Make WarmStartComponent use Extractor

miplearn/extractors.py

@@ -25,6 +25,23 @@ class Extractor(ABC):
                 result[category] += [(var, index)]
         return result
     
+    @staticmethod
+    def merge(partial_results, vertical=False):
+        results = {}
+        all_categories = set()
+        for pr in partial_results:
+            all_categories |= pr.keys()
+        for category in all_categories:
+            results[category] = []
+            for pr in partial_results:
+                if category in pr.keys():
+                    results[category] += [pr[category]]
+            if vertical:
+                results[category] = np.vstack(results[category])
+            else:
+                results[category] = np.hstack(results[category])
+        return results
+
 
 class UserFeaturesExtractor(Extractor):
     def extract(self,
@@ -61,10 +78,20 @@ class SolutionExtractor(Extractor):
                 if category not in result.keys():
                     result[category] = []
                 for (var, index) in var_index_pairs:
-                    result[category] += [[
-                        1 - var[index].value,
-                        var[index].value,
-                    ]]
+                    v = var[index].value
+                    if v is None:
+                        result[category] += [[0, 0]]
+                    else:
+                        result[category] += [[1 - v, v]]
         for category in result.keys():
             result[category] = np.vstack(result[category])            
         return result
+    
+    
+class CombinedExtractor(Extractor):
+    def __init__(self, extractors):
+        self.extractors = extractors
+    
+    def extract(self, instances, models):
+        return self.merge([ex.extract(instances, models)
+                           for ex in self.extractors])

miplearn/solvers.py

@@ -2,7 +2,6 @@
 # Copyright (C) 2019-2020 Argonne National Laboratory. All rights reserved.
 # Written by Alinson S. Xavier <axavier@anl.gov>
 
-from .transformers import PerVariableTransformer
 from .warmstart import WarmStartComponent
 from .branching import BranchPriorityComponent
 import pyomo.environ as pe
@@ -66,6 +65,12 @@ class LearningSolver:
     def solve(self, instance, tee=False):
         model = instance.to_model()
         
+        # Solve linear relaxation (TODO: use solver provided by user)
+        lr_solver = pe.SolverFactory("gurobi")
+        lr_solver.options["threads"] = 4
+        lr_solver.options["relax_integrality"] = 1
+        lr_solver.solve(model)
+
         self._create_solver()
         if self.is_persistent:
             self.internal_solver.set_instance(model)

miplearn/tests/test_extractors.py

@@ -3,8 +3,10 @@
 # Written by Alinson S. Xavier <axavier@anl.gov>
 
 from miplearn.problems.knapsack import KnapsackInstance
-from miplearn import (UserFeaturesExtractor,
-                      SolutionExtractor)
+from miplearn.extractors import (UserFeaturesExtractor,
+                                 SolutionExtractor,
+                                 CombinedExtractor,
+                                )
 import numpy as np
 import pyomo.environ as pe
 
@@ -52,3 +54,16 @@ def test_solution_extractor():
         0., 1.,
         1., 0.,
     ]
+
+    
+def test_combined_extractor():
+    instances = _get_instances()
+    models = [instance.to_model() for instance in instances]
+    extractor = CombinedExtractor(extractors=[UserFeaturesExtractor(),
+                                              SolutionExtractor()])
+    features = extractor.extract(instances, models)
+    assert isinstance(features, dict)
+    assert "default" in features.keys()
+    assert isinstance(features["default"], np.ndarray)
+    assert features["default"].shape == (6, 6)
+    

miplearn/tests/test_warmstart.py

@@ -24,7 +24,7 @@ def test_warm_start_save_load():
     solver.parallel_solve(_get_instances(), n_jobs=2)
     solver.fit()
     comp = solver.components["warm-start"]
-    assert comp.x_train["default"].shape == (8, 4)
+    assert comp.x_train["default"].shape == (8, 6)
     assert comp.y_train["default"].shape == (8, 2)
     assert "default" in comp.predictors.keys()
     solver.save_state(state_file.name)
@@ -32,6 +32,6 @@ def test_warm_start_save_load():
     solver = LearningSolver(components={"warm-start": WarmStartComponent()})
     solver.load_state(state_file.name)
     comp = solver.components["warm-start"]
-    assert comp.x_train["default"].shape == (8, 4)
+    assert comp.x_train["default"].shape == (8, 6)
     assert comp.y_train["default"].shape == (8, 2)
     assert "default" in comp.predictors.keys()

miplearn/warmstart.py

@@ -4,6 +4,7 @@
 
 from . import Component
 from .transformers import PerVariableTransformer
+from .extractors import *
 
 from abc import ABC, abstractmethod
 from copy import deepcopy
@@ -131,24 +132,21 @@ class WarmStartComponent(Component):
         self.predictor_prototype = predictor_prototype
     
     def before_solve(self, solver, instance, model):
-        var_split = self.transformer.split_variables(instance, model)
-        x_test = {}
+        # Build x_test
+        x_test = CombinedExtractor([UserFeaturesExtractor(),
+                                    SolutionExtractor(),
+                                   ]).extract([instance], [model])
         
-        # Collect training data (x_train) and build x_test
-        for category in var_split.keys():
-            var_index_pairs = var_split[category]
-            x = self.transformer.transform_instance(instance, var_index_pairs)
-            x_test[category] = x
-            if category not in self.x_train.keys():
-                self.x_train[category] = x
-            else:
-                assert x.shape[1] == self.x_train[category].shape[1]
-                self.x_train[category] = np.vstack([self.x_train[category], x])
+        # Update self.x_train
+        self.x_train = Extractor.merge([self.x_train, x_test],
+                                       vertical=True)
         
         # Predict solutions
+        var_split = Extractor.split_variables(instance, model)
         for category in var_split.keys():
             var_index_pairs = var_split[category]
-            if category in self.predictors.keys():
+            if category not in self.predictors.keys():
+                continue
             ws = self.predictors[category].predict(x_test[category])
             assert ws.shape == (len(var_index_pairs), 2)
             for i in range(len(var_index_pairs)):
@@ -169,14 +167,8 @@ class WarmStartComponent(Component):
                         var[index].value = 1
 
     def after_solve(self, solver, instance, model):
-        var_split = self.transformer.split_variables(instance, model)
-        for category in var_split.keys():
-            var_index_pairs = var_split[category]
-            y = self.transformer.transform_solution(var_index_pairs)
-            if category not in self.y_train.keys():
-                self.y_train[category] = y
-            else:
-                self.y_train[category] = np.vstack([self.y_train[category], y])
+        y_test = SolutionExtractor().extract([instance], [model])
+        self.y_train = Extractor.merge([self.y_train, y_test], vertical=True)        
                 
     def fit(self, solver, n_jobs=1):
         for category in tqdm(self.x_train.keys(), desc="Warm start"):