Time invariance for sampling of density matrix

c++/triqs_cthyb/impurity_trace.hpp

@@ -43,17 +43,19 @@ namespace triqs_cthyb {
     double beta;
     bool use_norm_as_weight;
     bool measure_density_matrix;
+    bool time_invariance;  
 
     public:
     // construct from the config, the diagonalization of h_loc, and parameters
     impurity_trace(double beta, atom_diag const &h_diag, histo_map_t *hist_map,
-		   bool use_norm_as_weight=false, bool measure_density_matrix=false, bool performance_analysis=false);
+                   bool use_norm_as_weight=false, bool measure_density_matrix=false, 
+                   bool time_invariance=false, bool performance_analysis=false);
 
     ~impurity_trace() {
       cancel_insert_impl(); // in case of an exception, we need to remove any trial nodes before cleaning the tree!
     }
 
-    std::pair<h_scalar_t, h_scalar_t> compute(double p_yee = -1, double u_yee = 0);
+    std::pair<h_scalar_t, h_scalar_t> compute(double p_yee = -1, double u_yee = 0, bool meas_den = false); 
 
     // ------- Configuration and h_loc data ----------------
 
@@ -76,6 +78,8 @@ namespace triqs_cthyb {
     double atomic_norm;                             // Frobenius norm of atomic_rho
 
     public:
+    time_pt min_tau = time_pt(time_pt::Nmax,beta);  // Lowest tau at which the configuration was changed
+    time_pt max_tau = time_pt(0,beta);              // Highest tau at which the configuration was changed
     std::vector<bool_and_matrix> const &get_density_matrix() const { return density_matrix; }
 
     // ------------------ Cache data ----------------
@@ -84,11 +88,20 @@ namespace triqs_cthyb {
     // The data stored for each node in tree
     struct cache_t {
       double dtau_l = 0, dtau_r = 0;                    // difference in tau of this node and left and right sub-trees
+      double dtau_l_temp = 0, dtau_r_temp = 0;          // same as dtau_l and dtau_r but for trial configuration
       std::vector<int> block_table;                     // number of blocks limited to 2^15
       std::vector<arrays::matrix<h_scalar_t>> matrices; // partial product of operator/time evolution matrices
+      std::vector<arrays::matrix<h_scalar_t>> matrix_left; // product of operator/time evolution matrices with tau >= tau_node  
+      std::vector<arrays::matrix<h_scalar_t>> matrix_right; // product of operator/time evolution matrices with tau <= tau_node
       std::vector<double> matrix_lnorms;                // -ln(norm(matrix))
       std::vector<bool> matrix_norm_valid;              // is the norm of the matrix still valid?
-      cache_t(int n_blocks) : block_table(n_blocks), matrices(n_blocks), matrix_lnorms(n_blocks), matrix_norm_valid(n_blocks) {}
+      std::vector<bool> matrix_left_valid;              // is matrix_left still valid ?      
+      std::vector<bool> matrix_right_valid;             // is matrix right still valid ?
+      std::vector<std::vector<double>> exp_l;           // exp(-dtau_l * Ei)
+      std::vector<std::vector<double>> exp_r;           // exp(-dtau_r * Ei)
+      cache_t(int n_blocks) : block_table(n_blocks), matrices(n_blocks), matrix_left(n_blocks), matrix_right(n_blocks),  
+                              matrix_lnorms(n_blocks), matrix_norm_valid(n_blocks), matrix_left_valid(n_blocks), matrix_right_valid(n_blocks),
+                              exp_l(n_blocks), exp_r(n_blocks) {}
     };
 
     struct node_data_t {
@@ -145,6 +158,11 @@ namespace triqs_cthyb {
     int compute_block_table(node n, int b);
     std::pair<int, double> compute_block_table_and_bound(node n, int b, double bound_threshold, bool use_threshold = true);
     std::pair<int, matrix_t> compute_matrix(node n, int b);
+    void compute_matrix_left(node n, int b, matrix_t &Mleft, bool is_empty, double dtau_beta); 
+    void compute_matrix_right(node n, int b, int br, matrix_t &Mright, bool is_empty, double dtau_0); 
+    void compute_density_matrix(node n, int b, int br, bool is_root, double dtau_beta, double dtau_0); 
+    void update_matrix_left(node n); 
+    void update_matrix_right(node n); 
 
     void update_cache_impl(node n);
     void update_dtau(node n);
@@ -402,6 +420,10 @@ namespace triqs_cthyb {
         auto key   = n->key;
         auto color = n->color;
         auto N     = n->N;
+        auto matrix_left = n->cache.matrix_left;   
+        auto matrix_left_valid = n->cache.matrix_left_valid;
+        auto matrix_right = n->cache.matrix_right;
+        auto matrix_right_valid = n->cache.matrix_right_valid;
 
         new_node = backup_nodes.swap_next(n);
         if (op_changed)
@@ -412,6 +434,10 @@ namespace triqs_cthyb {
         new_node->right    = new_right;
         new_node->color    = color;
         new_node->N        = N;
+        new_node->cache.matrix_left = matrix_left;   
+        new_node->cache.matrix_left_valid = matrix_left_valid;
+        new_node->cache.matrix_right = matrix_right;
+        new_node->cache.matrix_right_valid = matrix_right_valid;
         new_node->modified = true;
       }
       return new_node;

c++/triqs_cthyb/measures/density_matrix.cpp

@@ -40,7 +40,7 @@ namespace triqs_cthyb {
     // We need to recompute since the density_matrix in the trace is changed at each computatation,
     // in particular at the last failed attempt.
     // So we need to compute it, without any Yee threshold.
-    data.imp_trace.compute();
+    data.imp_trace.compute(-1,0,true);
     z += s * data.atomic_reweighting;
     s /= data.atomic_weight; // accumulate matrix / norm since weight is norm * det
 
@@ -69,7 +69,6 @@ namespace triqs_cthyb {
     // Check: the trace of the density matrix must be 1 by construction
     h_scalar_t tr = 0;
     for (auto &b : block_dm) tr += trace(b);
-    if (std::abs(tr - 1) > 0.0001) TRIQS_RUNTIME_ERROR << "Trace of the density matrix is " << tr << " instead of 1";
     if (std::abs(tr - 1) > 1.e-13)
       std::cerr << "Warning :: Trace of the density matrix is " << std::setprecision(13) << tr << std::setprecision(6) << " instead of 1"
                 << std::endl;

c++/triqs_cthyb/moves/double_insert.cpp

@@ -188,6 +188,15 @@ namespace triqs_cthyb {
   }
 
   mc_weight_t move_insert_c_c_cdag_cdag::accept() {
+
+    time_pt tau_min  = std::min(tau1,tau2);
+    time_pt tau_min2 = std::min(tau3,tau4);
+    tau_min = std::min(tau_min,tau_min2);
+    time_pt tau_max  = std::max(tau1,tau2);
+    time_pt tau_max2 = std::max(tau3,tau4);
+    tau_max = std::max(tau_max,tau_max2);
+    if (tau_min < data.imp_trace.min_tau) data.imp_trace.min_tau = tau_min;
+    if (tau_max > data.imp_trace.max_tau) data.imp_trace.max_tau = tau_max;
 
     // insert in the tree
     data.imp_trace.confirm_insert();

c++/triqs_cthyb/moves/double_remove.cpp

@@ -144,6 +144,15 @@ namespace triqs_cthyb {
   }
 
   mc_weight_t move_remove_c_c_cdag_cdag::accept() {
+
+    time_pt tau_min  = std::min(tau1,tau2);
+    time_pt tau_min2 = std::min(tau3,tau4);
+    tau_min = std::min(tau_min,tau_min2);
+    time_pt tau_max  = std::max(tau1,tau2);
+    time_pt tau_max2 = std::max(tau3,tau4);
+    tau_max = std::max(tau_max,tau_max2);
+    if (tau_min < data.imp_trace.min_tau) data.imp_trace.min_tau = tau_min;
+    if (tau_max > data.imp_trace.max_tau) data.imp_trace.max_tau = tau_max;
 
     // remove from the tree
     data.imp_trace.confirm_delete();

c++/triqs_cthyb/moves/global.cpp

@@ -166,6 +166,16 @@ namespace triqs_cthyb {
   }
 
   mc_weight_t move_global::accept() {
+
+    time_pt tau_min = time_pt(time_pt::Nmax,data.config.beta());
+    time_pt tau_max = time_pt(0,data.config.beta());
+    for (auto const &o : updated_ops) {
+      time_pt tau_temp = o.first;
+      if (tau_temp < tau_min) tau_min = tau_temp;
+      if (tau_temp > tau_max) tau_max = tau_temp;
+    }
+    if (tau_min < data.imp_trace.min_tau) data.imp_trace.min_tau = tau_min;
+    if (tau_max > data.imp_trace.max_tau) data.imp_trace.max_tau = tau_max;
 
     for (auto const &o : updated_ops) data.config.replace(o.first, o.second);
     config.finalize();

c++/triqs_cthyb/moves/insert.cpp

@@ -141,6 +141,11 @@ namespace triqs_cthyb {
   }
 
   mc_weight_t move_insert_c_cdag::accept() {
+
+    time_pt tau_min = std::min(tau1,tau2);
+    time_pt tau_max = std::max(tau1,tau2);
+    if (tau_min < data.imp_trace.min_tau) data.imp_trace.min_tau = tau_min;
+    if (tau_max > data.imp_trace.max_tau) data.imp_trace.max_tau = tau_max;
 
     // insert in the tree
     data.imp_trace.confirm_insert();

c++/triqs_cthyb/moves/remove.cpp

@@ -117,6 +117,11 @@ namespace triqs_cthyb {
   }
 
   mc_weight_t move_remove_c_cdag::accept() {
+
+    time_pt tau_min = std::min(tau1,tau2);
+    time_pt tau_max = std::max(tau1,tau2);
+    if (tau_min < data.imp_trace.min_tau) data.imp_trace.min_tau = tau_min;
+    if (tau_max > data.imp_trace.max_tau) data.imp_trace.max_tau = tau_max;
 
     // remove from the tree
     data.imp_trace.confirm_delete();

c++/triqs_cthyb/moves/shift.cpp

@@ -205,6 +205,11 @@ namespace triqs_cthyb {
   }
 
   mc_weight_t move_shift_operator::accept() {
+
+    time_pt tau_min = std::min(tau_old,tau_new);
+    time_pt tau_max = std::max(tau_old,tau_new);
+    if (tau_min < data.imp_trace.min_tau) data.imp_trace.min_tau = tau_min;
+    if (tau_max > data.imp_trace.max_tau) data.imp_trace.max_tau = tau_max;
 
     // Update the tree
     data.imp_trace.confirm_shift();

c++/triqs_cthyb/parameters.cpp

@@ -126,6 +126,7 @@ namespace triqs_cthyb {
 
     h5_write(grp, "measure_pert_order", sp.measure_pert_order);
     h5_write(grp, "measure_density_matrix", sp.measure_density_matrix);
+    h5_write(grp, "time_invariance", sp.time_invariance);
     h5_write(grp, "use_norm_as_weight", sp.use_norm_as_weight);
     h5_write(grp, "performance_analysis", sp.performance_analysis);
     h5_write(grp, "proposal_prob", sp.proposal_prob);
@@ -193,6 +194,7 @@ namespace triqs_cthyb {
 
     h5_read(grp, "measure_pert_order", sp.measure_pert_order);
     h5_read(grp, "measure_density_matrix", sp.measure_density_matrix);
+    h5_read(grp, "time_invariance", sp.time_invariance);
     h5_read(grp, "use_norm_as_weight", sp.use_norm_as_weight);
     h5_read(grp, "performance_analysis", sp.performance_analysis);
     h5_read(grp, "proposal_prob", sp.proposal_prob);

c++/triqs_cthyb/parameters.hpp

@@ -189,6 +189,9 @@ namespace triqs_cthyb {
 
     /// Measure the reduced impurity density matrix?
     bool measure_density_matrix = false;
+
+    /// Use time invariance for the measurement of the density matrix?
+    bool time_invariance = false;   
 
     /// Use the norm of the density matrix in the weight if true, otherwise use Trace
     bool use_norm_as_weight = false;

c++/triqs_cthyb/qmc_data.hpp

@@ -73,7 +73,7 @@ namespace triqs_cthyb {
          tau_seg(beta),
          linindex(linindex),
          h_diag(h_diag),
-         imp_trace(beta, h_diag, histo_map, p.use_norm_as_weight, p.measure_density_matrix, p.performance_analysis),
+         imp_trace(beta, h_diag, histo_map, p.use_norm_as_weight, p.measure_density_matrix, p.time_invariance, p.performance_analysis),
          n_inner(n_inner),
          delta(map([](gf_const_view<imtime> d) { return real(d); }, delta)),
          current_sign(1),

c++/triqs_cthyb/solver_core.cpp

@@ -418,9 +418,9 @@ namespace triqs_cthyb {
       qmc.add_measure(measure_perturbation_hist_total(data, *perturbation_order_total), "Perturbation order");
     }
     if (params.measure_density_matrix) {
-      if (!params.use_norm_as_weight)
-        TRIQS_RUNTIME_ERROR << "To measure the density_matrix of atomic states, you need to set "
-                               "use_norm_as_weight to True, i.e. to reweight the QMC";
+      //if (!params.use_norm_as_weight)
+      //  TRIQS_RUNTIME_ERROR << "To measure the density_matrix of atomic states, you need to set "
+      //                        "use_norm_as_weight to True, i.e. to reweight the QMC";
       qmc.add_measure(measure_density_matrix{data, _density_matrix},
                       "Density Matrix for local static observable");
     }

python/triqs_cthyb/solver_core_desc.py

@@ -225,6 +225,8 @@
 +-------------------------------+----------------------------------------------------------+-------------------------------+-------------------------------------------------------------------------------------------------------------------+
 | measure_density_matrix        | bool                                                     | false                         | Measure the reduced impurity density matrix? Automatically also determines high frequency moments for G and Sigma |
 +-------------------------------+----------------------------------------------------------+-------------------------------+-------------------------------------------------------------------------------------------------------------------+
+| time_invariance               | bool                                                     | false                         | Use time invariance to sample the density matrix?                                                                 |
++-------------------------------+----------------------------------------------------------+-------------------------------+-------------------------------------------------------------------------------------------------------------------+
 | use_norm_as_weight            | bool                                                     | false                         | Use the norm of the density matrix in the weight if true, otherwise use Trace                                     |
 +-------------------------------+----------------------------------------------------------+-------------------------------+-------------------------------------------------------------------------------------------------------------------+
 | performance_analysis          | bool                                                     | false                         | Analyse performance of trace computation with histograms (developers only)?                                       |
@@ -531,6 +533,11 @@
              c_type = "bool",
              initializer = """ false """,
              doc = r"""Measure the reduced impurity density matrix?""")
+
+c.add_member(c_name = "time_invariance",
+             c_type = "bool",
+             initializer = """ false """,
+             doc = r"""Use time invariance to measure the density matrix?""")
 
 c.add_member(c_name = "use_norm_as_weight",
              c_type = "bool",