compute rank using floor function

src/moves.cpp

@@ -323,6 +323,7 @@ Rcpp::List cpp_move_alpha(Rcpp::List param, Rcpp::List data, Rcpp::List config,
   double old_loglike = 0.0, new_loglike = 0.0, p_accept = 0.0;
   Rcpp::IntegerVector possible_ancestors;
   Rcpp::IntegerVector t_inf_i;
+  int rank;
 
   for (int i = 0; i < N; i++) {
     if (alpha[i] == NA_INTEGER ){
@@ -355,8 +356,9 @@ Rcpp::List cpp_move_alpha(Rcpp::List param, Rcpp::List data, Rcpp::List config,
         // loglike with current value
         old_loglike = cpp_ll_all(data, config, param, i+1, list_custom_ll); // offset
         // proposal (+/- 1)
-        new_alpha[i] = possible_ancestors[unif_rand() * possible_ancestors.size()];
-        new_kappa[i] = unif_rand() * K + 1;
+        rank = floor(unif_rand() * possible_ancestors.size());
+        new_alpha[i] = possible_ancestors[rank];
+        new_kappa[i] = floor(unif_rand() * K) + 1;
         // loglike with current value
         new_loglike = cpp_ll_all(data, config, new_param, i+1, list_custom_ll);
 
@@ -445,7 +447,7 @@ Rcpp::List cpp_move_ancestors(Rcpp::List param, Rcpp::List data, Rcpp::List conf
 
   double old_loglike = 0.0, new_loglike = 0.0, p_accept = 0.0, runif = 0.0;
   Rcpp::IntegerVector all_desc;
-  int j_clust;
+  int j_clust, rank_ances, rank_index;
 
   for (int i = 0; i < N; i++) {
     if (alpha[i] == NA_INTEGER ){
@@ -479,7 +481,8 @@ Rcpp::List cpp_move_ancestors(Rcpp::List param, Rcpp::List data, Rcpp::List conf
       size_t new_ances;
       Rcpp::IntegerVector possible_index;
       if (possible_ances.size()>0){
-        new_ances = possible_ances[unif_rand()*possible_ances.size()];
+        rank_ances = floor(unif_rand() * possible_ances.size());
+        new_ances = possible_ances[rank_ances];
 
         new_alpha[new_ances-1] = NA_INTEGER;
 
@@ -492,8 +495,9 @@ Rcpp::List cpp_move_ancestors(Rcpp::List param, Rcpp::List data, Rcpp::List conf
           changes[1] = new_ances;
           old_loglike = cpp_ll_all(data, config, param, changes, list_custom_ll); 
 
-          size_t new_index = possible_index[unif_rand() * possible_index.size()];
-
+          rank_index = floor(unif_rand() * possible_index.size());
+          size_t new_index = possible_index[rank_index];
+
           new_alpha[i] = new_index;
           new_kappa[i] = new_kappa[new_ances-1];
           new_kappa[new_ances-1] = NA_INTEGER;
@@ -604,10 +608,9 @@ Rcpp::List cpp_move_swap_cases(Rcpp::List param, Rcpp::List data,
   Rcpp::IntegerVector swap_alpha, swap_t_inf, swap_kappa;
   Rcpp::List swapinfo; // contains alpha, kappa and t_inf
   Rcpp::IntegerVector local_cases, descendents, desc_i_swap;
-  Rcpp::IntegerVector tree_i, tree_j;
   Rcpp::String gen_tree, gen_tree_j;
   Rcpp::IntegerVector vec_swap(N);
-  int vect_k, i_swap, size_descendents, n_loc, i, k, j_clust;
+  int vect_k, i_swap, size_descendents, n_loc, i, k, j_clust, rank;
   double old_loglike = 0.0, new_loglike = 0.0, p_accept = 0.0;
 
   Rcpp::StringVector all_gen = clone(genotype); // copy of data$genotype
@@ -629,7 +632,8 @@ Rcpp::List cpp_move_swap_cases(Rcpp::List param, Rcpp::List data,
 
       descendents = cpp_find_descendents(alpha, cluster_i, i+1);
       size_descendents = descendents.size();
-      i_swap = descendents[unif_rand() * size_descendents];
+      rank = floor(unif_rand() * size_descendents);
+      i_swap = descendents[rank];
       // The local likelihood is defined as the likelihood computed for the
       // cases affected by the swap; these include:
       // - 'i_swap' 
@@ -695,7 +699,7 @@ Rcpp::List cpp_move_swap_cases(Rcpp::List param, Rcpp::List data,
         }
 
         if(swap_ances.size() > 0){
-          i_swap = swap_ances[unif_rand() * swap_ances.size()];
+          i_swap = swap_ances[floor(unif_rand() * swap_ances.size())];
           desc_i_swap = cpp_find_descendents(alpha, cluster_i, i_swap);
 
           int t_inf_i = new_t_inf[i];