refact(jssp): extract delay_g computation to spearate function (#446)

## Description

This will allow for parameterization

examples/jssp/problem/fitness.rs

@@ -35,7 +35,7 @@ impl JsspFitness {
             indv.reset();
         }
 
-        // Resolving problem size. -2 because zero & sing dummy operations
+        // Resolving problem size. -2 because zero & sink dummy operations
         let n: usize = indv.operations.len() - 2;
 
         // TODO: This state is not hoisted, as we do not know the number of operations
@@ -58,13 +58,13 @@ impl JsspFitness {
         let mut t_g = 0;
 
         // Longest duration of a single opration
-        let max_dur = indv.operations.iter().map(|op| op.duration).max().unwrap();
+        let maxdur = indv.operations.iter().map(|op| op.duration).max().unwrap();
 
         let mut last_finish_time = 0;
         while self.scheduled.len() < n + 1 {
             // Calculate the delay. The formula is taken straight from the paper.
             // TODO: Parameterize this & conduct experiments
-            let mut delay = indv.chromosome[n + g - 1] * 1.5 * (max_dur as f64);
+            let mut delay = self.delay_for_g(indv, n, g, maxdur);
             self.update_delay_feasible_set(indv, &finish_times, delay, t_g);
 
             while !self.delay_feasibles.is_empty() {
@@ -95,7 +95,7 @@ impl JsspFitness {
                 let finish_time_j = finish_times
                     .iter()
                     .filter(|&&t| t != usize::MAX && t >= pred_j_finish)
-                    .filter(|&&t| indv.machines[op_j.machine].is_idle(t..=t + op_j_duration))
+                    .filter(|&&t| indv.machines[op_j_machine].is_idle(t..=t + op_j_duration))
                     .min()
                     .unwrap()
                     + op_j_duration;
@@ -120,7 +120,7 @@ impl JsspFitness {
                     break;
                 }
 
-                delay = indv.chromosome[n + g - 1] * 1.5 * (max_dur as f64);
+                delay = self.delay_for_g(indv, n, g, maxdur);
 
                 self.update_delay_feasible_set(indv, &finish_times, delay, t_g);
             }
@@ -136,6 +136,11 @@ impl JsspFitness {
         makespan
     }
 
+    #[inline(always)]
+    fn delay_for_g(&self, indv: &JsspIndividual, n: usize, g: usize, maxdur: usize) -> f64 {
+        indv.chromosome[n + g - 1] * 1.5 * (maxdur as f64)
+    }
+
     fn update_delay_feasible_set(
         &mut self,
         indv: &JsspIndividual,