mirror of
https://github.com/triqs/dft_tools
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77 lines
2.2 KiB
ReStructuredText
77 lines
2.2 KiB
ReStructuredText
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swap & deep_swap
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==================================
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There are two possible interpretation of "swapping two arrays" :
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either use 3 moves like std::swap, i.e. swapping the pointer to the data in memory,
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or making a deep swap, i.e. really swapping all the elements in memeory.
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.. _arr_swap:
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swap
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--------
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* swap just exchange the (shared) pointer to the data in memory,
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it does not affect the data them self.
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This distinction of importance for views in particular.
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* For the regular type, std::swap and swap are equivalent.
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For the views, std::swap is explicitely deleted, since it is incorrect
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due to the lack of move constructor for a view.
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Use `swap` instead.
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* **Example** :
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.. compileblock::
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#include <triqs/arrays.hpp>
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#include <iostream>
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using triqs::arrays::vector; using triqs::arrays::range;
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int main () {
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triqs::arrays::vector<double> V(3), W(4);
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V() = 3; W()=4; // initialize
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auto VV = V(range (0,2));
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auto VW = W(range (0,2));
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std::cout << "V = "<< V << " W = " << W<< " V view "<< VV<< " W view "<< VW<< std::endl;
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swap(V,W);
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std::cout << "V = "<< V << " W = " << W<< " V view "<< VV<< " W view "<< VW<< std::endl;
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swap(VV,VW);
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std::cout << "V = "<< V << " W = " << W<< " V view "<< VV<< " W view "<< VW<< std::endl;
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}
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.. _arr_deep_swap:
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deep_swap
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--------------
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.. warning::
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Currently implemented only for triqs::vector and triqs::vector_view.
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* deep_swap swaps the data in memory.
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* **Example** (compare with swap) :
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.. compileblock::
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#include <triqs/arrays.hpp>
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#include <iostream>
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using triqs::arrays::vector; using triqs::arrays::range;
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int main () {
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triqs::arrays::vector<double> V(3), W(3);
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V() = 3; W()=5; // initialize
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auto VV = V(range (0,2));
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auto VW = W(range (0,2));
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std::cout << "V = "<< V << " W = " << W<< " V view "<< VV<< " W view "<< VW<< std::endl;
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deep_swap(V,W);
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std::cout << "V = "<< V << " W = " << W<< " V view "<< VV<< " W view "<< VW<< std::endl;
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deep_swap(VV,VW);
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std::cout << "V = "<< V << " W = " << W<< " V view "<< VV<< " W view "<< VW<< std::endl;
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}
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