diff --git a/Cargo.toml b/Cargo.toml
index f8d3b03..b5d70a3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,7 +7,6 @@ edition = "2021"
 
 [dependencies]
 
-petgraph = "*"
 ndarray = "*"
 thiserror = "*"
 rand = "*"
diff --git a/src/ctbn.rs b/src/ctbn.rs
index 6e5f0b4..0bdd575 100644
--- a/src/ctbn.rs
+++ b/src/ctbn.rs
@@ -1,6 +1,5 @@
 use std::collections::{HashMap, BTreeSet};
-use petgraph::prelude::*;
-
+use ndarray::prelude::*;
 use crate::node;
 use crate::params::StateType;
 use crate::network;
@@ -9,50 +8,80 @@ use crate::network;
 
 
 pub struct CtbnNetwork {
-    network: petgraph::stable_graph::StableGraph<node::Node, ()>,
+    adj_matrix: Option<Array2<u16>>,
+    nodes: Vec<node::Node>
 }
 
 impl network::Network for CtbnNetwork {
-    fn add_node(&mut self, mut n:  node::Node) -> Result<petgraph::graph::NodeIndex, network::NetworkError> {
+    fn initialize_adj_matrix(&mut self) {
+        self.adj_matrix = Some(Array2::<u16>::zeros((self.nodes.len(), self.nodes.len()).f()));
+
+    }
+
+    fn add_node(&mut self, mut n:  node::Node) -> Result<usize, network::NetworkError> {
         n.reset_params();
-        Ok(self.network.add_node(n))        
+        self.adj_matrix = Option::None;
+        self.nodes.push(n);
+        Ok(self.nodes.len() -1)        
     }
 
-    fn add_edge(&mut self, parent: &petgraph::stable_graph::NodeIndex, child: &petgraph::graph::NodeIndex) {
-        self.network.add_edge(parent.clone(), child.clone(), {});
-        let mut p = self.network.node_weight_mut(child.clone()).unwrap();
-        p.reset_params();
+    fn add_edge(&mut self, parent: usize, child: usize) {
+        if let None = self.adj_matrix {
+            self.initialize_adj_matrix();
+        }
+
+        if let Some(network) = &mut self.adj_matrix {
+            network[[parent, child]] = 1;
+            self.nodes[child].reset_params();
+        }
     }
 
-    fn get_node_indices(&self) -> petgraph::stable_graph::NodeIndices<node::Node>{
-        self.network.node_indices() 
+    fn get_node_indices(&self) -> std::ops::Range<usize>{
+        0..self.nodes.len()
     }
 
-    fn get_node(&self, node_idx: &petgraph::stable_graph::NodeIndex) -> &node::Node{
-        self.network.node_weight(node_idx.clone()).unwrap()
+    fn get_node(&self, node_idx: usize) -> &node::Node{
+        &self.nodes[node_idx]
     }
 
-    fn get_param_index_parents(&self, node: &petgraph::stable_graph::NodeIndex, u: &Vec<StateType>) -> usize{
-        self.network.neighbors_directed(node.clone(), Direction::Incoming).zip(u).fold((0, 1), |mut acc, x| {
-            let n = self.get_node(node);
-            acc.0 += n.state_to_index(&x.1) * acc.1;
-            acc.1 *= n.get_reserved_space_as_parent();
-            acc
 
+    fn get_param_index_network(&self, node: usize, current_state: &Vec<StateType>) -> usize{
+        self.adj_matrix.as_ref().unwrap().column(node).iter().enumerate().fold((0, 1), |mut acc, x| {
+            if x.1 > &0 {
+                acc.0 += self.nodes[x.0].state_to_index(&current_state[x.0]) * acc.1;
+                acc.1 *= self.nodes[x.0].get_reserved_space_as_parent();
+            }
+            acc
         }).0
     }
 
-
-    fn get_param_index_network(&self, node: &petgraph::stable_graph::NodeIndex, current_state: &Vec<StateType>) -> usize{
-        self.get_param_index_parents(node, &current_state.iter()
-                                     .zip(self.get_node_indices())
-                                     .filter_map(|x| {
-                                         match self.network.find_edge(x.1, node.clone()) {
-                                            Some(_) => Some(x.0.clone()),
-                                            None => None
-                                         }
-                                     }).collect()
-                                     )
+    fn get_parent_set(&self, node: usize) -> Vec<usize> {
+        self.adj_matrix.as_ref()
+            .unwrap()
+            .column(node)
+            .iter()
+            .enumerate()
+            .filter_map(|(idx, x)| {
+                if x > &0 {
+                    Some(idx)
+                } else {
+                    None
+                }
+            }).collect()
+    }
+    fn get_children_set(&self, node: usize) -> Vec<usize>{
+        self.adj_matrix.as_ref()
+            .unwrap()
+            .row(node)
+            .iter()
+            .enumerate()
+            .filter_map(|(idx, x)| {
+                if x > &0 {
+                    Some(idx)
+                } else {
+                    None
+                }
+            }).collect()
     }
 
 }
diff --git a/src/network.rs b/src/network.rs
index cd1f8a9..03d132e 100644
--- a/src/network.rs
+++ b/src/network.rs
@@ -1,6 +1,7 @@
-use petgraph::prelude::*; use crate::node;
 use thiserror::Error;
 use crate::params;
+use ndarray::prelude::*;
+use crate::node;
 
 #[derive(Error, Debug)]
 pub enum NetworkError {
@@ -9,10 +10,12 @@ pub enum NetworkError {
 }
 
 pub trait Network {
-    fn add_node(&mut self, n:  node::Node) -> Result<petgraph::graph::NodeIndex, NetworkError>;
-    fn add_edge(&mut self, parent: &petgraph::stable_graph::NodeIndex, child: &petgraph::graph::NodeIndex);
-    fn get_node_indices(&self) -> petgraph::stable_graph::NodeIndices<node::Node>;
-    fn get_node(&self, node_idx: &petgraph::stable_graph::NodeIndex) -> &node::Node;
-    fn get_param_index_parents(&self, node: &petgraph::stable_graph::NodeIndex, u: &Vec<params::StateType>) -> usize;
-    fn get_param_index_network(&self, node: &petgraph::stable_graph::NodeIndex, current_state: &Vec<params::StateType>) -> usize;
+    fn initialize_adj_matrix(&mut self);
+    fn add_node(&mut self, n:  node::Node) -> Result<usize, NetworkError>;
+    fn add_edge(&mut self, parent: usize, child: usize);
+    fn get_node_indices(&self) -> std::ops::Range<usize>;
+    fn get_node(&self, node_idx: usize) -> &node::Node;
+    fn get_param_index_network(&self, node: usize, current_state: &Vec<params::StateType>) -> usize;
+    fn get_parent_set(&self, node: usize) -> Vec<usize>;
+    fn get_children_set(&self, node: usize) -> Vec<usize>;
 }
diff --git a/src/node.rs b/src/node.rs
index 2707d69..8c922c8 100644
--- a/src/node.rs
+++ b/src/node.rs
@@ -1,4 +1,4 @@
-use std::collections::BTreeSet; use petgraph::prelude::*;
+use std::collections::BTreeSet;
 use crate::params::*;
 
 pub enum NodeType {
@@ -33,6 +33,28 @@ impl Node {
         }
     }
 
+    
+    pub fn get_random_residence_time(&self, state: usize, u:usize) -> Result<f64, ParamsError> {
+        match &self.params {
+            NodeType::DiscreteStatesContinousTime(params) => params.get_random_residence_time(state, u)
+        }
+    }
+
+
+    pub fn get_random_state_uniform(&self) -> StateType {
+        match &self.params {
+            NodeType::DiscreteStatesContinousTime(params) => params.get_random_state_uniform()
+        }
+    }
+
+
+    pub fn get_random_state(&self, state: usize, u:usize) -> Result<StateType, ParamsError>{
+        match &self.params {
+            NodeType::DiscreteStatesContinousTime(params) => params.get_random_state(state, u)
+        }
+    }
+
+
 }
 
 impl PartialEq for Node {
diff --git a/src/params.rs b/src/params.rs
index 2cd24db..f3793a3 100644
--- a/src/params.rs
+++ b/src/params.rs
@@ -1,6 +1,5 @@
 use ndarray::prelude::*;
 use std::collections::{HashMap, BTreeSet};
-use petgraph::prelude::*;
 use rand::Rng;
 use thiserror::Error;
 
diff --git a/src/tools.rs b/src/tools.rs
index 6258a19..048a77b 100644
--- a/src/tools.rs
+++ b/src/tools.rs
@@ -1,5 +1,4 @@
 use ndarray::prelude::*;
-use petgraph::prelude::*;
 use crate::network;
 use crate::node;
 use crate::params;
@@ -22,28 +21,54 @@ pub fn trajectory_generator(net: &Box<dyn network::Network>, n_trajectories: u64
 
     let node_idx: Vec<_> = net.get_node_indices().collect();
     for _ in 0..n_trajectories {
-        let t = 0.0;
+        let mut t = 0.0;
         let mut time: Vec<f64> = Vec::new();
         let mut events: Vec<Vec<params::StateType>> = Vec::new();
         let mut current_state: Vec<params::StateType> = node_idx.iter().map(|x| {
-            match net.get_node(&x).get_params() {
-                node::NodeType::DiscreteStatesContinousTime(params) => 
-                    params.get_random_state_uniform()
-}
+            net.get_node(*x).get_random_state_uniform()
         }).collect();
-        let next_transitions: Vec<Option<f64>> = (0..node_idx.len()).map(|_| Option::None).collect();
+        let mut next_transitions: Vec<Option<f64>> = (0..node_idx.len()).map(|_| Option::None).collect();
         events.push(current_state.clone());
         time.push(t.clone());
         while t < t_end {
-            next_transitions.iter_mut().zip(net.get_node_indices()).map(|x| {
-                if let None = x.0 {
-                    *(x.0) = Some(match net.get_node(&x.1).get_params(){
-                        node::NodeType::DiscreteStatesContinousTime(params) => 
-                            params.get_random_residence_time(x.1, net.get_param_index_network(&x.1, &current_state)).unwrap()
-                    });
-                }});
+            next_transitions.iter_mut().enumerate().map(|(idx, val)| {
+                if let None = val {
+                    *val = Some(net.get_node(idx)
+                                .get_random_residence_time(net.get_node(idx).state_to_index(&current_state[idx]), 
+                                                           net.get_param_index_network(idx, &current_state)).unwrap() + t);
+                }
+            });
+            let next_node_transition = next_transitions
+                .iter()
+                .enumerate()
+                .min_by(|x, y| 
+                        x.1.unwrap().partial_cmp(&y.1.unwrap()).unwrap())
+                .unwrap().0;
+            
+            if next_transitions[next_node_transition].unwrap() > t_end {
+                break
+            }
+            
+            t = next_transitions[next_node_transition].unwrap().clone();
+            time.push(t.clone());
+
+            current_state[next_node_transition] = net.get_node(next_node_transition)
+                                .get_random_state(
+                                    net.get_node(next_node_transition).
+                                    state_to_index(
+                                        &current_state[next_node_transition]),
+                                        net.get_param_index_network(next_node_transition, &current_state))
+                                .unwrap();
 
+            events.push(current_state.clone());
+            next_transitions[next_node_transition] = None;
             
+            for child in net.get_children_set(next_node_transition){
+                next_transitions[child] = None
+            }
+
+
+
         }