Migrate from cbcbox to mipster for the bundled CBC library

.github/workflows/github-ci.yml

@@ -2,6 +2,10 @@ name: CI
 
 on: [push, pull_request]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
 
   pre-commit:

mip/cbc.py

@@ -70,36 +70,20 @@
         cbclib = ffi.dlopen(libfile)
         os.chdir(old_dir)
     else:
-        import cbcbox as _cbcbox
-
-        _lib_dir = _cbcbox.cbc_lib_dir()
-        if "linux" in platform.lower():
-            if not os_is_64_bit:
-                raise NotImplementedError("Linux 32 bits platform not supported.")
-            libfile = os.path.join(_lib_dir, "libCbc.so")
-        elif platform.lower().startswith("win"):
-            if not os_is_64_bit:
-                raise NotImplementedError("Win32 platform not supported.")
-            # autotools/MinGW places DLLs under bin/, not lib/
-            _bin_dir = os.path.join(_cbcbox.cbc_dist_dir(), "bin")
-            libfile = os.path.join(_bin_dir, "libCbc-0.dll")
-            if not os.path.exists(libfile):
-                raise FileNotFoundError(
-                    "libCbc-0.dll not found in cbcbox Windows distribution at"
-                    " {}. The cbcbox Windows wheel may only contain a static"
-                    " libCbc.a. A shared libCbc-0.dll is required.".format(_bin_dir)
-                )
-            # Python 3.8+ ignores PATH for DLL resolution; use add_dll_directory
+        import mipster as _mipster
+
+        if not os_is_64_bit:
+            raise NotImplementedError("32-bit platforms are not supported.")
+        libfile = _mipster.lib_path()
+        if platform.lower().startswith("win"):
+            # Python 3.8+ ignores PATH for DLL resolution; let Windows find
+            # any sibling DLLs (libgcc, libstdc++, libwinpthread) via
+            # add_dll_directory on the directory holding libmipster-N.dll.
+            _bin_dir = os.path.dirname(libfile)
             if hasattr(os, "add_dll_directory"):
                 os.add_dll_directory(_bin_dir)
             elif _bin_dir not in os.environ.get("PATH", ""):
                 os.environ["PATH"] = _bin_dir + ";" + os.environ["PATH"]
-        elif platform.lower().startswith("darwin") or platform.lower().startswith(
-            "macos"
-        ):
-            libfile = os.path.join(_lib_dir, "libCbc.dylib")
-        else:
-            raise NotImplementedError("Your operating system/platform is not supported")
         cbclib = ffi.dlopen(libfile)
     has_cbc = True
 except Exception as e:
@@ -317,11 +301,6 @@
     void Cbc_setAllowableFractionGap(Cbc_Model *model,
         double allowedFracionGap);
 
-    double Cbc_getAllowablePercentageGap(Cbc_Model *model);
-
-    void Cbc_setAllowablePercentageGap(Cbc_Model *model,
-        double allowedPercentageGap);
-
     double Cbc_getMaximumSeconds(Cbc_Model *model);
 
     void Cbc_setMaximumSeconds(Cbc_Model *model, double maxSeconds);
@@ -1022,7 +1001,9 @@ def clique_merge(self, constrs: Optional[List["mip.Constr"]] = None):
             strengthenPacking = cbclib.Cbc_strengthenPackingRows
             strengthenPacking(self._model, nr, idxr)
 
-    def optimize(self, relax: bool = False, lp_preprocess: bool = False) -> OptimizationStatus:
+    def optimize(
+        self, relax: bool = False, lp_preprocess: bool = False
+    ) -> OptimizationStatus:
         # get name indexes from an osi problem
         def cbc_get_osi_name_indexes(osi_solver) -> Dict[str, int]:
             nameIdx = {}
@@ -1203,7 +1184,9 @@ def cbc_cut_callback(osi_solver, osi_cuts, app_data, depth, npass):
 
         # user-specified cut passes override the cuts-level default
         if self.model.cut_passes != -1:
-            cbclib.Cbc_setIntParam(self._model, INT_PARAM_CUT_PASS, self.model.cut_passes)
+            cbclib.Cbc_setIntParam(
+                self._model, INT_PARAM_CUT_PASS, self.model.cut_passes
+            )
 
         if self.model.clique == 0:
             cbc_set_parameter(self, "clique", "off")
@@ -1662,7 +1645,8 @@ def remove_vars(self, varsList: List[int]):
         cbclib.Cbc_deleteCols(self._model, len(varsList), idx)
 
     def __del__(self):
-        cbclib.Cbc_deleteModel(self._model)
+        if getattr(self, "_model", None) is not None:
+            cbclib.Cbc_deleteModel(self._model)
 
     def get_problem_name(self) -> str:
         namep = self.__name_space
@@ -1793,7 +1777,7 @@ def __clear_sol(self: "SolverOsi"):
         self.__obj_val = None
 
     def __del__(self):
-        if self.owns_solver:
+        if getattr(self, "owns_solver", False):
             cbclib.Osi_deleteSolver(self.osi)
 
     def add_var(

mip/gurobi.py

@@ -428,11 +428,12 @@ def __clear_sol(self):
         self.__obj_val = None
 
     def __del__(self):
-        # freeing Gurobi model and environment
-        if self._ownsModel:
+        # Guard against partially-constructed objects (e.g. PyPy GC may call
+        # __del__ even if __init__ raised before setting these attributes).
+        if getattr(self, "_ownsModel", False):
             if self._model:
                 GRBfreemodel(self._model)
-            if self._env and self._venv_loaded:
+            if self._env and getattr(self, "_venv_loaded", False):
                 GRBfreeenv(self._env)
 
     def add_var(
@@ -589,7 +590,9 @@ def set_max_iter(self, max_iter: int):
     def set_num_threads(self, threads: int):
         self.__threads = threads
 
-    def optimize(self, relax: bool = False, lp_preprocess: bool = False) -> OptimizationStatus:
+    def optimize(
+        self, relax: bool = False, lp_preprocess: bool = False
+    ) -> OptimizationStatus:
 
         # todo add branch_selector and incumbent_updater callbacks
         @ffi.callback(
@@ -802,9 +805,7 @@ def callback(
                 self.__obj_val = self.get_dbl_attr("ObjVal")
                 self.__x = ffi.new("double[{}]".format(self.num_cols()))
                 attr = "X".encode("utf-8")
-                st = GRBgetdblattrarray(
-                    self._model, attr, 0, self.num_cols(), self.__x
-                )
+                st = GRBgetdblattrarray(self._model, attr, 0, self.num_cols(), self.__x)
                 if st:
                     raise ParameterNotAvailable("Error querying Gurobi solution")
                 # duals are only valid at optimality for Gurobi, skip Pi/RC