Add event callback to solver backend to monitor progress (#56)

* feat: add event callback

* lint

* add some data

* simplify code

* working for gurobi

* remove std::visit

* fix windows

* add test and typing

Makefile

@@ -14,3 +14,6 @@ clean:
 	rm -rf build dist
 	rm -rf ilpy/*.cpp
 	rm -rf ilpy/*.so
+
+build:
+	python setup.py build_ext --inplace

ilpy/_functional.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Iterable, Literal, Sequence, Tuple
+from typing import TYPE_CHECKING, Callable, Iterable, Literal, Mapping, Sequence, Tuple
 
 from .expressions import Expression
 from .wrapper import (
@@ -27,6 +27,7 @@ def solve(
     variable_type: VariableTypeType = VariableType.Continuous,
     verbose: bool = False,
     preference: PreferenceType = Preference.Any,
+    on_event: Callable[[Mapping], None] | None = None,
 ) -> list[float]:
     """Solve an objective subject to constraints.
 
@@ -56,6 +57,10 @@ def solve(
     preference : Preference | Literal["any", "cplex", "gurobi", "scip"]
         Backend preference, either an `ilpy.Preference` or a string in
         {"any", "cplex", "gurobi", "scip"}.  By default, `Preference.Any`.
+    on_event : Callable[[Mapping], None], optional
+        A callback function that is called when an event occurs, by default None.
+        The callback function should accept a dict which will contain event
+        metadata.
 
     Returns
     -------
@@ -92,6 +97,7 @@ def solve(
             )
         solver.add_constraint(const)
 
+    solver.set_event_callback(on_event)
     solution = solver.solve()
     return list(solution)  # type: ignore
 

ilpy/decl.pxd

@@ -4,6 +4,7 @@ from libcpp.memory cimport shared_ptr
 from libcpp.map cimport map
 from libcpp.pair cimport pair
 from libcpp.vector cimport vector
+from cpython.object cimport PyObject
 
 cdef extern from "impl/solvers/Relation.h":
     cdef enum Relation:
@@ -99,6 +100,7 @@ cdef extern from "impl/solvers/SolverBackend.h":
         void setNumThreads(unsigned int)
         void setVerbose(bool)
         bool solve(Solution& solution, string& message) except +
+        void setEventCallback(PyObject* callback)
 
 cdef extern from "impl/solvers/ScipBackend.cpp":
     pass