feat: Add Mille Solver

.devcontainer/Dockerfile

@@ -1,4 +1,4 @@
-FROM ghcr.io/acts-project/spack-container:24.1.0_linux-ubuntu26.04_gcc-15.2.0_cxx20
+FROM ghcr.io/acts-project/spack-container:24.4.0_linux-ubuntu26.04_gcc-15.2.0_cxx20
 
 RUN apt-get update && apt-get install -y clangd vim
 

.github/actions/dependencies/action.yml

@@ -21,7 +21,7 @@ inputs:
   DEPENDENCY_TAG:
     description: 'Dependency tag to pull from'
     required: false
-    default: 'v24.1.0'
+    default: 'v24.4.0'
   full_install:
     description: 'Whether to do a full dependency installation including Geant4 datasets and Python packages'
     required: false

.github/workflows/builds.yml

@@ -503,7 +503,7 @@ jobs:
           compiler: g++
           flavor: cuda13
           # Flavors need v24.0.0 or newer.
-          DEPENDENCY_TAG: v24.1.0
+          DEPENDENCY_TAG: v24.4.0
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           env_file: .env
 
@@ -624,7 +624,7 @@ jobs:
           compiler: g++
           flavor: cuda13
           # Flavors need v24.0.0 or newer.
-          DEPENDENCY_TAG: v24.1.0
+          DEPENDENCY_TAG: v24.4.0
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           env_file: .env
 
@@ -690,7 +690,7 @@ jobs:
           compiler: g++
           flavor: cuda13
           # Flavors need v24.0.0 or newer.
-          DEPENDENCY_TAG: v24.1.0
+          DEPENDENCY_TAG: v24.4.0
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           env_file: .env
 
@@ -758,7 +758,7 @@ jobs:
           compiler: g++
           flavor: cuda13
           # Flavors need v24.0.0 or newer.
-          DEPENDENCY_TAG: v24.1.0
+          DEPENDENCY_TAG: v24.4.0
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           env_file: .env
 
@@ -832,7 +832,7 @@ jobs:
           compiler: g++
           flavor: cuda13
           # Flavors need v24.0.0 or newer.
-          DEPENDENCY_TAG: v24.1.0
+          DEPENDENCY_TAG: v24.4.0
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           env_file: .env
 

.github/workflows/detray.yml

@@ -145,7 +145,7 @@ jobs:
       with:
         compiler: g++
         # Flavors need v24.0.0 or newer.
-        DEPENDENCY_TAG: v24.1.0
+        DEPENDENCY_TAG: v24.4.0
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         env_file: .env
 
@@ -247,7 +247,7 @@ jobs:
         compiler: g++
         flavor: ${{ matrix.PLATFORM.FLAVOR }}
         # Flavors need v24.0.0 or newer.
-        DEPENDENCY_TAG: v24.1.0
+        DEPENDENCY_TAG: v24.4.0
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         env_file: .env
 
@@ -320,7 +320,7 @@ jobs:
         compiler: g++
         flavor: cuda13
         # Flavors need v24.0.0 or newer.
-        DEPENDENCY_TAG: v24.1.0
+        DEPENDENCY_TAG: v24.4.0
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         env_file: .env
 
@@ -448,7 +448,7 @@ jobs:
       with:
         compiler: g++
         flavor: cuda13
-        DEPENDENCY_TAG: v24.1.0
+        DEPENDENCY_TAG: v24.4.0
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         env_file: .env
 

.github/workflows/traccc.yml

@@ -162,7 +162,7 @@ jobs:
           compiler: ${{ matrix.platform.compiler || 'g++' }}
           flavor: ${{ matrix.platform.flavor }}
           # Flavors need v24.0.0 or newer.
-          DEPENDENCY_TAG: v24.1.0
+          DEPENDENCY_TAG: v24.4.0
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           env_file: .env
 
@@ -287,7 +287,7 @@ jobs:
         with:
           compiler: g++
           flavor: cuda13
-          DEPENDENCY_TAG: v24.1.0
+          DEPENDENCY_TAG: v24.4.0
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           env_file: .env
 

CMakeLists.txt

@@ -338,7 +338,7 @@ set(_acts_doxygen_version 1.9.4)
 set(_acts_hepmc3_version 3.2.4)
 set(_acts_nlohmanjson_version 3.11.3)
 set(_acts_gbl_version 04.00.05)
-set(_acts_mille_version 01.00.05)
+set(_acts_mille_version 01.01.01)
 set(_acts_mp2_version 05.01.05)
 set(_acts_onnxruntime_version 1.12.0)
 set(_acts_geomodel_version 6.8.0)
@@ -363,22 +363,27 @@ include(ActsExternSources)
 if(ACTS_SETUP_BOOST)
     # Enable both program_options and unit_test_framework to reduce complexity
     # Also Cuda tests seem to use program_options
+    set(_acts_boost_components)
     if(
         ACTS_BUILD_ANALYSIS_APPS
         OR ACTS_BUILD_UNITTESTS
         OR ACTS_BUILD_INTEGRATIONTESTS
         OR ACTS_BUILD_BENCHMARKS
     )
-        find_package(
-            Boost
-            ${_acts_boost_version}
-            REQUIRED
-            COMPONENTS program_options unit_test_framework
-        )
-    else()
-        find_package(Boost ${_acts_boost_version} REQUIRED COMPONENTS)
+        list(APPEND _acts_boost_components program_options unit_test_framework)
     endif()
 
+    # Only the Mille plugin needs process/filesystem, and neither is part of
+    # every Boost installation (Boost.Process is a compiled library since Boost
+    # 1.88). The plugin reports if the one it needs is missing.
+    find_package(
+        Boost
+        ${_acts_boost_version}
+        REQUIRED
+        COMPONENTS ${_acts_boost_components}
+        OPTIONAL_COMPONENTS process filesystem
+    )
+
     if(Boost_VERSION VERSION_EQUAL "1.85.0")
         set(_boost_version_severity WARNING)
         if(ACTS_BUILD_EXAMPLES)

Plugins/Mille/CMakeLists.txt

@@ -2,6 +2,9 @@ acts_add_library(
     PluginMille
     src/Helpers.cpp
     src/ActsToMille.cpp
+    src/MillePedeSolver.cpp
+    src/MillePedeError.cpp
+    src/runChildProcess.cpp
     ACTS_INCLUDE_FOLDER include/ActsPlugins
 )
 
@@ -12,6 +15,45 @@ target_include_directories(
         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
 )
 
-target_link_libraries(ActsPluginMille PUBLIC ActsAlignment Mille2)
+# The solver runs `pede` as a child process via Boost.Process: the compiled
+# library from Boost 1.88 on, the header-only v1 API (which builds on
+# Boost.Filesystem) before that. Both are probed as optional components at the
+# top level, since only this plugin needs them.
+if(Boost_VERSION VERSION_GREATER_EQUAL 1.88.0)
+    set(_mille_boost_component process)
+    set(_mille_boost_reason "which is a compiled library since Boost 1.88")
+else()
+    set(_mille_boost_component filesystem)
+    set(_mille_boost_reason "whose pre-1.88 API is built on Boost.Filesystem")
+endif()
+
+if(NOT TARGET Boost::${_mille_boost_component})
+    foreach(_component process filesystem)
+        if(TARGET Boost::${_component})
+            string(APPEND _mille_boost_found " ${_component}")
+        endif()
+    endforeach()
+    if(NOT _mille_boost_found)
+        set(_mille_boost_found " none of them")
+    endif()
+
+    message(
+        FATAL_ERROR
+        "The Mille plugin runs `pede` as a child process via Boost.Process, "
+        "${_mille_boost_reason}, so it needs the Boost "
+        "${_mille_boost_component} library. The Boost ${Boost_VERSION} "
+        "installation in ${Boost_DIR} provides:${_mille_boost_found}. Please "
+        "enable ${_mille_boost_component} in the Boost build (with spack: "
+        "`boost +${_mille_boost_component}`), or set "
+        "ACTS_BUILD_PLUGIN_MILLE=OFF."
+    )
+endif()
+
+# Boost is only used by the solver implementation, not by any public header
+target_link_libraries(
+    ActsPluginMille
+    PUBLIC ActsAlignment Mille2
+    PRIVATE Boost::boost Boost::${_mille_boost_component}
+)
 
 acts_compile_headers(PluginMille GLOB include/**/*.hpp)

Plugins/Mille/include/ActsPlugins/Mille/MillePedeError.hpp

@@ -0,0 +1,39 @@
+// This file is part of the ACTS project.
+//
+// Copyright (C) 2016 CERN for the benefit of the ACTS project
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#pragma once
+
+#include <system_error>
+#include <type_traits>
+
+namespace ActsPlugins::ActsToMille {
+/// Error codes for Millepede run
+/// @ingroup errors
+enum class MillePedeError {
+  InstallationNotFound = 1,  // no valid install found
+  SteeringNotFound = 2,      // steering file not found
+  SolverCrash = 3,           // solver crashed
+  InvalidSolution = 4,       // solver finished but the solution is invalid
+  SolutionNotReadable = 5,   // solution file could not be read
+};
+
+/// @cond
+/// Create error code from MillePedeError
+/// @param e The error code enum value
+/// @return Standard error code
+std::error_code make_error_code(ActsToMille::MillePedeError e);
+/// @endcond
+
+}  // namespace ActsPlugins::ActsToMille
+
+namespace std {
+// register with STL
+template <>
+struct is_error_code_enum<ActsPlugins::ActsToMille::MillePedeError>
+    : std::true_type {};
+}  // namespace std

Plugins/Mille/include/ActsPlugins/Mille/MillePedeSolver.hpp

@@ -0,0 +1,107 @@
+// This file is part of the ACTS project.
+//
+// Copyright (C) 2016 CERN for the benefit of the ACTS project
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#pragma once
+#include "Acts/Utilities/Logger.hpp"
+#include "Acts/Utilities/Result.hpp"
+#include "ActsPlugins/Mille/MillePedeError.hpp"
+
+#include <filesystem>
+#include <vector>
+
+namespace ActsPlugins::ActsToMille {
+
+/// class wrapping an external call to the 'pede' solver
+/// program of the Millepede-II alignment toolkit.
+class MillePedeSolver {
+ public:
+  /// @brief abstract summary of the exit codes returned by pede.
+  enum class mpExitStatus {
+    notFinishedOrCrashed,  /// job is still running or crashed before exiting
+    nominalExit,           /// nominal exit
+    tolerableWarnings,     /// exit with tolerable warnings, considered ok
+    seriousWarnings,       /// exit with serious warnings, should investigate
+    noSolution,            /// exit without solution (usually: rank deficit)
+    aborted                /// aborted due to errors
+  };
+
+  /// @brief configuration for running pede.
+  /// Currently, most details are delegated to the steering file syntax.
+  struct Config {
+    std::string steeringFile =
+        "pedeSteerMaster.txt";                /// steering file with run options
+    std::filesystem::path workDir = "";       /// directory to run in
+    std::vector<std::string> extraOpts = {};  /// extra CLI options
+    std::string resFileName =
+        "";  /// destination for result file - if empty, keep original
+    std::string redirectStdout = "";  /// destination for the cout/cerr printout
+                                      /// from pede - if empty, send to parent
+    std::string logFileName =
+        "";  /// destination for the log file - if empty, keep original
+    std::string histoFileName =
+        "";  /// destination for the histogram file - if empty, keep original
+    std::string evFileName =
+        "";  /// destination for the eigenvector file - if empty, keep original
+  };
+
+  /// @brief package the result of the alignment fit
+  struct mpResult {
+    int exitCode = -1;  /// raw pede exit code
+    mpExitStatus exitStatus =
+        mpExitStatus::notFinishedOrCrashed;  /// summary exit status
+    std::string exitMessage = "";            /// detailed exit message
+    std::filesystem::path resultsFile;  /// file containing parameter results
+    std::filesystem::path logFile;      /// log file
+    std::filesystem::path histoFile;    /// file with validation histograms
+    std::filesystem::path evFile;       /// file with eigenvectors
+  };
+
+  /// @brief constructor - nothing to do as minimal internal state carried
+  explicit MillePedeSolver(Acts::Logging::Level level = Acts::Logging::INFO)
+      : m_logger(Acts::getDefaultLogger("MillePedeSolver", level)) {}
+
+  /// @brief Runs the solving.
+  /// Can take some time for large fits.
+  /// Will invoke pede, await the exit, and parse
+  /// the output.
+  /// @param cfg: The configuration to use
+  Acts::Result<mpResult> solve(Config cfg) const;
+
+ private:
+  /// @brief translation of the detailed pede code to a summary status
+  /// Will translate the range of ~30 possible MP exit codes to a simplified
+  /// enum value that gives a high-level summary of the status.
+  /// @param theExitCode: The integer exit code found in the millepede.end file
+  static mpExitStatus interpretExit(int theExitCode);
+
+  /// @brief Reads the `millepede.end` file and parses its content
+  /// @param mpend: The file to read, assumed that the user has checked for existence before
+  /// @return a tuple containing the original integer exit code, a simplified exit status enum,
+  /// and the additional status message emitted by pede.
+  std::tuple<int, mpExitStatus, std::string> readDetailedExit(
+      const std::filesystem::path& mpend) const;
+
+  /// @brief Utility method to check if an output exists, copy it if the user requested a relocation,
+  /// and returns the final resolved output location, which will be:
+  /// - if the output does not exist: empty path
+  /// - if the output does exist and was not relocated: original location
+  /// - if the output does exist, and was relocated: user-specified location
+  /// - if the output does exist, was requested for relocation but the copy
+  /// failed: original location
+  /// @param originalLoc: Original expected location of the file
+  /// @param userLoc: Desired final location of the file. If empty, no copy will be made.
+  std::filesystem::path copyIfRequested(
+      const std::filesystem::path& originalLoc,
+      const std::filesystem::path& userLoc) const;
+
+  std::unique_ptr<const Acts::Logger> m_logger;  /// logger
+
+  /// Private access to the logger
+  const Acts::Logger& logger() const { return *m_logger; }
+};
+}  // namespace ActsPlugins::ActsToMille