Handle LCOX errors gracefully

src/finance.rs

@@ -74,12 +74,14 @@ pub fn profitability_index(
 }
 
 /// Calculates annual LCOX based on capacity and activity.
+///
+/// If the total activity is zero, then it returns `None`, otherwise `Some` LCOX value.
 pub fn lcox(
     capacity: Capacity,
     annual_fixed_cost: MoneyPerCapacity,
     activity: &IndexMap<TimeSliceID, Activity>,
     activity_costs: &IndexMap<TimeSliceID, MoneyPerActivity>,
-) -> MoneyPerActivity {
+) -> Option<MoneyPerActivity> {
     // Calculate the annualised fixed costs
     let annualised_fixed_cost = annual_fixed_cost * capacity;
 
@@ -92,7 +94,8 @@ pub fn lcox(
         total_activity_costs += activity_cost * *activity;
     }
 
-    (annualised_fixed_cost + total_activity_costs) / total_activity
+    (total_activity > Activity(0.0))
+        .then(|| (annualised_fixed_cost + total_activity_costs) / total_activity)
 }
 
 #[cfg(test)]
@@ -223,20 +226,26 @@ mod tests {
         100.0, 50.0,
         vec![("winter", "day", 10.0), ("summer", "night", 20.0)],
         vec![("winter", "day", 5.0), ("summer", "night", 3.0)],
-        170.33333333333334 // (100*50 + 10*5 + 20*3) / (10+20) = 5110/30
+        Some(170.33333333333334) // (100*50 + 10*5 + 20*3) / (10+20) = 5110/30
     )]
     #[case(
         50.0, 100.0,
         vec![("winter", "day", 25.0)],
         vec![("winter", "day", 0.0)],
-        200.0 // (50*100 + 25*0) / 25 = 5000/25
+        Some(200.0) // (50*100 + 25*0) / 25 = 5000/25
+    )]
+    #[case(
+        50.0, 100.0,
+        vec![("winter", "day", 0.0)],
+        vec![("winter", "day", 0.0)],
+        None // (50*0 + 25*0) / 0 = not feasible
     )]
     fn lcox_works(
         #[case] capacity: f64,
         #[case] annual_fixed_cost: f64,
         #[case] activity_data: Vec<(&str, &str, f64)>,
         #[case] cost_data: Vec<(&str, &str, f64)>,
-        #[case] expected: f64,
+        #[case] expected: Option<f64>,
     ) {
         let activity = activity_data
             .into_iter()
@@ -271,7 +280,7 @@ mod tests {
             &activity_costs,
         );
 
-        let expected = MoneyPerActivity(expected);
-        assert_approx_eq!(MoneyPerActivity, result, expected);
+        let expected = expected.map(MoneyPerActivity);
+        assert_approx_eq!(Option<MoneyPerActivity>, result, expected);
     }
 }

src/fixture.rs

@@ -382,20 +382,18 @@ pub fn time_slice_info2() -> TimeSliceInfo {
 pub fn appraisal_output(asset: Asset, time_slice: TimeSliceID) -> AppraisalOutput {
     let activity_coefficients = indexmap! { time_slice.clone() => MoneyPerActivity(0.5) };
     let activity = indexmap! { time_slice.clone() => Activity(10.0) };
-    let demand = indexmap! { time_slice.clone() => Flow(100.0) };
     let unmet_demand = indexmap! { time_slice.clone() => Flow(5.0) };
     AppraisalOutput {
         asset: AssetRef::from(asset),
         capacity: AssetCapacity::Continuous(Capacity(42.0)),
-        coefficients: ObjectiveCoefficients {
+        coefficients: Rc::new(ObjectiveCoefficients {
             capacity_coefficient: MoneyPerCapacity(2.14),
             activity_coefficients,
             unmet_demand_coefficient: MoneyPerFlow(10000.0),
-        },
+        }),
         activity,
-        demand,
         unmet_demand,
-        metric: Box::new(LCOXMetric::new(MoneyPerActivity(4.14))),
+        metric: Some(Box::new(LCOXMetric::new(MoneyPerActivity(4.14)))),
     }
 }
 

src/output.rs

@@ -220,7 +220,7 @@ struct AppraisalResultsRow {
     region_id: RegionID,
     capacity: Capacity,
     capacity_coefficient: MoneyPerCapacity,
-    metric: f64,
+    metric: Option<f64>,
 }
 
 /// Represents the appraisal results in a row of the appraisal results CSV file
@@ -453,7 +453,7 @@ impl DebugDataWriter {
                 region_id: result.asset.region_id().clone(),
                 capacity: result.capacity.total_capacity(),
                 capacity_coefficient: result.coefficients.capacity_coefficient,
-                metric: result.metric.value(),
+                metric: result.metric.as_ref().map(|m| m.value()),
             };
             self.appraisal_results_writer.serialize(row)?;
         }
@@ -467,11 +467,12 @@ impl DebugDataWriter {
         milestone_year: u32,
         run_description: &str,
         appraisal_results: &[AppraisalOutput],
+        demand: &IndexMap<TimeSliceID, Flow>,
     ) -> Result<()> {
         for result in appraisal_results {
             for (time_slice, activity) in &result.activity {
                 let activity_coefficient = result.coefficients.activity_coefficients[time_slice];
-                let demand = result.demand[time_slice];
+                let demand = demand[time_slice];
                 let unmet_demand = result.unmet_demand[time_slice];
                 let row = AppraisalResultsTimeSliceRow {
                     milestone_year,
@@ -564,13 +565,15 @@ impl DataWriter {
         milestone_year: u32,
         run_description: &str,
         appraisal_results: &[AppraisalOutput],
+        demand: &IndexMap<TimeSliceID, Flow>,
     ) -> Result<()> {
         if let Some(wtr) = &mut self.debug_writer {
             wtr.write_appraisal_results(milestone_year, run_description, appraisal_results)?;
             wtr.write_appraisal_time_slice_results(
                 milestone_year,
                 run_description,
                 appraisal_results,
+                demand,
             )?;
         }
 
@@ -986,7 +989,7 @@ mod tests {
             region_id: asset.region_id().clone(),
             capacity: Capacity(42.0),
             capacity_coefficient: MoneyPerCapacity(2.14),
-            metric: 4.14,
+            metric: Some(4.14),
         };
         let records: Vec<AppraisalResultsRow> =
             csv::Reader::from_path(dir.path().join(APPRAISAL_RESULTS_FILE_NAME))
@@ -1006,6 +1009,7 @@ mod tests {
         let milestone_year = 2020;
         let run_description = "test_run".to_string();
         let dir = tempdir().unwrap();
+        let demand = indexmap! {time_slice.clone() => Flow(100.0) };
 
         // Write appraisal time slice results
         {
@@ -1015,6 +1019,7 @@ mod tests {
                     milestone_year,
                     &run_description,
                     &[appraisal_output],
+                    &demand,
                 )
                 .unwrap();
             writer.flush().unwrap();

src/simulation/investment.rs

@@ -796,6 +796,7 @@ fn select_best_assets(
             year,
             &format!("{} {} round {}", &commodity.id, &agent.id, round),
             &outputs_for_opts,
+            &demand,
         )?;
 
         sort_appraisal_outputs_by_investment_priority(&mut outputs_for_opts);