Track the simulation time, and configure the feature size

examples/coremem.rs

@@ -4,7 +4,7 @@ use coremem::consts;
 use std::{thread, time};
 
 fn main() {
-    let mut state = SimState::new(101, 101);
+    let mut state = SimState::new(101, 101, 1e-3 /* feature size */);
 
     for y in 70..100 {
         for x in 0..100 {

src/lib.rs

@@ -34,23 +34,35 @@ pub mod consts {
         pub fn MU0() -> R64 {
             super::MU0.into()
         }
+        pub fn HALF() -> R64 {
+            0.5.into()
+        }
     }
 }
 
 #[derive(Default)]
 pub struct SimState {
     cells: Array2<Cell<GenericMaterial>>,
+    feature_size: R64,
+    step_no: u64,
 }
 
 impl SimState {
-    pub fn new(width: usize, height: usize) -> Self {
+    pub fn new(width: usize, height: usize, feature_size: f64) -> Self {
         Self {
             cells: Array2::default((height, width)),
+            feature_size: feature_size.into(),
+            ..Default::default()
         }
     }
+    
+    pub fn time(&self) -> f64 {
+        (self.timestep() * self.step_no as f64).into()
+    }
 
     pub fn step(&mut self) {
-        // feature size: 1mm.
+        use consts::real::*;
+        let half_time_step = HALF() * self.timestep();
         let half_time_step = 0.0005 / consts::C;
         let mut working_cells = Array2::default((self.height(), self.width()));
         // first advance all the magnetic fields
@@ -74,6 +86,7 @@ impl SimState {
             }
         }
         std::mem::swap(&mut working_cells, &mut self.cells);
+        self.step_no += 1;
     }
 
     pub fn impulse_ex(&mut self, x: usize, y: usize, ex: f64) {
@@ -98,6 +111,11 @@ impl SimState {
     pub fn get_mut(&mut self, x: usize, y: usize) -> &mut Cell<GenericMaterial> {
         &mut self.cells[[y, x]]
     }
+
+
+    fn timestep(&self) -> R64 {
+        self.feature_size / consts::real::C()
+    }
 }
 
 /// Conceptually, one cell looks like this:

src/render.rs

@@ -60,6 +60,6 @@ impl ColorTermRenderer {
             }
             write!(&mut buf, "\n");
         }
-        println!("{}", buf);
+        println!("{}\ntime: {:.3e}", buf, state.time());
     }
 }