mirror of
https://github.com/triqs/dft_tools
synced 2024-12-26 22:33:48 +01:00
4af1afbdaf
- For users : only change is :
H5::H5File in apps. to be replaced by triqs::h5::file, same API.
- using only the C API because :
- it is cleaner, better documented, more examples.
- it is the native hdf5 interface.
- simplify the installation e.g. on mac. Indeed, hdf5 is
usually installed without C++ interface, which is optional.
E.g. EPD et al., brew by default.
Also the infamous mpi+ hdf5_cpp bug, for which we have no clean solution.
- clean the notion of parent of a group. Not needed, better iterate function in C LT API.
- modified doc : no need for C++ bindings any more.
- modified cmake to avoid requiring CPP bindings.
112 lines
4.2 KiB
C++
112 lines
4.2 KiB
C++
// The goal of this program is to give an example of the use of the probability for proposing a move (here, pl and pr)
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// The walker try to go towards its left with probability 2*pl/(pl+pr) (pl is given to the move_left constructor),
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// or towards the right with probability 2*pr/(pl+pr) (pr is given to the move_right constructor).
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// The left move is accepted with probability proba=pr/pl and the right move with probability proba=pl/pr (in reality, each time with probability min(1,proba) ).
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// A python notebook is associated to this example, with the comparison to the theoretical gaussian histogram.
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#define TRIQS_ARRAYS_ENFORCE_BOUNDCHECK
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#include <triqs/utility/callbacks.hpp>
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#include <triqs/mc_tools/mc_generic.hpp>
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namespace h5 = triqs::h5;
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triqs::arrays::array<std::complex<double>,1> make_array( std::complex<double> c){return {c}; };
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struct configuration {
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int x; //position of the walker
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configuration():x(0){} //constructor
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};
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//------------------------------------------------------------
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// MOVES
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//------------------------------------------------------------
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struct move_left {
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configuration *config;
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double proba;
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triqs::mc_tools::random_generator &RND;
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move_left(configuration &config_, double pl, double pr, triqs::mc_tools::random_generator &RND_):config(&config_), proba(pr/pl), RND(RND_){} //constructor
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double attempt() {return proba; }
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double accept() {config->x += -1; return 1; }
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void reject() {}
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};
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struct move_right {
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configuration *config;
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double proba;
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triqs::mc_tools::random_generator &RND;
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move_right( configuration &config_, double pl, double pr, triqs::mc_tools::random_generator &RND_):config(&config_), proba(pl/pr), RND(RND_){} //constructor
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double attempt() {return proba; }
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double accept() {config->x += 1; return 1; }
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void reject() {}
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};
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//------------------------------------------------------------
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// MEASUREMENTS
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//------------------------------------------------------------
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struct compute_histo{
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configuration *config;
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triqs::arrays::array<double,1> H; // an histogram
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int xmax, tot;
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compute_histo(configuration &config_, triqs::arrays::array<double,1> &H_, int xmax_) : config(&config_), H(H_), xmax(xmax_), tot(0) {}
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void accumulate(double sign) {
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if( config->x+xmax>=0 && config->x-xmax<0){
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H( floor( (config->x+xmax) ) ) += 1;
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tot += 1;
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}
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config->x=0;
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}
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void collect_results(boost::mpi::communicator const &c) {
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H/=tot;
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h5::file file("histo.h5",H5F_ACC_TRUNC);
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h5_write(file,"H",H);
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}
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};
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//------------------------------------------------------------
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// MAIN
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//------------------------------------------------------------
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int main(int argc, char* argv[]) {
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// initialize mpi
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boost::mpi::environment env(argc, argv);
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boost::mpi::communicator world;
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// greeting
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if (world.rank() == 0) std::cout << "Random walk calculation" << std::endl;
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// prepare the MC parameters
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int N_Cycles = 100000;
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int Length_Cycle = 100;
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int N_Warmup_Cycles = 0;
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std::string Random_Name = "";
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int Random_Seed = 374982 + world.rank() * 273894;
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int Verbosity = (world.rank() == 0 ? 3 : 0);
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int xmax=floor(4*sqrt(Length_Cycle) ); //max of the position registered in the histogram
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double pl=1.5, pr=1; //non normalized probabilities for proposing a left or right move
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h5::file file("params.h5",H5F_ACC_TRUNC);
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h5_write(file,"pr",make_array(pr));
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h5_write(file,"pl",make_array(pl));
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h5_write(file,"xmax",make_array(xmax));
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h5_write(file,"N_Cycles",make_array(N_Cycles));
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h5_write(file,"Length_Cycle",make_array(Length_Cycle));
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// construct a Monte Carlo loop
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triqs::mc_tools::mc_generic<double> IntMC(N_Cycles, Length_Cycle, N_Warmup_Cycles, Random_Name, Random_Seed, Verbosity);
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// construct configuration
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configuration config;
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triqs::arrays::array<double,1> H(2*xmax);
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H()=0;
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// add moves and measures
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IntMC.add_move(move_left (config, pl, pr, IntMC.rng() ), "left move", pl);
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IntMC.add_move(move_right(config, pl, pr, IntMC.rng() ), "right move", pr);
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IntMC.add_measure(compute_histo(config, H, xmax), "histogramn measure");
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// Run and collect results
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IntMC.start(1.0, triqs::utility::clock_callback(600));
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IntMC.collect_results(world);
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return 0;
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}
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