Appeal for volunteers and IISfinder documentation fixes

LICENSE

@@ -1,21 +1,10 @@
 MIT License
 
-Copyright (c) 2023 Zuse Institute Berlin (ZIB)
+Copyright (c) 2025 Zuse Institute Berlin (ZIB)
 
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
+Permission is hereby granted, free of charge, to any person  btaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -119,3 +119,23 @@ Please cite [this paper](https://opus4.kobv.de/opus4-zib/frontdoor/index/index/d
 }
 ```
 as well as the corresponding [SCIP Optimization Suite report](https://scip.zib.de/index.php#cite) when you use this tool for a publication or other scientific work.
+
+Seeking Maintainers
+----------------------------------
+
+PySCIPOpt is sustained by volunteer effort, and as the project grows we are inviting more contributors and maintainers to join the team.
+
+What needs to be done
+----------------------
+These are the core responsibilities:
+
+* Community support: Going over the open issues regularly. Occasionally visiting Stack Overflow and OR.SE, as users also ask questions there.
+* PR review: Reviewing user pull requests, making sure that the CHANGELOG is updated, and all added methods are tested.
+* API coverage: keep expanding PySCIPOpt's coverage of SCIP's C API.
+* Documentation: help keep the documentation up to date, and add new tutorials/examples.
+* Releases: there should be a PySCIPOpt release with every SCIP release, at a minimum.
+
+Even if you are not interested in becoming a maintainer, but would like to help out occasionally, that would be very welcome as well!
+
+Send us an email over at **[email protected]** if you're ready to take on the challenge :)
+

docs/tutorials/iis.rst

@@ -33,21 +33,18 @@ Let us create a simple infeasible model and then generate an IIS for it.
 
 .. code-block:: python
 
-    from pyscipopt import Model
+x1 = model.addVar("x1", vtype="B")
+x2 = model.addVar("x2", vtype="B")
+x3 = model.addVar("x3", vtype="B")
 
-    m = Model()
-    x1 = m.addVar("x1", vtype="B")
-    x2 = m.addVar("x2", vtype="B")
-    x3 = m.addVar("x3", vtype="B")
+# These four constraints cannot be satisfied simultaneously
+model.addCons(x1 + x2 == 1, name="c1")
+model.addCons(x2 + x3 == 1, name="c2")
+model.addCons(x1 + x3 == 1, name="c3")
+model.addCons(x1 + x2 + x3 <= 0, name="c4")
 
-    # These four constraints cannot be satisfied simultaneously
-    m.addCons(x1 + x2 == 1, name="c1")
-    m.addCons(x2 + x3 == 1, name="c2")
-    m.addCons(x1 + x3 == 1, name="c3")
-    m.addCons(x1 + x2 + x3 <= 0, name="c4")
-
-  model.optimize()
-  iis = model.generateIIS()
+model.optimize()
+iis = model.generateIIS()
 
 When you run this code, SCIP will output a log showing the progress of finding the IIS:
 
@@ -82,14 +79,14 @@ When you run this code, SCIP will output a log showing the progress of finding t
     Num. Vars. in IIS     : 3
     Num. Bounds in IIS    : 6
 
+After SCIP finds that the model is infeasible, see that SCIP's IIS finders alternate between including constraints to make the problem feasible, and removing constraints to make the problem as small as possible.
+You see in the final statistics that the IIS is indeed irreducible, with 3 variables and 2 constraints.
+
 .. note:: 
    While an already optimized infeasible model is not required to use the IIS functionality, it is
    encouraged to call this functionality only after ``model.optimize()``. Otherwise, SCIP will naturally optimize
    the base problem first to ensure that it is actually infeasible.
 
-    After SCIP finds that the model is infeasible, see that SCIP's IIS finders alternate between including constraints to make the problem feasible, and removing constraints to make the problem as small as possible.
-    You see in the final statistics that the IIS is indeed irreducible, with 3 variables and 2 constraints.
-
 The IIS Object
 ==============
 
@@ -98,7 +95,7 @@ The ``IIS`` object returned by ``generateIIS()`` can be queried to access the fo
 - **time**: The CPU time spent finding the IIS
 - **irreducible**: Boolean indicating if the IIS is irreducible
 - **nodes**: Number of nodes explored during IIS generation
-- **model**: A ``Model`` object containing the subscip with the IIS constraints
+- **subscip**: A ``Model`` object containing the subscip with the IIS constraints
 
 You can interact with the subscip to examine which constraints and variables are part of the IIS:
 
@@ -125,47 +122,31 @@ for identifying infeasible subsystems.
 Basic Structure
 ---------------
 
-To create a custom IIS finder, inherit from the ``IISfinder`` class and implement the ``iisfinderexec`` method:
+To create a custom IIS finder, inherit from the ``IISfinder`` class and implement the ``iisfinderexec`` method.
+This IISfinder just directly removes two constraints in the example above to yield an IIS: 
 
 .. code-block:: python
 
-    from pyscipopt import Model, IISfinder, SCIP_RESULT
+    from pyscipopt import IISfinder, SCIP_RESULT
 
     class SimpleIISFinder(IISfinder):
         """
-        A simple IIS finder that removes constraints one by one
-        until the problem becomes feasible.
+        Minimal working example: keep a known infeasible subset (by name)
+        and mark it as the IIS.
         """
 
         def iisfinderexec(self):
             subscip = self.iis.getSubscip()
-            constraints = subscip.getConss()
-
-            # Start with all constraints
-            active_constraints = set(constraints)
-
-            for cons in constraints:
-                # Temporarily remove the constraint
-                active_constraints.discard(cons)
-
-                # Check if remaining constraints are still infeasible
-                # (This would require setting up a sub-problem with only active_constraints)
-                # For simplicity, we use the full solve approach here
-
-                subscip.freeTransform()
-                subscip.delCons(cons)
-                subscip.optimize()
-
-                if subscip.getStatus() == SCIP_STATUS.INFEASIBLE:
-                    # Still infeasible without this constraint
-                    # Keep it removed
-                    pass
-                else:
-                    # Feasible without it, so constraint is needed in IIS
-                    active_constraints.add(cons)
-                    # In practice, you'd recreate the subscip with all active constraints
-
-            iis.markIrreducible()
+
+            # keep only constraints {c2, c4} and delete others
+            keep = {"c2", "c4"}
+            for cons in list(subscip.getConss()):
+                if cons.name not in keep:
+                    subscip.delCons(cons)
+
+            # Tell SCIP that our sub-SCIP represents an (irreducible) IIS
+            self.iis.setSubscipInfeasible(True)
+            self.iis.setSubscipIrreducible(True)
             return {"result": SCIP_RESULT.SUCCESS}
 
 Including Your Custom IIS Finder
@@ -186,6 +167,7 @@ To use your custom IIS finder, include it in the model before calling ``generate
   model.addCons(x1 + x2 == 1, name="c1")
   model.addCons(x2 + x3 == 1, name="c2")
   model.addCons(x1 + x3 == 1, name="c3")
+  model.addCons(x1 + x2 + x3 <= 0, name="c4")
 
   # Create and include the custom IIS finder
   simple_iis = SimpleIISFinder()

pyproject.toml

@@ -11,7 +11,7 @@ authors = [
 dependencies = ['numpy >=1.16.0']
 requires-python = ">=3.8"
 readme = "README.md"
-license = {text = "MIT"}
+license = {text = "MIT License"}
 classifiers = [
     "Development Status :: 4 - Beta",
     "Intended Audience :: Education",