Added parameters

readme.md

@@ -39,20 +39,30 @@ use differential_equations::controller::PIController;
 use differential_equations::callback::stop;
 use differential_equations::problem::*;
 
-// Define the system
+// Define the system (parameters, derivative, and initial state)
-fn derivative(_t: f64, y: Vector3<f64>) -> Vector3<f64> { y }
+type Params = (f64, bool);
+let params = (34.0, true);
+
+fn derivative(t: f64, y: Vector3<f64>, p: &Params) -> Vector3<f64> {
+  if p.1 { -y } else { y * t }
+}
+
 let y0 = Vector3::new(1.0, 1.0, 1.0);
 
-let ode = ODE::new(&derivative, 0.0, 10.0, y0);
+// Set up the problem (ODE, Integrator, Controller, and Callbacks)
+let ode = ODE::new(&derivative, 0.0, 10.0, y0, params);
 let dp45 = DormandPrince45::new(1e-12_f64, 1e-5_f64);
 let controller = PIController::default();
 
 let value_too_high = Callback {
-    event: &|_: f64, y: SVector<f64,3>| { 10.0 - y[0] },
+  event: &|_: f64, y: Vector3<f64>, _: &Params| { 10.0 - y[0] },
     effect: &stop,
 };
 
+// Solve the problem
 let mut problem = Problem::new(ode, dp45, controller).with_callback(value_too_high);
 let solution = problem.solve();
+
+// Can interpolate solutions to whatever you want
 let interpolated_answer = solution.interpolate(8.2);
 ```

src/callback.rs

@@ -1,23 +1,22 @@
 use nalgebra::SVector;
+
 use super::ode::ODE;
 
 /// A function that takes in a time and a state and outputs a single float value
 ///
 /// The integration solver will check this function for zero crossings
 #[derive(Clone, Copy)]
-pub struct Callback<'a, const D: usize> {
+pub struct Callback<'a, const D: usize, P> {
     /// The function to check for zero crossings
-    pub event: &'a dyn Fn(f64, SVector<f64,D>) -> f64,
+    pub event: &'a dyn Fn(f64, SVector<f64,D>, &P) -> f64,
 
     /// The function to change the ODE
-    pub effect: &'a dyn Fn(ODE<D>) -> ODE<D>,
+    pub effect: &'a dyn Fn(&mut ODE<D,P>) -> (),
 }
 
 /// A convenience function for stopping the integration
-pub fn stop<const D: usize>(ode: ODE<D>) -> ODE<D> {
+pub fn stop<'a, const D: usize, P>(ode: &mut ODE<D,P>) -> () {
-    let mut new_ode = ode.clone();
+    ode.t_end = ode.t;
-    new_ode.t_end = new_ode.t;
-    new_ode
 }
 
 #[cfg(test)]
@@ -26,8 +25,9 @@ mod tests {
 
     #[test]
     fn test_basic_callbacks() {
+        type Params = ();
         let _value_too_high = Callback {
-            event: &|_: f64, y: SVector<f64,3>| { 10.0 - y[0] },
+            event: &|_: f64, y: SVector<f64,3>, _p: &Params| { 10.0 - y[0] },
             effect: &stop,
         };
     }

src/integrator/dormand_prince.rs

@@ -95,13 +95,13 @@ where
     const ADAPTIVE: bool = true;
     const DENSE: bool = true;
 
-    fn step(&self, ode: &ODE<D>, h: f64) -> (SVector<f64,D>, Option<f64>, Option<Vec<SVector<f64, D>>>) {
+    fn step<P>(&self, ode: &ODE<D,P>, h: f64) -> (SVector<f64,D>, Option<f64>, Option<Vec<SVector<f64, D>>>) {
         let mut k: Vec<SVector::<f64,D>> = vec![SVector::<f64,D>::zeros(); Self::STAGES];
         let mut next_y = ode.y.clone();
         let mut err = SVector::<f64, D>::zeros();
         let mut rcont5 = SVector::<f64, D>::zeros();
         // Do the first of the summations
-        k[0] = (ode.f)(ode.t, ode.y);
+        k[0] = (ode.f)(ode.t, ode.y, &ode.params);
         next_y += k[0] * Self::B[0] * h;
         err += k[0] * (Self::B[0] - Self::B[Self::STAGES]) * h;
         let rcont1 = ode.y;
@@ -113,7 +113,7 @@ where
             for j in 0..i {
                 y_term += k[j] * Self::A[( i * (i - 1) ) / 2 + j];
             }
-            k[i] = (ode.f)(ode.t + Self::C[i] * h, ode.y + y_term * h);
+            k[i] = (ode.f)(ode.t + Self::C[i] * h, ode.y + y_term * h, &ode.params);
 
             // Use that and bis to calculate the y and error terms
             next_y += k[i] * h * Self::B[i];

src/integrator/mod.rs

@@ -13,7 +13,7 @@ pub trait Integrator<const D: usize> {
     const DENSE: bool;
     /// Returns a new y value, then possibly an error value, and possibly a dense output
     /// coefficient set
-    fn step(&self, ode: &ODE<D>, h: f64) -> (SVector<f64,D>, Option<f64>, Option<Vec<SVector<f64, D>>>);
+    fn step<P>(&self, ode: &ODE<D,P>, h: f64) -> (SVector<f64,D>, Option<f64>, Option<Vec<SVector<f64, D>>>);
     fn interpolate(&self, t_start: f64, t_end: f64, dense: &Vec<SVector<f64,D>>, t: f64) -> SVector<f64,D>;
 }
 
@@ -28,10 +28,11 @@ mod tests {
 
     #[test]
     fn test_dopri() {
-        fn derivative(_t: f64, y: Vector3<f64>) -> Vector3<f64> { y }
+        type Params = ();
+        fn derivative(_t: f64, y: Vector3<f64>, _p: &Params) -> Vector3<f64> { y }
 
         let y0 = Vector3::new(1.0, 1.0, 1.0);
-        let mut ode = ODE::new(&derivative, 0.0, 4.0, y0);
+        let mut ode = ODE::new(&derivative, 0.0, 4.0, y0, ());
 
         let dp45 = DormandPrince45::new(1e-12_f64, 1e-4_f64);
 

src/lib.rs

@@ -9,24 +9,57 @@ pub mod problem;
 
 #[cfg(test)]
 mod tests {
-    use nalgebra::Vector6;
+    use nalgebra::{Vector3, Vector6};
     use approx::assert_relative_eq;
     use crate::integrator::dormand_prince::DormandPrince45;
     use crate::controller::PIController;
+    use crate::callback::{Callback, stop};
     use crate::ode::ODE;
     use crate::problem::Problem;
     use std::f64::consts::PI;
 
     #[test]
-    fn test_orbit() {
+    fn test_readme() {
+        // Define the system (parameters, derivative, and initial state)
+        type Params = (f64, bool);
+        let params = (34.0, true);
 
+        fn derivative(t: f64, y: Vector3<f64>, p: &Params) -> Vector3<f64> {
+          if p.1 { -y } else { y * t }
+        }
+
+        let y0 = Vector3::new(1.0, 1.0, 1.0);
+
+        // Set up the problem (ODE, Integrator, Controller, and Callbacks)
+        let ode = ODE::new(&derivative, 0.0, 10.0, y0, params);
+        let dp45 = DormandPrince45::new(1e-12_f64, 1e-5_f64);
+        let controller = PIController::default();
+
+        let value_too_high = Callback {
+            event: &|_: f64, y: Vector3<f64>, _: &Params| { 10.0 - y[0] },
+            effect: &stop,
+        };
+
+        // Solve the problem
+        let mut problem = Problem::new(ode, dp45, controller).with_callback(value_too_high);
+        let solution = problem.solve();
+
+        // Can interpolate solutions to whatever you want
+        let _interpolated_answer = solution.interpolate(8.2);
+    }
+
+    #[test]
+    fn test_orbit() {
         // Calculate one period
         let a = 6.7781363e6_f64;
-        let period = 2.0 * PI * (a.powi(3)/3.98600441500000e14).sqrt();
+        let mu = 3.98600441500000e14;
+        let period = 2.0 * PI * (a.powi(3)/mu).sqrt();
 
         // Set up the system
-        fn derivative(_t: f64, state: Vector6<f64>) -> Vector6<f64> {
+        type Params = (f64,);
-            let acc = -(3.98600441500000e14 * state.fixed_rows::<3>(0)) / (state.fixed_rows::<3>(0).norm().powi(3));
+        let params = (mu,);
+        fn derivative(_t: f64, state: Vector6<f64>, p: &Params) -> Vector6<f64> {
+            let acc = -(p.0 * state.fixed_rows::<3>(0)) / (state.fixed_rows::<3>(0).norm().powi(3));
             Vector6::new(state[3], state[4], state[5], acc[0], acc[1], acc[2])
         }
         let y0 = Vector6::new(
@@ -39,7 +72,7 @@ mod tests {
         );
 
         // Integrate
-        let ode = ODE::new(&derivative, 0.0, 10.0*period, y0);
+        let ode = ODE::new(&derivative, 0.0, 10.0*period, y0, params);
         let dp45 = DormandPrince45::new(1e-12_f64, 1e-12_f64);
         let controller = PIController::new(0.37, 0.04, 10.0, 0.2, 1000.0, 0.9, 0.01);
 

src/ode.rs

@@ -3,22 +3,30 @@ use nalgebra::SVector;
 /// The basic ODE object that will be passed around. The type (T) and the size (D) will be
 /// determined upon creation of the object
 #[derive(Clone, Copy)]
-pub struct ODE<'a, const D: usize> {
+pub struct ODE<'a, const D: usize, P> {
-    pub f: &'a dyn Fn(f64, SVector<f64,D>) -> SVector<f64,D>,
+    pub f: &'a dyn Fn(f64, SVector<f64,D>, &P) -> SVector<f64,D>,
     pub y: SVector<f64,D>,
     pub t: f64,
+    pub params: P,
     pub t0: f64,
     pub t_end: f64,
     pub h: f64,
     pub finished: bool,
 }
 
-impl<'a, const D: usize> ODE<'a,D> {
+impl<'a, const D: usize, P> ODE<'a,D, P> {
-    pub fn new(f: &'a (dyn Fn(f64, SVector<f64,D>) -> SVector<f64,D>), t0: f64, t_end: f64, y0: SVector<f64,D>) -> Self {
+    pub fn new(
+        f: &'a (dyn Fn(f64, SVector<f64,D>, &P) -> SVector<f64,D>),
+        t0: f64,
+        t_end: f64,
+        y0: SVector<f64,D>,
+        params: P,
+    ) -> Self {
         Self {
             f: f,
             y: y0,
             t: t0,
+            params: params,
             t0: t0,
             t_end: t_end,
             h: 0.001,
@@ -35,12 +43,32 @@ mod tests {
 
     #[test]
     fn test_ode_creation() {
-        fn derivative(_t: f64, y: Vector3<f64>) -> Vector3<f64> { -y }
+        type Params = ();
+        fn derivative(_t: f64, y: Vector3<f64>, _p: &Params) -> Vector3<f64> { -y }
 
         let y0 = Vector3::new(1.0, 0.0, 0.0);
-        let ode = ODE::new(&derivative, 0.0, 10.0, y0);
+        let ode = ODE::new(&derivative, 0.0, 10.0, y0, ());
 
-        assert!((ode.f)(0.0, y0) == Vector3::new(-1.0, 0.0, 0.0));
+        assert!((ode.f)(0.0, y0, &()) == Vector3::new(-1.0, 0.0, 0.0));
+        assert!(ode.y == Vector3::new(1.0, 0.0, 0.0));
+        assert!(ode.t == 0.0);
+        assert!(!ode.finished);
+        assert!(ode.t_end == 10.0);
+    }
+
+    #[test]
+    fn test_ode_with_params() {
+        type Params = (f64, bool);
+        let params = (34.0, true);
+
+        fn derivative(t: f64, y: Vector3<f64>, p: &Params) -> Vector3<f64> {
+          if p.1 { -y } else { y * t }
+        }
+
+        let y0 = Vector3::new(1.0, 0.0, 0.0);
+        let ode = ODE::new(&derivative, 0.0, 10.0, y0, params);
+
+        assert!((ode.f)(0.0, y0, &params) == Vector3::new(-1.0, 0.0, 0.0));
         assert!(ode.y == Vector3::new(1.0, 0.0, 0.0));
         assert!(ode.t == 0.0);
         assert!(!ode.finished);

src/problem.rs

@@ -7,21 +7,21 @@ use super::integrator::Integrator;
 use super::callback::Callback;
 
 #[derive(Clone)]
-pub struct Problem<'a, const D: usize, S>
+pub struct Problem<'a, const D: usize, S, P>
 where
     S: Integrator<D>,
 {
-    ode: ODE<'a, D>,
+    ode: ODE<'a, D, P>,
     integrator: S,
     controller: PIController,
-    callbacks: Vec<Callback<'a, D>>,
+    callbacks: Vec<Callback<'a, D, P>>,
 }
 
-impl<'a, const D: usize, S> Problem<'a,D,S>
+impl<'a, const D: usize, S, P> Problem<'a,D,S,P>
 where
     S: Integrator<D> + Copy,
 {
-    pub fn new(ode: ODE<'a,D>, integrator: S, controller: PIController) -> Self {
+    pub fn new(ode: ODE<'a,D,P>, integrator: S, controller: PIController) -> Self {
         Problem {
             ode: ode,
             integrator: integrator,
@@ -55,17 +55,17 @@ where
             if self.callbacks.len() > 0 {
                 // Check for events occurring
                 for callback in &self.callbacks {
-                    println!("{}", (callback.event)(self.ode.t, self.ode.y) * (callback.event)(self.ode.t + step, new_y));
+                    println!("{}", (callback.event)(self.ode.t, self.ode.y, &self.ode.params) * (callback.event)(self.ode.t + step, new_y, &self.ode.params));
-                    if (callback.event)(self.ode.t, self.ode.y) * (callback.event)(self.ode.t + step, new_y) < 0.0 {
+                    if (callback.event)(self.ode.t, self.ode.y, &self.ode.params) * (callback.event)(self.ode.t + step, new_y, &self.ode.params) < 0.0 {
                         // If the event crossed zero, then find the root
                         let f = |test_t| {
                             let test_y = self.integrator.step(&self.ode, test_t).0;
-                            (callback.event)(self.ode.t + test_t, test_y)
+                            (callback.event)(self.ode.t + test_t, test_y, &self.ode.params)
                         };
                         let root = find_root_regula_falsi(0.0, step, &f, &mut 1e-12).unwrap();
                         step = root;
                         (new_y, _, dense_option) = self.integrator.step(&self.ode, step);
-                        self.ode = (callback.effect)(self.ode);
+                        (callback.effect)(&mut self.ode);
                     }
                 }
             }
@@ -84,7 +84,7 @@ where
         }
     }
 
-    pub fn with_callback(mut self, callback: Callback<'a, D>) -> Self {
+    pub fn with_callback(mut self, callback: Callback<'a, D, P>) -> Self {
         self.callbacks.push(callback);
         Self {
             ode: self.ode,
@@ -140,10 +140,11 @@ mod tests {
 
     #[test]
     fn test_problem() {
-        fn derivative(_t: f64, y: Vector3<f64>) -> Vector3<f64> { y }
+        type Params = ();
+        fn derivative(_t: f64, y: Vector3<f64>, _p: &Params) -> Vector3<f64> { y }
         let y0 = Vector3::new(1.0, 1.0, 1.0);
 
-        let ode = ODE::new(&derivative, 0.0, 1.0, y0);
+        let ode = ODE::new(&derivative, 0.0, 1.0, y0, ());
         let dp45 = DormandPrince45::new(1e-12_f64, 1e-5_f64);
         let controller = PIController::default();
 
@@ -157,15 +158,16 @@ mod tests {
 
     #[test]
     fn test_with_callback() {
-        fn derivative(_t: f64, y: Vector3<f64>) -> Vector3<f64> { y }
+        type Params = ();
+        fn derivative(_t: f64, y: Vector3<f64>, _p: &Params) -> Vector3<f64> { y }
         let y0 = Vector3::new(1.0, 1.0, 1.0);
 
-        let ode = ODE::new(&derivative, 0.0, 5.0, y0);
+        let ode = ODE::new(&derivative, 0.0, 10.0, y0, ());
         let dp45 = DormandPrince45::new(1e-12_f64, 1e-5_f64);
         let controller = PIController::default();
 
         let value_too_high = Callback {
-            event: &|_: f64, y: SVector<f64,3>| { 10.0 - y[0] },
+            event: &|_: f64, y: SVector<f64,3>, _: &Params| { 10.0 - y[0] },
             effect: &stop,
         };
 
@@ -178,10 +180,11 @@ mod tests {
 
     #[test]
     fn test_with_interpolation() {
-        fn derivative(_t: f64, y: Vector3<f64>) -> Vector3<f64> { y }
+        type Params = ();
+        fn derivative(_t: f64, y: Vector3<f64>, _p: &Params) -> Vector3<f64> { y }
         let y0 = Vector3::new(1.0, 1.0, 1.0);
 
-        let ode = ODE::new(&derivative, 0.0, 10.0, y0);
+        let ode = ODE::new(&derivative, 0.0, 10.0, y0, ());
         let dp45 = DormandPrince45::new(1e-12_f64, 1e-6_f64);
         let controller = PIController::default();