purposes).
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Rational : one may want for some array to activate bound check and catch the exception, while keeping faster unchecked arrays elsewhere.
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* whether arrays are initialized at construction.
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=============================== ====================================================================================================
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Template parameter Meaning
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=============================== ====================================================================================================
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`Tag::no_init` `[default]` No initialization of the array at construction (fastest).
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`Tag::default_init` Initialize with the default constructor of ValueType
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`Tag::nan_inf_init` Initialize to nan for floating type and std::limits<ValueType>::infinity() for integer type
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as in D e.g. mainly for detecting easily lack of initialization errors.
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=============================== ====================================================================================================
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Note that :
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* The macro `TRIQS_ARRAYS_ENFORCE_INIT_NAN_INF` change the default to `Tag::nan_inf_init`.
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* The macro `TRIQS_ARRAYS_ENFORCE_INIT_DEFAULT` change the default to `Tag::default_init`.
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* Several simple aliases are defined in the namespace Option for the most current cases :
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=============================== ===============================
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Option aliases
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=============================== ===============================
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Option::C Option::options<`Tag::C`>
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Option::Default Option::options<`Tag::C`>
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Option::Fortran Option::options<`Tag::Fortran>`
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=============================== ===============================
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* Examples ::
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array<long, 3, Option::options<Option::memory_order <2,1,0> > > A0 (2,3,4);
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array<long, 3, Option::options<Option::memory_order <0,1,2> > > A1 (2,3,4);
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array<long, 3, Option::options<Option::memory_order <1,0,2> > > A2 (2,3,4);
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array<long, 3, Option::Fortran > A4 (2,3,4);
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