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83 lines
3.8 KiB
ReStructuredText
83 lines
3.8 KiB
ReStructuredText
.. _montecarloref:
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Full reference
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--------------
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Introduction & Motivations
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**************************
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* **Purpose** :
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The purpose of this little class is too facilitate the writing and maintenance
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of Metropolis MonteCarlo algorithms, with several **advantages** :
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* Easy to add new moves and measures.
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* For complex MC algorithms, with 6 or 7 different moves, it helps to clearly separate the code for each move.
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* Parallelism is automatic.
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* The random generator is a simple parameter, it can be chosen dynamically.
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* **Principle**
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The `mc_generic` class is a generic version of the algorithms, with `moves` and `measures`.
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The user :
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- writes move classes, modelling the Move concept.
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- writes measure classes, modelling the Measure concepts.
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- register them in a mc_generic object MC
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- call `MC.start(...)` ... and that is (almost) it !
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The Move concept
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****************
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========================== =============================================================================================
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Elements Comment
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========================== =============================================================================================
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* mc_sign_type attempt() - First part of the Move.
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- Returns the probability to accept the move. If :
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- the move is :math:`x\rightarrow x'`, proposed with proba :math:`T_{x\rightarrow x'}`
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- the probability of the :math:`x` config is denoted :math:`p_x`
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- then attempt should return the Metropolis ratio:
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.. math::
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\frac{p_{x'} T_{x'\rightarrow x}}{p_x T_{x\rightarrow x'}}
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with the sign. (The sign will be separated from the absolute value and kept by the MonteCarlo class).
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In other words: attempt() = move_sign * move_rate with abs(move_sign) = 1
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* mc_sign_type accept() - Called iif the Move is accepted.
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- Returns a number r such that :math:`|r| =1`
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- There is a possibility to update the sign
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here as well, so that the final sign is: move_sign * accept()
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- CAREFUL that we need the ratio new_sign / old_sign here just like
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we needed a ratio in attempt()
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* void reject() - Called iif the Move is rejected (for cleaning).
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========================== =============================================================================================
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The Measure concept
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*******************
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========================================================================== ============================================================
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Elements Comment
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========================================================================== ============================================================
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* void accumulate(std::complex<double> sign) - Accumulation with the sign
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* void collect_results ( boost::mpi::communicator const & c) - Collects the results over the communicator, and finalize
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the calculation (compute average, error).
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========================================================================== ============================================================
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Doxygen documentation
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*********************
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The :doxy:`full C++ documentation<triqs::mc_tools::mc_generic>` is available here.
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.. :
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Breathe Documentation
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*********************
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.. doxygenclass:: triqs::mc_tools::mc_generic
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:project: doxy
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:members:
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