chore: add debug symbols to release build & some comments (#439)

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## Description

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## Linked issues

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## Important implementation details

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Cargo.toml

@@ -65,3 +65,6 @@ required-features = ["ff"]
 [profile.dev]
 opt-level = 0
 debug = true
+
+[profile.release]
+debug = 1 # For profiling, should be disabled for production builds

examples/jssp/problem/individual.rs

@@ -289,6 +289,10 @@ impl JsspIndividual {
                 let op_j = &self.operations[j];
 
                 // Calculate the earliest finish time (in terms of precedence only)
+                // TODO: We do not need to look on all predecessors. The direct one is enough, as
+                // it could not be scheduled before all his preds were finished. The question is:
+                // is the order of predecessors guaranteed? Look for places that manipulate this
+                // field!
                 let pred_j_finish = op_j
                     .preds
                     .iter()