fix: Fix handling of zero loss in LossLink and WTW nodes.

When a constant zero loss is provided to LossLink or WTW nodes then no relationship is created on the internal aggregated node. This left the added Output node unconstrained. This fix ensures that the Output node is separately constrained to zero max_flow when there is zero loss.
pywr · Oct 8, 2024 · e779ff5 · e779ff5
1 parent aa56a1f
commit e779ff5
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Showing 6 changed files with 351 additions and 5 deletions.
diff --git a/pywr-schema/src/nodes/loss_link.rs b/pywr-schema/src/nodes/loss_link.rs
@@ -26,6 +26,8 @@ pub enum LossFactor {
 
 #[cfg(feature = "core")]
 impl LossFactor {
+    /// Load the loss factor and return a corresponding [`Relationship`] if the loss factor is
+    /// not a constant zero. If a zero is loaded, then `None` is returned.
     pub fn load(
         &self,
         network: &mut pywr_core::network::Network,
@@ -34,7 +36,7 @@ impl LossFactor {
         match self {
             LossFactor::Gross { factor } => {
                 let lf = factor.load(network, args)?;
-                // Handle the case where we a given a zero loss factor
+                // Handle the case where we are given a zero loss factor
                 // The aggregated node does not support zero loss factors so filter them here.
                 if lf.is_constant_zero() {
                     return Ok(None);
@@ -173,6 +175,11 @@ impl LossLinkNode {
 
         if let Some(loss_factor) = &self.loss_factor {
             let factors = loss_factor.load(network, args)?;
+
+            if factors.is_none() {
+                // Loaded a constant zero factor; ensure that the loss node has zero flow
+                network.set_node_max_flow(self.meta.name.as_str(), Self::loss_sub_name(), Some(0.0.into()))?;
+            }
             network.set_aggregated_node_relationship(self.meta.name.as_str(), Self::agg_sub_name(), factors)?;
         }
 
@@ -289,7 +296,7 @@ mod tests {
     }
 
     #[test]
-    fn test_model_schema() {
+    fn test_loss_link1_schema() {
         let data = loss_link1_str();
         let schema: PywrModel = serde_json::from_str(data).unwrap();
 
@@ -299,7 +306,7 @@ mod tests {
 
     #[test]
     #[cfg(feature = "core")]
-    fn test_model_run() {
+    fn test_loss_link1_run() {
         let data = loss_link1_str();
         let schema: PywrModel = serde_json::from_str(data).unwrap();
         let temp_dir = TempDir::new().unwrap();
@@ -314,4 +321,40 @@ mod tests {
         // Test all solvers
         run_all_solvers(&model, &[], &expected_outputs);
     }
+
+    fn loss_link2_str() -> &'static str {
+        include_str!("../test_models/loss_link2.json")
+    }
+
+    #[cfg(feature = "core")]
+    fn loss_link2_outputs_str() -> &'static str {
+        include_str!("../test_models/loss_link2-expected.csv")
+    }
+
+    #[test]
+    fn test_loss_link2_schema() {
+        let data = loss_link2_str();
+        let schema: PywrModel = serde_json::from_str(data).unwrap();
+
+        assert_eq!(schema.network.nodes.len(), 4);
+        assert_eq!(schema.network.edges.len(), 3);
+    }
+
+    #[test]
+    #[cfg(feature = "core")]
+    fn test_loss_link2_run() {
+        let data = loss_link2_str();
+        let schema: PywrModel = serde_json::from_str(data).unwrap();
+        let temp_dir = TempDir::new().unwrap();
+
+        let model = schema.build_model(None, Some(temp_dir.path())).unwrap();
+        // After model run there should be an output file.
+        let expected_outputs = [ExpectedOutputs::new(
+            temp_dir.path().join("loss_link2.csv"),
+            loss_link2_outputs_str(),
+        )];
+
+        // Test all solvers
+        run_all_solvers(&model, &[], &expected_outputs);
+    }
 }
diff --git a/pywr-schema/src/nodes/water_treatment_works.rs b/pywr-schema/src/nodes/water_treatment_works.rs
@@ -181,6 +181,10 @@ impl WaterTreatmentWorks {
 
         if let Some(loss_factor) = &self.loss_factor {
             let factors = loss_factor.load(network, args)?;
+            if factors.is_none() {
+                // Loaded a constant zero factor; ensure that the loss node has zero flow
+                network.set_node_max_flow(self.meta.name.as_str(), Self::loss_sub_name(), Some(0.0.into()))?;
+            }
             network.set_aggregated_node_relationship(self.meta.name.as_str(), Self::agg_sub_name(), factors)?;
         }
 
@@ -255,7 +259,7 @@ mod tests {
     }
 
     #[test]
-    fn test_model_schema() {
+    fn test_wtw1_schema() {
         let data = wtw1_str();
         let schema: PywrModel = serde_json::from_str(data).unwrap();
 
@@ -265,7 +269,7 @@ mod tests {
 
     #[test]
     #[cfg(feature = "core")]
-    fn test_model_run() {
+    fn test_wtw1_run() {
         let data = wtw1_str();
         let schema: PywrModel = serde_json::from_str(data).unwrap();
         let temp_dir = TempDir::new().unwrap();
@@ -285,4 +289,45 @@ mod tests {
         // Test all solvers
         run_all_solvers(&model, &[], &expected_outputs);
     }
+
+    fn wtw2_str() -> &'static str {
+        include_str!("../test_models/wtw2.json")
+    }
+
+    #[cfg(feature = "core")]
+    fn wtw2_outputs_str() -> &'static str {
+        include_str!("../test_models/wtw2-expected.csv")
+    }
+
+    #[test]
+    fn test_wtw2_schema() {
+        let data = wtw2_str();
+        let schema: PywrModel = serde_json::from_str(data).unwrap();
+
+        assert_eq!(schema.network.nodes.len(), 4);
+        assert_eq!(schema.network.edges.len(), 3);
+    }
+
+    #[test]
+    #[cfg(feature = "core")]
+    fn test_wtw2_run() {
+        let data = wtw2_str();
+        let schema: PywrModel = serde_json::from_str(data).unwrap();
+        let temp_dir = TempDir::new().unwrap();
+
+        let mut model = schema.build_model(None, Some(temp_dir.path())).unwrap();
+
+        let network = model.network_mut();
+        assert_eq!(network.nodes().len(), 7);
+        assert_eq!(network.edges().len(), 7);
+
+        // After model run there should be an output file.
+        let expected_outputs = [ExpectedOutputs::new(
+            temp_dir.path().join("wtw2.csv"),
+            wtw2_outputs_str(),
+        )];
+
+        // Test all solvers
+        run_all_solvers(&model, &[], &expected_outputs);
+    }
 }
diff --git a/pywr-schema/src/test_models/loss_link2-expected.csv b/pywr-schema/src/test_models/loss_link2-expected.csv
@@ -0,0 +1,13 @@
+time_start,time_end,scenario_index,metric_set,name,attribute,value
+2015-01-01T00:00:00,2015-01-02T00:00:00,0,nodes,loss1,Inflow,10.0
+2015-01-01T00:00:00,2015-01-02T00:00:00,0,nodes,loss1,Outflow,10.0
+2015-01-01T00:00:00,2015-01-02T00:00:00,0,nodes,loss1,Loss,0.0
+2015-01-01T00:00:00,2015-01-02T00:00:00,0,nodes,spill1,Inflow,5.0
+2015-01-02T00:00:00,2015-01-03T00:00:00,0,nodes,loss1,Inflow,10.0
+2015-01-02T00:00:00,2015-01-03T00:00:00,0,nodes,loss1,Outflow,10.0
+2015-01-02T00:00:00,2015-01-03T00:00:00,0,nodes,loss1,Loss,0.0
+2015-01-02T00:00:00,2015-01-03T00:00:00,0,nodes,spill1,Inflow,5.0
+2015-01-03T00:00:00,2015-01-04T00:00:00,0,nodes,loss1,Inflow,10.0
+2015-01-03T00:00:00,2015-01-04T00:00:00,0,nodes,loss1,Outflow,10.0
+2015-01-03T00:00:00,2015-01-04T00:00:00,0,nodes,loss1,Loss,0.0
+2015-01-03T00:00:00,2015-01-04T00:00:00,0,nodes,spill1,Inflow,5.0
diff --git a/pywr-schema/src/test_models/loss_link2.json b/pywr-schema/src/test_models/loss_link2.json
@@ -0,0 +1,116 @@
+{
+  "metadata": {
+    "title": "Loss Link Test 1",
+    "description": "Test LossLink with zero loss",
+    "minimum_version": "0.1"
+  },
+  "timestepper": {
+    "start": "2015-01-01",
+    "end": "2015-01-03",
+    "timestep": 1
+  },
+  "network": {
+    "nodes": [
+      {
+        "meta": {
+          "name": "input1"
+        },
+        "type": "Catchment",
+        "flow": {
+          "type": "Constant",
+          "value": 15.0
+        }
+      },
+      {
+        "meta": {
+          "name": "loss1"
+        },
+        "type": "LossLink",
+        "loss_factor": {
+          "type": "Net",
+          "factor": {
+            "type": "Constant",
+            "value": 0.0
+          }
+        }
+      },
+      {
+        "meta": {
+          "name": "demand1"
+        },
+        "type": "Output",
+        "max_flow": {
+          "type": "Constant",
+          "value": 10.0
+        },
+        "cost": {
+          "type": "Constant",
+          "value": -10
+        }
+      },
+      {
+        "meta": {
+          "name": "spill1"
+        },
+        "type": "Output",
+        "cost": {
+          "type": "Constant",
+          "value": 10
+        }
+      }
+    ],
+    "edges": [
+      {
+        "from_node": "input1",
+        "to_node": "loss1"
+      },
+      {
+        "from_node": "loss1",
+        "to_node": "demand1"
+      },
+      {
+        "from_node": "input1",
+        "to_node": "spill1"
+      }
+    ],
+    "metric_sets": [
+      {
+        "name": "nodes",
+        "metrics": [
+          {
+            "type": "Node",
+            "name": "loss1",
+            "attribute": "Inflow"
+          },
+          {
+            "type": "Node",
+            "name": "loss1",
+            "attribute": "Outflow"
+          },
+          {
+            "type": "Node",
+            "name": "loss1",
+            "attribute": "Loss"
+          },
+          {
+            "type": "Node",
+            "name": "spill1",
+            "attribute": "Inflow"
+          }
+        ]
+      }
+    ],
+    "outputs": [
+      {
+        "name": "node-outputs",
+        "type": "CSV",
+        "format": "long",
+        "filename": "loss_link2.csv",
+        "metric_set": [
+          "nodes"
+        ],
+        "decimal_places": 1
+      }
+    ]
+  }
+}
diff --git a/pywr-schema/src/test_models/wtw2-expected.csv b/pywr-schema/src/test_models/wtw2-expected.csv
@@ -0,0 +1,13 @@
+time_start,time_end,scenario_index,metric_set,name,attribute,value
+2015-01-01T00:00:00,2015-01-02T00:00:00,0,nodes,wtw1,Inflow,10.0
+2015-01-01T00:00:00,2015-01-02T00:00:00,0,nodes,wtw1,Outflow,10.0
+2015-01-01T00:00:00,2015-01-02T00:00:00,0,nodes,wtw1,Loss,0.0
+2015-01-01T00:00:00,2015-01-02T00:00:00,0,nodes,spill1,Inflow,10.0
+2015-01-02T00:00:00,2015-01-03T00:00:00,0,nodes,wtw1,Inflow,10.0
+2015-01-02T00:00:00,2015-01-03T00:00:00,0,nodes,wtw1,Outflow,10.0
+2015-01-02T00:00:00,2015-01-03T00:00:00,0,nodes,wtw1,Loss,0.0
+2015-01-02T00:00:00,2015-01-03T00:00:00,0,nodes,spill1,Inflow,10.0
+2015-01-03T00:00:00,2015-01-04T00:00:00,0,nodes,wtw1,Inflow,10.0
+2015-01-03T00:00:00,2015-01-04T00:00:00,0,nodes,wtw1,Outflow,10.0
+2015-01-03T00:00:00,2015-01-04T00:00:00,0,nodes,wtw1,Loss,0.0
+2015-01-03T00:00:00,2015-01-04T00:00:00,0,nodes,spill1,Inflow,10.0