refactor(logger): give each component library its own logger

cpp/CMakeLists.txt

@@ -569,6 +569,12 @@ target_compile_definitions(cuopt_objs
   PUBLIC CUSPARSE_ENABLE_EXPERIMENTAL_API
 )
 
+# Lets callers reach routing's logger through init_component_logger_t. Routing is optional,
+# so the entry point it declares is only linkable when routing was actually built.
+if(NOT SKIP_ROUTING_BUILD)
+  target_compile_definitions(cuopt_objs PUBLIC CUOPT_HAS_ROUTING)
+endif()
+
 target_compile_options(cuopt_objs
         PRIVATE "$<$<COMPILE_LANGUAGE:CXX>:${CUOPT_CXX_FLAGS}>"
         "$<$<COMPILE_LANGUAGE:CUDA>:${CUOPT_CUDA_FLAGS}>"

cpp/cuopt_cli.cpp

@@ -100,8 +100,15 @@ int run_single_file(const std::string& file_path,
                     cuopt::mathematical_optimization::io::mps_reader_type_t mps_reader,
                     cuopt::mathematical_optimization::solver_settings_t<int, double>& settings)
 {
-  cuopt::init_logger_t log(settings.get_parameter<std::string>(CUOPT_LOG_FILE),
-                           settings.get_parameter<bool>(CUOPT_LOG_TO_CONSOLE));
+  // The solver's logger lives in the solver library and is not reachable from here, so
+  // configure it through its exported entry point. The CLI then configures its own logger
+  // for the messages it emits itself; it appends rather than truncates so that it does not
+  // clear the file the solver has just opened.
+  const auto log_file    = settings.get_parameter<std::string>(CUOPT_LOG_FILE);
+  const auto log_console = settings.get_parameter<bool>(CUOPT_LOG_TO_CONSOLE);
+
+  cuopt::init_component_logger_t solver_log(log_file, log_console);
+  cuopt::init_logger_t log(log_file, log_console, /*truncate=*/false);
 
   std::string base_filename = file_path.substr(file_path.find_last_of("/\\") + 1);
 

cpp/src/CMakeLists.txt

@@ -4,7 +4,6 @@
 # cmake-format: on
 
 set(UTIL_SRC_FILES ${CMAKE_CURRENT_SOURCE_DIR}/utilities/seed_generator.cu
-                   ${CMAKE_CURRENT_SOURCE_DIR}/utilities/logger.cpp
                    ${CMAKE_CURRENT_SOURCE_DIR}/utilities/version_info.cpp
                    ${CMAKE_CURRENT_SOURCE_DIR}/utilities/timestamp_utils.cpp
                    ${CMAKE_CURRENT_SOURCE_DIR}/utilities/work_unit_scheduler.cpp)

cpp/src/math_optimization/CMakeLists.txt

@@ -9,6 +9,7 @@ list(PREPEND
   ${CMAKE_CURRENT_SOURCE_DIR}/solution_reader.cu
   ${CMAKE_CURRENT_SOURCE_DIR}/solution_writer.cu
   ${CMAKE_CURRENT_SOURCE_DIR}/tic_toc.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/logger_entry.cpp
   )
 
 set(CUOPT_SRC_FILES ${CUOPT_SRC_FILES}

cpp/src/math_optimization/logger_entry.cpp

@@ -0,0 +1,24 @@
+/* clang-format off */
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+/* clang-format on */
+
+#include <utilities/logger.hpp>
+
+/*
+ * The logger itself is header-only and hidden, so it is private to each component library.
+ * This translation unit is compiled into cuopt_mathopt only, which is what makes the
+ * functions below reach mathopt's instance and no other.
+ */
+namespace cuopt::mathematical_optimization {
+
+void configure_logging(const std::string& log_file, bool log_to_console, bool truncate)
+{
+  cuopt::configure_logging_impl(log_file, log_to_console, truncate);
+}
+
+void reset_logging() { cuopt::reset_logging_impl(); }
+
+}  // namespace cuopt::mathematical_optimization

cpp/src/routing/CMakeLists.txt

@@ -1,9 +1,10 @@
 # cmake-format: off
-# SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2024-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 # cmake-format: on
 
 set(ROUTING_SRC_FILES
+  ${CMAKE_CURRENT_SOURCE_DIR}/logger_entry.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/local_search/compute_insertions.cu
   ${CMAKE_CURRENT_SOURCE_DIR}/ges/squeeze.cu
   ${CMAKE_CURRENT_SOURCE_DIR}/local_search/sliding_window.cu

cpp/src/routing/logger_entry.cpp

@@ -0,0 +1,24 @@
+/* clang-format off */
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+/* clang-format on */
+
+#include <utilities/logger.hpp>
+
+/*
+ * The logger itself is header-only and hidden, so it is private to each component library.
+ * This translation unit is compiled into cuopt_routing only, which is what makes the
+ * functions below reach routing's instance and no other.
+ */
+namespace cuopt::routing {
+
+void configure_logging(const std::string& log_file, bool log_to_console, bool truncate)
+{
+  cuopt::configure_logging_impl(log_file, log_to_console, truncate);
+}
+
+void reset_logging() { cuopt::reset_logging_impl(); }
+
+}  // namespace cuopt::routing

cpp/src/routing/solve.cu

@@ -16,6 +16,10 @@ template <typename i_t, typename f_t>
 assignment_t<i_t> solve(data_model_view_t<i_t, f_t> const& data_model,
                         solver_settings_t<i_t, f_t> const& settings)
 {
+  // Routing's logger is private to cuopt_routing and starts out sinking into a buffer, so
+  // without this the CUOPT_LOG_ERROR calls below are recorded and never emitted anywhere.
+  init_logger_t log("", settings.get_error_logging_mode());
+
   try {
     cuopt::routing::solver_t<i_t, f_t> solver(data_model, settings);
     return solver.solve();