Merge branch 'highs' derived from PR #332

.github/workflows/github-ci.yml

@@ -10,10 +10,10 @@ jobs:
 
     steps:
 
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v3
 
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v4
         with:
           python-version: 3.11
 
@@ -50,10 +50,10 @@ jobs:
 
     steps:
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v3
 
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v5
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
         architecture: x64
@@ -65,23 +65,19 @@ jobs:
     - name: Upgrade pip
       run: python -m pip install --upgrade pip
 
-    - name: Install mip for testing (PyPy)
-      if: ${{ matrix.python-version == 'pypy3.9-v7.3.15' }}
+    - name: Install test and numpy
       run: python -m pip install .[test,numpy]
 
-    - name: Install mip for testing (CPython)
+    - name: Install gurobi
       if: ${{ matrix.python-version != 'pypy3.9-v7.3.15' }}
-      run: python -m pip install .[test,numpy,gurobi]
+      run: python -m pip install .[gurobi]
+
+    - name: Install highs
+      if: ${{ !contains(matrix.os, 'windows') && !(matrix.os == 'ubuntu-22.04' && matrix.python-version == '3.9') }}
+      run: python -m pip install .[highs]
 
     - name: list installed packages
       run: python -m pip list
 
-    - name: Run tests PyPy
-      if: ${{ matrix.python-version == 'pypy3.9-v7.3.15'}}
-      run: |
-        python -m pytest test --verbose --color=yes --doctest-modules --ignore="test/test_gurobi.py"
-
     - name: Run tests
-      if: ${{ matrix.python-version != 'pypy3.9-v7.3.15'}}
-      run: |
-        python -m pytest test --verbose --color=yes --doctest-modules -Werror
+      run: python -m pytest test --verbose --color=yes --doctest-modules -Werror

examples/gen_cuts_mip.py

@@ -1,23 +1,21 @@
 """This example reads a MIP (in .lp or .mps), solves its linear programming
 relaxation and then tests the impact of adding different types of cutting
-planes. In the end, the it informs which cut generator produced the best bound
-improvement."""
+planes. In the end, it informs which cut generator produced the best bound
+improvement.
+"""
 
 from textwrap import shorten
-import sys
 from mip import Model, CutType, OptimizationStatus
 import mip
 
-lp_path = ""
-
 #  using test data
 lp_path = mip.__file__.replace("mip/__init__.py", "test/data/1443_0-9.lp").replace(
     "mip\\__init__.py", "test\\data\\1443_0-9.lp"
 )
 
 m = Model()
-if m.solver_name.upper() in ["GRB", "GUROBI"]:
-    print("This feature is currently not supported in Gurobi.")
+if m.solver_name.upper() != mip.CBC:
+    print("This feature is currently supported only in CBC.")
 else:
     m.read(lp_path)
 
@@ -55,8 +53,8 @@
                 best_cut = ct
 
             print(
-                "Linear programming relaxation bound now: %g, improvement of %.2f"
-                % (m2.objective_value, perc_impr)
+                f"Linear programming relaxation bound now: "
+                f"{m2.objective_value:.2f}, improvement of {perc_impr:.2f}"
             )
         else:
             continue

mip/__init__.py

@@ -7,6 +7,10 @@
 from mip.ndarray import LinExprTensor
 from mip.entities import Column, Constr, LinExpr, Var, ConflictGraph
 from mip.model import *
-from mip._version import __version__
+
+try:
+    from ._version import __version__
+except ImportError:
+    __version__ = "unknown"
 
 name = "mip"

mip/constants.py

@@ -29,6 +29,7 @@
 CPLEX = "CPX"  # we plan to support CPLEX in the future
 GRB = "GRB"
 GUROBI = "GRB"
+HIGHS = "HiGHS"
 SCIP = "SCIP"  # we plan to support SCIP in the future
 
 # variable types

mip/gurobi.py

@@ -51,6 +51,7 @@
 MAX_NAME_SIZE = 512  # for variables and constraints
 
 lib_path = None
+has_gurobi = False
 
 if "GUROBI_HOME" in environ:
     if platform.lower().startswith("win"):
@@ -93,9 +94,9 @@
 
 
 if lib_path is None:
-    found = False
+    has_gurobi = False
 else:
-    found = True
+    has_gurobi = True
     grblib = ffi.dlopen(lib_path)
 
     ffi.cdef(
@@ -339,7 +340,7 @@ class SolverGurobi(Solver):
     def __init__(self, model: Model, name: str, sense: str, modelp: CData = ffi.NULL):
         """modelp should be informed if a model should not be created,
         but only allow access to an existing one"""
-        if not found:
+        if not has_gurobi:
             raise FileNotFoundError(
                 """Gurobi not found. Plase check if the
             Gurobi dynamic loadable library is reachable or define