Use cbcbox for CBC binaries, drop bundled libs

- Replace bundled CBC binaries with cbcbox package dependency
- Simplify cbc.py library loading: cbcbox is primary source,
  PMIP_CBC_LIBRARY env var still supported for custom builds
- Remove os.chdir() workaround (cbcbox uses proper $ORIGIN rpath)
- Remove mip/libraries/ bundled .so/.dylib/.dll files
- Remove [tool.setuptools.package-data] for libraries
- Bump requires-python to >=3.8 (cbcbox minimum)
- Update classifiers: explicit OS/Python version coverage (3.8-3.13,
  Linux x86_64/aarch64, macOS x86_64/arm64, Windows x64)
- CI: update PyPy pypy3.9 -> pypy3.11 (latest stable)
- CI: remove macOS PyPy exclusion (was CBC bug, fixed in cbcbox)
- CI: remove stale Windows/ubuntu-3.9 exclusion for highsbox
- examples/tsp-compact-ulysses22.py: replace max_nodes_same_incumbent
  (unsupported in new CBC) with max_nodes=500

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: h-g-s

.github/workflows/github-ci.yml

@@ -39,14 +39,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "pypy3.9-v7.3.15"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "pypy3.11"]
         os: [macos-14, macos-15, ubuntu-22.04, ubuntu-24.04, windows-2025, windows-2022]
-        exclude:
-          # temporarily exclude pypy3 on mac-os as there failing tests caused by bug on cbc side
-          - os: macos-14
-            python-version: "pypy3.9-v7.3.15"
-          - os: macos-15
-            python-version: "pypy3.9-v7.3.15"
 
     steps:
 
@@ -57,6 +51,7 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
         architecture: x64
+        allow-prereleases: false
 
     - name: Cache pip dependencies
       uses: actions/cache@v4
@@ -77,11 +72,10 @@ jobs:
       run: python -m pip install .[test,numpy]
 
     - name: Install gurobi
-      if: ${{ matrix.python-version != 'pypy3.9-v7.3.15' }}
+      if: ${{ !startsWith(matrix.python-version, 'pypy') }}
       run: python -m pip install .[gurobi]
 
     - name: Install highs
-      if: ${{ !contains(matrix.os, 'windows') && !(contains(matrix.os, 'ubuntu') && matrix.python-version == '3.9') }}
       run: python -m pip install .[highs]
 
     - name: list installed packages

examples/tsp-compact-ulysses22.py

@@ -98,7 +98,7 @@ def dist(p1: Tuple[float, float], p2: Tuple[float, float]) -> float:
         model += y[i] - (n + 1) * x[i][j] >= y[j] - n
 
 # optimizing
-model.optimize(max_nodes_same_incumbent=1000)
+model.optimize(max_nodes=500)
 
 # checking if a solution was found
 if model.num_solutions:

mip/cbc.py

@@ -3,8 +3,7 @@
 import logging
 from typing import Dict, List, Tuple, Optional, Union
 from sys import platform, maxsize
-from os.path import dirname, isfile, exists
-from platform import machine as platform_machine
+from os.path import dirname
 import os
 import multiprocessing as multip
 import numbers
@@ -56,58 +55,43 @@
 DEF_PUMPP = 30
 
 try:
-    pathmip = dirname(mip.__file__)
-    pathlib = os.path.join(pathmip, "libraries")
     libfile = ""
-    # if user wants to force the loading of an specific CBC library
-    # (for debugging purposes, for example)
+    # if user wants to force the loading of a specific CBC library
     if "PMIP_CBC_LIBRARY" in os.environ:
         libfile = os.environ["PMIP_CBC_LIBRARY"]
         pathlib = dirname(libfile)
-
         if platform.lower().startswith("win"):
             if pathlib not in os.environ["PATH"]:
                 os.environ["PATH"] += ";" + pathlib
+        old_dir = os.getcwd()
+        os.chdir(pathlib)
+        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 os_is_64_bit:
-                pathlibe = pathlib
-                libfile = os.path.join(pathlib, "cbc-c-linux-x86-64.so")
-                if not exists(libfile):
-                    pathlibe = pathlib
-                    libfile = os.path.join(pathlib, "cbc-c-linux-x86-64.so")
-                pathlib = pathlibe
-            else:
+            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 os_is_64_bit:
-                pathlibe = os.path.join(pathlib, "win64")
-                libfile = os.path.join(pathlibe, "cbc-c-windows-x86-64.dll")
-                if exists(libfile):
-                    if pathlibe not in os.environ["PATH"]:
-                        os.environ["PATH"] = pathlibe + ";" + os.environ["PATH"]
-                else:
-                    pathlibe = pathlib
-                    libfile = os.path.join(pathlibe, "cbc-c-windows-x86-64.dll")
-                    if pathlibe not in os.environ["PATH"]:
-                        os.environ["PATH"] = pathlibe + ";" + os.environ["PATH"]
-                pathlib = pathlibe
-
-            else:
+            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.dll")
+            if _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"
         ):
-            if platform_machine().lower().startswith("arm64"):
-                libfile = os.path.join(pathlib, "cbc-c-darwin-arm64.dylib")
-            elif os_is_64_bit:
-                libfile = os.path.join(pathlib, "cbc-c-darwin-x86-64.dylib")
-        if not libfile:
-            raise NotImplementedError("You operating system/platform is not supported")
-    old_dir = os.getcwd()
-    os.chdir(pathlib)
-    cbclib = ffi.dlopen(libfile)
-    os.chdir(old_dir)
+            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:
     logger.error("An error occurred while loading the CBC library:\t " "{}\n".format(e))