Merge pull request #103 from arcondello/PresolveImpl-refactor-part2

Refactor presolve methods

Author: arcondello

.circleci/config.yml

@@ -333,24 +333,24 @@ workflows:
           matrix:
             parameters:
               # test the lowest and highest of each minor for the dependencies
-              dimod-version: [==0.12.5, ~=0.12.0]
+              dimod-version: [==0.12.6, ~=0.12.0]
               numpy-version: [==1.20.0, ~=1.23.0]
               python-version: *python-versions
             exclude:
               - numpy-version: ==1.20.0  # NumPy 1.20 does not support 3.10
-                dimod-version: ==0.12.5
+                dimod-version: ==0.12.6
                 python-version: 3.10.0
               - numpy-version: ==1.20.0  # NumPy 1.20 does not support 3.10
                 dimod-version: ~=0.12.0
                 python-version: 3.10.0
               - numpy-version: ==1.20.0  # NumPy 1.20 does not support 3.11
-                dimod-version: ==0.12.5
+                dimod-version: ==0.12.6
                 python-version: 3.11.0
               - numpy-version: ==1.20.0  # NumPy 1.20 does not support 3.11
                 dimod-version: ~=0.12.0
                 python-version: 3.11.0
               - numpy-version: ~=1.23.0  # NumPy 1.23 does not support 3.7
-                dimod-version: ==0.12.5
+                dimod-version: ==0.12.6
                 python-version: 3.7.9
               - numpy-version: ~=1.23.0  # NumPy 1.23 does not support 3.7
                 dimod-version: ~=0.12.0

dwave/preprocessing/include/dwave/flags.hpp

@@ -27,7 +27,17 @@ enum Feasibility {
 enum TechniqueFlags : std::uint64_t {
     None = 0,
 
-    // todo: individual technique flags
+    /// Remove redundant constraints.
+    /// See Achterberg et al., section 3.1.
+    RemoveRedundantConstraints = 1 << 0,
+
+    /// Remove small biases from the objective and constraints.
+    /// See Achterberg et al., section 3.1.
+    RemoveSmallBiases = 1 << 1,
+
+    /// Use constraints to tighten the bounds on variables.
+    /// See Achterberg et al., section 3.2.
+    DomainPropagation = 1 << 2,
 
     All = 0xffffffffffffffffu,
 

dwave/preprocessing/include/dwave/presolve.hpp

@@ -52,6 +52,8 @@ class Presolver {
     /// This clears the model from the presolver.
     model_type detach_model();
 
+    const Feasibility& feasibility() const;
+
     /// Load the default presolve techniques.
     void load_default_presolvers();
 

dwave/preprocessing/libcpp.pxd

@@ -22,7 +22,10 @@ cdef extern from "dwave/exceptions.hpp" namespace "dwave::presolve" nogil:
     pass
 
 cdef extern from "dwave/flags.hpp" namespace "dwave::presolve" nogil:
-    pass
+    enum Feasibility:
+        Unknown,
+        Infeasible,
+        Feasible
 
 cdef extern from "dwave/presolve.hpp" namespace "dwave::presolve" nogil:
     cdef cppclass Presolver[bias_type, index_type, assignment_type]:
@@ -32,6 +35,7 @@ cdef extern from "dwave/presolve.hpp" namespace "dwave::presolve" nogil:
         Presolver(model_type)
         void apply() except+
         model_type detach_model()
+        const Feasibility& feasibility() const
         void load_default_presolvers()
         model_type& model()
         vector[assignment_type] restore(vector[assignment_type])

dwave/preprocessing/presolve/cypresolve.pyx

@@ -27,6 +27,8 @@ from dimod.libcpp cimport ConstrainedQuadraticModel as cppConstrainedQuadraticMo
 from dimod.constrained.cyconstrained cimport cyConstrainedQuadraticModel, make_cqm
 from dimod.cyutilities cimport ConstNumeric
 
+from dwave.preprocessing.libcpp cimport Feasibility as cppFeasibility
+
 # We want to establish a relationship between presolveimpl.hpp and this file, so that
 # changes to presolveimpl.hpp will trigger a rebuild.
 cdef extern from "../src/presolveimpl.hpp" namespace "dwave::presolve" nogil:
@@ -61,6 +63,9 @@ cdef class cyPresolver:
         self.cpppresolver.apply()
         self._model_num_variables = self.cpppresolver.model().num_variables()
 
+        if self.cpppresolver.feasibility() == cppFeasibility.Infeasible:
+            raise RuntimeError("infeasible")
+
     def clear_model(self):
         """Clear the held constrained quadratic model. This is useful to save memory."""
         self.cpppresolver.detach_model()

dwave/preprocessing/src/presolve.cpp

@@ -45,6 +45,11 @@ dimod::ConstrainedQuadraticModel<Bias, Index> Presolver<Bias, Index, Assignment>
     return impl_->detach_model();
 }
 
+template <class Bias, class Index, class Assignment>
+const Feasibility& Presolver<Bias, Index, Assignment>::feasibility() const {
+    return impl_->feasibility();
+}
+
 template <class Bias, class Index, class Assignment>
 void Presolver<Bias, Index, Assignment>::load_default_presolvers() {
     impl_->techniques = TechniqueFlags::Default;