Capture solver output in Python

metab0t · metab0t · commit e089ad4fdad7 · 2025-12-11T17:17:27.000+08:00
diff --git a/include/pyoptinterface/copt_model.hpp b/include/pyoptinterface/copt_model.hpp
@@ -98,7 +98,8 @@ extern "C"
 	B(COPT_GetColUpperIIS);        \
 	B(COPT_GetRowLowerIIS);        \
 	B(COPT_GetRowUpperIIS);        \
-	B(COPT_GetSOSIIS);
+	B(COPT_GetSOSIIS);             \
+	B(COPT_SetLogCallback);
 
 namespace copt
 {
@@ -170,6 +171,13 @@ struct COPTCallbackUserdata
 	bool cb_requires_submit_solution = false;
 };
 
+using COPTLoggingCallback = std::function<void(const char *)>;
+
+struct COPTLoggingCallbackUserdata
+{
+	COPTLoggingCallback callback;
+};
+
 class COPTModel : public OnesideLinearConstraintMixin<COPTModel>,
                   public TwosideLinearConstraintMixin<COPTModel>,
                   public OnesideQuadraticConstraintMixin<COPTModel>,
@@ -304,6 +312,11 @@ class COPTModel : public OnesideLinearConstraintMixin<COPTModel>,
 	int _constraint_index(const ConstraintIndex &constraint);
 	int _checked_constraint_index(const ConstraintIndex &constraint);
 
+	// Control logging
+	void set_logging(const COPTLoggingCallback &callback);
+
+	COPTLoggingCallbackUserdata m_logging_callback_userdata;
+
 	// Callback
 	void set_callback(const COPTCallback &callback, int cbctx);
 
diff --git a/include/pyoptinterface/gurobi_model.hpp b/include/pyoptinterface/gurobi_model.hpp
@@ -73,6 +73,7 @@
 	B(GRBloadenv);            \
 	B(GRBfreeenv);            \
 	B(GRBstartenv);           \
+	B(GRBsetlogcallbackfunc); \
 	B(GRBconverttofixed);     \
 	B(GRBcomputeIIS);
 
@@ -104,10 +105,7 @@ class GurobiEnv
 
 	void check_error(int error);
 
-  private:
 	GRBenv *m_env = nullptr;
-
-	friend class GurobiModel;
 };
 
 struct GRBfreemodelT
@@ -138,6 +136,13 @@ struct GurobiCallbackUserdata
 	bool cb_requires_submit_solution = false;
 };
 
+using GurobiLoggingCallback = std::function<void(const char *)>;
+
+struct GurobiLoggingCallbackUserdata
+{
+	GurobiLoggingCallback callback;
+};
+
 class GurobiModel : public OnesideLinearConstraintMixin<GurobiModel>,
                     public OnesideQuadraticConstraintMixin<GurobiModel>,
                     public TwosideNLConstraintMixin<GurobiModel>,
@@ -293,6 +298,11 @@ class GurobiModel : public OnesideLinearConstraintMixin<GurobiModel>,
 	// Non-exported functions
 	void check_error(int error);
 
+	// Control logging
+	void set_logging(const GurobiLoggingCallback &callback);
+
+	GurobiLoggingCallbackUserdata m_logging_callback_userdata;
+
 	// Callback
 	void set_callback(const GurobiCallback &callback);
 
diff --git a/include/pyoptinterface/mosek_model.hpp b/include/pyoptinterface/mosek_model.hpp
@@ -121,6 +121,13 @@ struct MOSEKfreemodelT
 	};
 };
 
+using MOSEKLoggingCallback = std::function<void(const char *)>;
+
+struct MOSEKLoggingCallbackUserdata
+{
+	MOSEKLoggingCallback callback;
+};
+
 class MOSEKModel : public OnesideLinearConstraintMixin<MOSEKModel>,
                    public TwosideLinearConstraintMixin<MOSEKModel>,
                    public OnesideQuadraticConstraintMixin<MOSEKModel>,
@@ -206,7 +213,6 @@ class MOSEKModel : public OnesideLinearConstraintMixin<MOSEKModel>,
 	double getprimalobj();
 	double getdualobj();
 
-	void enable_log();
 	void disable_log();
 
 	// Accessing information of problem
@@ -246,6 +252,11 @@ class MOSEKModel : public OnesideLinearConstraintMixin<MOSEKModel>,
 	MSKint32t _constraint_index(const ConstraintIndex &constraint);
 	MSKint32t _checked_constraint_index(const ConstraintIndex &constraint);
 
+	// Control logging
+	void set_logging(const MOSEKLoggingCallback &callback);
+
+	MOSEKLoggingCallbackUserdata m_logging_callback_userdata;
+
   private:
 	MonotoneIndexer<MSKint32t> m_variable_index;
 
diff --git a/lib/copt_model.cpp b/lib/copt_model.cpp
@@ -1390,8 +1390,24 @@ void COPTEnvConfig::set(const char *param_name, const char *value)
 	check_error(error);
 }
 
+// Logging callback
+static void RealLoggingCallbackFunction(char *msg, void *logdata)
+{
+	auto real_logdata = static_cast<COPTLoggingCallbackUserdata *>(logdata);
+	auto &callback = real_logdata->callback;
+	callback(msg);
+}
+
+void COPTModel::set_logging(const COPTLoggingCallback &callback)
+{
+	m_logging_callback_userdata.callback = callback;
+	int error = copt::COPT_SetLogCallback(m_model.get(), &RealLoggingCallbackFunction,
+	                                      &m_logging_callback_userdata);
+	check_error(error);
+}
+
 // Callback
-int RealCOPTCallbackFunction(copt_prob *prob, void *cbdata, int cbctx, void *userdata)
+static int RealCOPTCallbackFunction(copt_prob *prob, void *cbdata, int cbctx, void *userdata)
 {
 	auto real_userdata = static_cast<COPTCallbackUserdata *>(userdata);
 	auto model = static_cast<COPTModel *>(real_userdata->model);
diff --git a/lib/copt_model_ext.cpp b/lib/copt_model_ext.cpp
@@ -149,6 +149,8 @@ NB_MODULE(copt_model_ext, m)
 	    BIND_F(version_string)
 	    BIND_F(get_raw_model)
 
+		BIND_F(set_logging)
+
 		BIND_F(set_callback)
 		BIND_F(cb_get_info_int)
 		BIND_F(cb_get_info_double)
diff --git a/lib/gurobi_model.cpp b/lib/gurobi_model.cpp
@@ -1404,8 +1404,25 @@ void GurobiEnv::check_error(int error)
 	}
 }
 
+// Logging callback
+static int RealLoggingCallbackFunction(char *msg, void *logdata)
+{
+	auto real_logdata = static_cast<GurobiLoggingCallbackUserdata *>(logdata);
+	auto &callback = real_logdata->callback;
+	callback(msg);
+	return 0;
+}
+
+void GurobiModel::set_logging(const GurobiLoggingCallback &callback)
+{
+	m_logging_callback_userdata.callback = callback;
+	int error = gurobi::GRBsetlogcallbackfunc(m_model.get(), &RealLoggingCallbackFunction,
+	                                          &m_logging_callback_userdata);
+	check_error(error);
+}
+
 // Callback
-int RealGurobiCallbackFunction(GRBmodel *, void *cbdata, int where, void *usrdata)
+static int RealGurobiCallbackFunction(GRBmodel *, void *cbdata, int where, void *usrdata)
 {
 	auto real_userdata = static_cast<GurobiCallbackUserdata *>(usrdata);
 	auto model = static_cast<GurobiModel *>(real_userdata->model);
diff --git a/lib/gurobi_model_ext.cpp b/lib/gurobi_model_ext.cpp
@@ -153,6 +153,8 @@ NB_MODULE(gurobi_model_ext, m)
 		BIND_F(version_string)
 		BIND_F(get_raw_model)
 
+		BIND_F(set_logging)
+
 		BIND_F(set_callback)
 		BIND_F(cb_get_info_int)
 		BIND_F(cb_get_info_double)
diff --git a/lib/mosek_model.cpp b/lib/mosek_model.cpp
@@ -940,17 +940,6 @@ double MOSEKModel::getdualobj()
 	return retval;
 }
 
-static void printstr(void *handle, const char *str)
-{
-	printf("%s", str);
-	fflush(stdout);
-}
-void MOSEKModel::enable_log()
-{
-	auto error = mosek::MSK_linkfunctotaskstream(m_model.get(), MSK_STREAM_LOG, NULL, printstr);
-	check_error(error);
-}
-
 void MOSEKModel::disable_log()
 {
 	auto error = mosek::MSK_linkfunctotaskstream(m_model.get(), MSK_STREAM_LOG, NULL, NULL);
@@ -1402,6 +1391,22 @@ MSKint32t MOSEKModel::_checked_constraint_index(const ConstraintIndex &constrain
 	return row;
 }
 
+// Logging callback
+static void RealLoggingCallbackFunction(void *handle, const char *msg)
+{
+	auto real_logdata = static_cast<MOSEKLoggingCallbackUserdata *>(handle);
+	auto &callback = real_logdata->callback;
+	callback(msg);
+}
+
+void MOSEKModel::set_logging(const MOSEKLoggingCallback &callback)
+{
+	m_logging_callback_userdata.callback = callback;
+	auto error = mosek::MSK_linkfunctotaskstream(
+	    m_model.get(), MSK_STREAM_LOG, &m_logging_callback_userdata, &RealLoggingCallbackFunction);
+	check_error(error);
+}
+
 void *MOSEKModel::get_raw_model()
 {
 	return m_model.get();
diff --git a/lib/mosek_model_ext.cpp b/lib/mosek_model_ext.cpp
@@ -2,6 +2,7 @@
 #include <nanobind/stl/tuple.h>
 #include <nanobind/stl/string.h>
 #include <nanobind/stl/vector.h>
+#include <nanobind/stl/function.h>
 
 #include "pyoptinterface/mosek_model.hpp"
 
@@ -135,7 +136,7 @@ NB_MODULE(mosek_model_ext, m)
 		BIND_F(getprimalobj)
 		BIND_F(getdualobj)
 
-	    BIND_F(enable_log)
+		BIND_F(set_logging)
 	    BIND_F(disable_log)
 
 	    BIND_F(set_variable_name)
diff --git a/src/pyoptinterface/_src/copt.py b/src/pyoptinterface/_src/copt.py
@@ -384,6 +384,10 @@ def __init__(self, env=None):
         self.variable_start_values: Dict[VariableIndex, float] = dict()
         self.nl_start_values: Dict[VariableIndex, float] = dict()
 
+        # override logging
+        self.set_raw_parameter("LogToConsole", 0)
+        self.set_logging(print)
+
     def add_variables(self, *args, **kwargs):
         return make_variable_tupledict(self, *args, **kwargs)
 
diff --git a/src/pyoptinterface/_src/gurobi.py b/src/pyoptinterface/_src/gurobi.py
@@ -1,5 +1,3 @@
-# try to load DLL of gurobi in${GUROBI_HOME}/bin
-# only on windows
 import os
 import platform
 from pathlib import Path
@@ -550,6 +548,11 @@ def __init__(self, env=None):
         # We must keep a reference to the environment to prevent it from being garbage collected
         self._env = env
 
+        # Replace default logging behavior to use Python print
+        # otherwise it prints directly to stdout/stderr bypassing Python and causing issues in Jupyter notebooks
+        self.set_raw_parameter("LogToConsole", 0)
+        self.set_logging(lambda msg: print(msg, end=""))
+
     @staticmethod
     def supports_variable_attribute(attribute: VariableAttribute, settable=False):
         if settable:
diff --git a/src/pyoptinterface/_src/mosek.py b/src/pyoptinterface/_src/mosek.py
@@ -308,7 +308,7 @@ def set_silent(model, value: bool):
     if value:
         model.disable_log()
     else:
-        model.enable_log()
+        model.set_logging(lambda msg: print(msg, end=""))
 
 
 model_attribute_set_func_map = {
@@ -364,7 +364,8 @@ def __init__(self, env=None):
         # We must keep a reference to the environment to prevent it from being garbage collected
         self._env = env
         self.last_solve_return_code: Optional[int] = None
-        self.silent = True
+        self.silent = False
+        self.set_logging(lambda msg: print(msg, end=""))
 
     @staticmethod
     def supports_variable_attribute(attribute: VariableAttribute, settable=False):
