add specification errors and raise when infeasible capacitated p_medi…

…an is requested
ljwolf · Mar 1, 2023 · d99315f · d99315f
1 parent 47abb42
commit d99315f
Show file tree

Hide file tree

Showing 3 changed files with 16 additions and 3 deletions.
diff --git a/spopt/locate/base.py b/spopt/locate/base.py
@@ -16,6 +16,8 @@
     -3: "Undefined",
 }
 
+class SpecificationError(pulp.PulpError):
+    pass
 
 class LocateSolver(BaseSpOptExactSolver):
     """Base class for the ``locate`` package."""

diff --git a/spopt/locate/coverage.py b/spopt/locate/coverage.py
@@ -9,6 +9,7 @@
     BackupPercentageMixinMixin,
     LocateSolver,
     FacilityModelBuilder,
+    SpecificationError
 )
 from scipy.spatial.distance import cdist
 
@@ -227,7 +228,7 @@ def from_cost_matrix(
         lscp = LSCP(name, model)
 
         if demand_quantity_arr is not None and facility_capacity_arr is None:
-            raise ValueError(
+            raise SpecificationError(
                 "Demand quantities supplied with no facility capacities. "
                 "Model cannot satisfy clients with different "
                 "demands without facility capacities."
@@ -250,7 +251,7 @@ def from_cost_matrix(
             sum_demand = demand_quantity_arr.sum()
             sum_capacity = facility_capacity_arr.sum()
             if sum_demand > sum_capacity:
-                raise ValueError(
+                raise SpecificationError(
                     f"Infeasible model. Demand greater than capacity "
                     f"({sum_demand} > {sum_capacity})."
                 )
@@ -404,7 +405,7 @@ def from_geodataframe(
             facility_capacity_arr = gdf_fac[facility_capacity_col].to_numpy()
 
         if demand_quantity_arr is not None and facility_capacity_arr is None:
-            raise ValueError(
+            raise SpecificationError(
                 "Demand quantities supplied with no facility capacities. "
                 "Model cannot satisfy clients with different "
                 "demands without facility capacities."

diff --git a/spopt/locate/p_median.py b/spopt/locate/p_median.py
@@ -8,6 +8,7 @@
     LocateSolver,
     FacilityModelBuilder,
     MeanDistanceMixin,
+    SpecificationError
 )
 from scipy.spatial.distance import cdist
 
@@ -252,6 +253,15 @@ def from_cost_matrix(
                 p_median, predefined_facilities_arr
             )
         if facility_capacities is not None:
+            sorted_capacities = np.sort(facility_capacities)
+            highest_possible_capacity = sorted_capacities[-p_facilities:].sum() 
+            if highest_possible_capacity < weights.sum(): 
+                raise SpecificationError(f"""
+                    Problem is infeasible. The highest possible capacity 
+                    {highest_possible_capacity}, coming from the {p_facilities}
+                    sites with the highest capacity, is smaller than the total demand {weights.sum()}.
+                    """
+                    )
             FacilityModelBuilder.add_facility_capacity_constraint(
                 p_median,
                 weights,