From d5baabbeda7775f76d89032a1961c92434e5d770 Mon Sep 17 00:00:00 2001
From: Amrita Goswami <amrita16thaug646@gmail.com>
Date: Wed, 20 Mar 2024 16:17:59 +0000
Subject: [PATCH] Deffuant: Model with square lattice neighbours

Implemented the Deffuant model with a square lattice neighbour list.
TODO: Actually parse these options.

Co-authored-by: Moritz Sallermann <moritzsallermann@gmail.com>
---
 include/models/DeffuantModel.hpp |  8 +++++--
 src/models/DeffuantModel.cpp     | 38 ++++++++++++++++++++++++++++----
 2 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/include/models/DeffuantModel.hpp b/include/models/DeffuantModel.hpp
index 2cba82d..3a472db 100644
--- a/include/models/DeffuantModel.hpp
+++ b/include/models/DeffuantModel.hpp
@@ -19,8 +19,9 @@ class DeffuantModel : public Model<SimpleAgent>
     using AgentT   = SimpleAgent;
     using NetworkT = Network<AgentT>;
 
-    double homophily_threshold = 0.2; // d in paper
-    double mu                  = 0.5; // convergence parameter
+    double homophily_threshold = 0.2;   // d in paper
+    double mu                  = 0.5;   // convergence parameter
+    bool use_network           = false; // for the basic Deffuant model
 
     DeffuantModel( NetworkT & network, std::mt19937 & gen );
 
@@ -30,6 +31,9 @@ class DeffuantModel : public Model<SimpleAgent>
 private:
     NetworkT & network;
     std::mt19937 & gen; // reference to simulation Mersenne-Twister engine
+
+    // Select interacting agents
+    std::vector<std::size_t> select_interacting_agent_pair();
 };
 
 } // namespace Seldon
\ No newline at end of file
diff --git a/src/models/DeffuantModel.cpp b/src/models/DeffuantModel.cpp
index c4c6308..a717434 100644
--- a/src/models/DeffuantModel.cpp
+++ b/src/models/DeffuantModel.cpp
@@ -18,6 +18,39 @@ DeffuantModel::DeffuantModel( NetworkT & network, std::mt19937 & gen )
     }
 }
 
+std::vector<std::size_t> DeffuantModel::select_interacting_agent_pair()
+{
+
+    auto interacting_agents = std::vector<std::size_t>();
+
+    // If the basic model is being used, then search from all possible agents
+    if( !use_network )
+    {
+
+        // Pick any two agents to interact, randomly, without repetition
+        draw_unique_k_from_n( std::nullopt, 2, network.n_agents(), interacting_agents, gen );
+
+        return interacting_agents;
+    }
+    else
+    {
+        // First select an agent randomly
+        auto dist       = std::uniform_int_distribution<size_t>( 0, network.n_agents() - 1 );
+        auto agent1_idx = dist( gen );
+        interacting_agents.push_back( agent1_idx );
+
+        // Choose a neighbour randomly from the neighbour list of agent1_idx
+        auto neighbours     = network.get_neighbours( agent1_idx );
+        auto n_neighbours   = neighbours.size();
+        auto dist_n         = std::uniform_int_distribution<size_t>( 0, n_neighbours - 1 );
+        auto index_in_neigh = dist_n( gen ); // Index inside neighbours list
+        auto agent2_idx     = neighbours[index_in_neigh];
+        interacting_agents.push_back( agent2_idx );
+
+        return interacting_agents;
+    }
+}
+
 void DeffuantModel::iteration()
 {
     Model<AgentT>::iteration(); // Update n_iterations
@@ -28,10 +61,7 @@ void DeffuantModel::iteration()
     for( size_t i = 0; i < network.n_agents(); i++ )
     {
 
-        auto interacting_agents = std::vector<std::size_t>();
-
-        // Pick any two agents to interact, randomly, without repetition
-        draw_unique_k_from_n( std::nullopt, 2, network.n_agents(), interacting_agents, gen );
+        auto interacting_agents = select_interacting_agent_pair();
 
         auto & agent1 = network.agents[interacting_agents[0]];
         auto & agent2 = network.agents[interacting_agents[1]];