CQMP · egull · Sep 26, 2026 · Sep 24, 2026 · Sep 24, 2026 · Sep 24, 2026
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
@@ -0,0 +1,214 @@
+name: Maxent CI
+
+on:
+  push:
+    branches:
+      - master
+      - modernize/step2
+  pull_request:
+    branches:
+      - master
+      - modernize/step2
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+env:
+  BOOST_VERSION: "1.91.0"
+  BOOST_VERSION_U: "1_91_0"
+
+jobs:
+  linux-build:
+    name: >-
+      Maxent / ${{ matrix.plat.os }} / ${{ matrix.plat.c_compiler }}-${{ matrix.plat.c_version }} /
+      ${{ matrix.plat.variant }}
+    runs-on: ${{ matrix.plat.os }}
+    timeout-minutes: 90
+    strategy:
+      fail-fast: false
+      matrix:
+        plat:
+          # Match the compiler installation conventions used by ALPS 3.0 CI.
+          - { os: ubuntu-22.04, comp_pack: "gcc-11 g++-11", c_compiler: gcc, cxx_compiler: g++, c_version: 11, variant: strict }
+          - { os: ubuntu-24.04, comp_pack: "gcc-13 g++-13", c_compiler: gcc, cxx_compiler: g++, c_version: 13, variant: strict }
+          - { os: ubuntu-24.04, comp_pack: "gcc-15 g++-15", c_compiler: gcc, cxx_compiler: g++, c_version: 15, variant: strict }
+          - { os: ubuntu-22.04, comp_pack: "clang-15", c_compiler: clang, cxx_compiler: clang++, c_version: 15, variant: strict }
+          - { os: ubuntu-24.04, comp_pack: "clang-19", c_compiler: clang, cxx_compiler: clang++, c_version: 19, variant: strict }
+          - { os: ubuntu-24.04, comp_pack: "gcc-13 g++-13", c_compiler: gcc, cxx_compiler: g++, c_version: 13, variant: lapack, lapack: true }
+          - { os: ubuntu-24.04, comp_pack: "clang-19", c_compiler: clang, cxx_compiler: clang++, c_version: 19, variant: asan-ubsan, sanitizers: true }
+          - { os: ubuntu-24.04, comp_pack: "gcc-13 g++-13", c_compiler: gcc, cxx_compiler: g++, c_version: 13, variant: alps-flags, alps_flags: true }
+
+    steps:
+      - uses: actions/checkout@v7
+      - name: Check out ALPSCore
+        uses: actions/checkout@v7
+        with:
+          repository: ALPSCore/ALPSCore
+          path: alpscore
+      - name: Set up Python
+        uses: actions/setup-python@v7
+        with:
+          python-version: "3.14"
+      - name: Install dependencies
+        timeout-minutes: 20
+        run: |
+          printf 'Acquire::Retries "3";\nAcquire::http::Timeout "30";\nAcquire::https::Timeout "30";\n' \
+            | sudo tee /etc/apt/apt.conf.d/99ci-timeouts > /dev/null
+          sudo apt-get update
+          sudo apt-get install -y liblapack-dev libblas-dev libopenmpi-dev libhdf5-serial-dev libeigen3-dev
+          if [[ "${{ matrix.plat.c_compiler }}" == "clang" && "${{ matrix.plat.c_version }}" -ge 19 ]]; then
+            wget -nv --tries=3 --timeout=60 -O /tmp/llvm.sh https://apt.llvm.org/llvm.sh
+            sudo bash /tmp/llvm.sh "${{ matrix.plat.c_version }}" all
+          else
+            if [[ "${{ matrix.plat.c_compiler }}" == "gcc" && "${{ matrix.plat.c_version }}" -ge 15 ]]; then
+              sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+              sudo apt-get update
+            fi
+            sudo apt-get install -y ${{ matrix.plat.comp_pack }}
+          fi
+          python -m pip install --upgrade pip
+          python -m pip install "numpy>=1.26" "h5py>=3.10"
+      - name: Determine dependency cache identity
+        id: dependency-cache
+        run: |
+          {
+            "${{ matrix.plat.cxx_compiler }}-${{ matrix.plat.c_version }}" --version
+            dpkg-query -W -f='${Package}=${Version}\n' \
+              libhdf5-serial-dev libeigen3-dev libopenmpi-dev
+          } > "${RUNNER_TEMP}/dependency-versions.txt"
+          dependency_key=$(sha256sum "${RUNNER_TEMP}/dependency-versions.txt" | cut -d ' ' -f 1)
+          echo "key=${dependency_key}" >> "${GITHUB_OUTPUT}"
+      - name: Cache Boost and ALPSCore
+        id: cache-dependencies
+        uses: actions/cache@v6
+        with:
+          path: |
+            ${{ runner.temp }}/boost
+            ${{ runner.temp }}/alpscore-install
+          key: maxent-deps-${{ runner.os }}-${{ runner.arch }}-${{ steps.dependency-cache.outputs.key }}-boost-${{ env.BOOST_VERSION }}-${{ hashFiles('alpscore/**') }}
+      - name: Build Boost and ALPSCore
+        if: steps.cache-dependencies.outputs.cache-hit != 'true'
+        env:
+          CC: ${{ matrix.plat.c_compiler }}-${{ matrix.plat.c_version }}
+          CXX: ${{ matrix.plat.cxx_compiler }}-${{ matrix.plat.c_version }}
+        run: |
+          wget -nv --tries=3 --timeout=60 --waitretry=10 \
+            "https://archives.boost.io/release/${BOOST_VERSION}/source/boost_${BOOST_VERSION_U}.tar.gz"
+          tar -xzf "boost_${BOOST_VERSION_U}.tar.gz"
+          cd "boost_${BOOST_VERSION_U}"
+          ./bootstrap.sh --prefix="${RUNNER_TEMP}/boost" --with-libraries=program_options
+          ./b2 -j 2 install
+          cd ..
+          cmake -S alpscore -B alpscore-build \
+            -DTesting=OFF \
+            -DALPS_CXX_STD=c++17 \
+            -DBoost_ROOT="${RUNNER_TEMP}/boost" \
+            -DCMAKE_PREFIX_PATH="${RUNNER_TEMP}/boost" \
+            -DCMAKE_INSTALL_PREFIX="${RUNNER_TEMP}/alpscore-install"
+          cmake --build alpscore-build -j 2
+          cmake --install alpscore-build
+      - name: Configure Maxent
+        env:
+          CC: ${{ matrix.plat.c_compiler }}-${{ matrix.plat.c_version }}
+          CXX: ${{ matrix.plat.cxx_compiler }}-${{ matrix.plat.c_version }}
+        run: |
+          extra_flags=""
+          if [[ "${{ matrix.plat.sanitizers || false }}" == "true" ]]; then
+            extra_flags="-fsanitize=address,undefined -fno-omit-frame-pointer"
+          elif [[ "${{ matrix.plat.alps_flags || false }}" == "true" ]]; then
+            extra_flags="-fpermissive -DBOOST_NO_AUTO_PTR -DBOOST_FILESYSTEM_NO_CXX20_ATOMIC_REF -DBOOST_TIMER_ENABLE_DEPRECATED"
+          fi
+          cmake -S . -B build/ci \
+            -DCMAKE_BUILD_TYPE=${{ matrix.plat.sanitizers && 'Debug' || 'Release' }} \
+            -DCMAKE_PREFIX_PATH="${RUNNER_TEMP}/alpscore-install;${RUNNER_TEMP}/boost" \
+            -DALPSCore_DIR="${RUNNER_TEMP}/alpscore-install/share/ALPSCore" \
+            -DBoost_ROOT="${RUNNER_TEMP}/boost" \
+            -DMAXENT_USE_LAPACK=${{ matrix.plat.lapack && 'ON' || 'OFF' }} \
+            -DMAXENT_WERROR=ON \
+            -DCMAKE_CXX_FLAGS="${extra_flags}" \
+            -DCMAKE_EXE_LINKER_FLAGS="${extra_flags}"
+      - name: Build Maxent
+        run: cmake --build build/ci -j 2
+      - name: Test Maxent
+        env:
+          ASAN_OPTIONS: detect_leaks=1
+          UBSAN_OPTIONS: print_stacktrace=1
+        run: ctest --test-dir build/ci --output-on-failure
+      - name: Upload test logs on failure
+        if: failure()
+        uses: actions/upload-artifact@v7
+        with:
+          name: test-logs-${{ matrix.plat.c_compiler }}-${{ matrix.plat.c_version }}-${{ matrix.plat.variant }}
+          path: build/ci/Testing/Temporary/**
+
+  macos-build:
+    name: Maxent / macos-15 / AppleClang / strict
+    runs-on: macos-15
+    timeout-minutes: 90
+    steps:
+      - uses: actions/checkout@v7
+      - name: Check out ALPSCore
+        uses: actions/checkout@v7
+        with:
+          repository: ALPSCore/ALPSCore
+          path: alpscore
+      - name: Set up Python
+        uses: actions/setup-python@v7
+        with:
+          python-version: "3.14"
+      - name: Install dependencies
+        timeout-minutes: 30
+        run: |
+          brew install boost eigen hdf5 open-mpi
+          python -m pip install --upgrade pip
+          python -m pip install "numpy>=1.26" "h5py>=3.10"
+      - name: Determine dependency cache identity
+        id: dependency-cache
+        run: |
+          {
+            /usr/bin/clang --version
+            brew list --versions boost eigen hdf5 open-mpi
+          } > "${RUNNER_TEMP}/dependency-versions.txt"
+          dependency_key=$(shasum -a 256 "${RUNNER_TEMP}/dependency-versions.txt" | cut -d ' ' -f 1)
+          echo "key=${dependency_key}" >> "${GITHUB_OUTPUT}"
+      - name: Cache ALPSCore
+        id: cache-alpscore
+        uses: actions/cache@v6
+        with:
+          path: ${{ runner.temp }}/alpscore-install
+          key: maxent-alpscore-${{ runner.os }}-${{ runner.arch }}-${{ steps.dependency-cache.outputs.key }}-${{ hashFiles('alpscore/**') }}
+      - name: Build ALPSCore
+        if: steps.cache-alpscore.outputs.cache-hit != 'true'
+        env:
+          CC: /usr/bin/clang
+          CXX: /usr/bin/clang++
+        run: |
+          cmake -S alpscore -B alpscore-build \
+            -DTesting=OFF \
+            -DALPS_CXX_STD=c++17 \
+            -DCMAKE_PREFIX_PATH="$(brew --prefix)" \
+            -DEIGEN3_INCLUDE_DIR="$(brew --prefix eigen)/include/eigen3" \
+            -DCMAKE_INSTALL_PREFIX="${RUNNER_TEMP}/alpscore-install"
+          cmake --build alpscore-build -j "$(sysctl -n hw.ncpu)"
+          cmake --install alpscore-build
+      - name: Configure Maxent
+        env:
+          CC: /usr/bin/clang
+          CXX: /usr/bin/clang++
+        run: |
+          cmake -S . -B build/ci \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DCMAKE_PREFIX_PATH="${RUNNER_TEMP}/alpscore-install;$(brew --prefix)" \
+            -DALPSCore_DIR="${RUNNER_TEMP}/alpscore-install/share/ALPSCore" \
+            -DMAXENT_WERROR=ON
+      - name: Build Maxent
+        run: cmake --build build/ci -j "$(sysctl -n hw.ncpu)"
+      - name: Test Maxent
+        run: ctest --test-dir build/ci --output-on-failure
+      - name: Upload test logs on failure
+        if: failure()
+        uses: actions/upload-artifact@v7
+        with:
+          name: test-logs-macos-15-appleclang
+          path: build/ci/Testing/Temporary/**
diff --git a/.travis.yml b/.travis.yml
diff --git a/ALPS3_MIGRATION_PLAN.md b/ALPS3_MIGRATION_PLAN.md
@@ -436,7 +436,8 @@ Keep the `MaxEntSimulation` public getters stable, because the tests use them.
 
 ### 2.4 Hygiene and CI
 
-* Delete `.travis.yml` and add GitHub Actions with this matrix:
+* **In progress 2026-09-24:** delete `.travis.yml` and add GitHub Actions,
+  mirroring ALPS 3.0's workflow conventions, with this matrix:
   * Ubuntu: GCC 11/13/15, Clang 15/19
   * macOS arm64: AppleClang
   * one ASan/UBSan job
@@ -445,7 +446,8 @@ Keep the `MaxEntSimulation` public getters stable, because the tests use them.
   Build ALPSCore from source in CI and cache it.
 * **Replace the allowlist `.gitignore`.** Done 2026-09-23: replaced with a minimal ignore list (build dirs, OS/editor files, Python caches). Local-only material (D10) is hidden per clone via `.git/info/exclude`, not in the repository.
 * ~~Remove the dead Pade sources~~ Done: Pade was removed entirely (D7).
-* Update the README: build instructions, dependency list (no GSL), and remove the Travis badge.
+* **Done 2026-09-24:** update the README build/test instructions and dependency
+  list, and replace the Travis badge with the GitHub Actions badge.
 
 ### 2.5 Isolate ALPSCore behind two seams (bridge into step 4)
 

diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -39,7 +39,10 @@ if(NOT Boost_FOUND)
   message(FATAL_ERROR "Boost ${ALPSCore_BOOST_VERSION} (the version ALPSCore was built with) was not "
     "found. Pass -DBoost_DIR=<dir containing BoostConfig.cmake> or add its prefix to CMAKE_PREFIX_PATH.")
 endif()
-find_package(Eigen3 3.3 CONFIG REQUIRED)
+find_package(Eigen3 CONFIG REQUIRED)
+if(Eigen3_VERSION VERSION_LESS 3.3)
+  message(FATAL_ERROR "Eigen 3.3 or newer is required (found ${Eigen3_VERSION})")
+endif()
 
 set(HAVE_BLAS 0)
 set(HAVE_LAPACK 0)
@@ -55,7 +58,11 @@ configure_file(cmake/maxent_config.hpp.in ${PROJECT_BINARY_DIR}/config/maxent_co
 add_library(maxent_warnings INTERFACE)
 target_compile_options(maxent_warnings INTERFACE
   $<$<CXX_COMPILER_ID:GNU,Clang,AppleClang>:-Wall -Wextra -Wpedantic>
-  $<$<AND:$<BOOL:${MAXENT_WERROR}>,$<CXX_COMPILER_ID:GNU,Clang,AppleClang>>:-Werror>)
+  $<$<AND:$<BOOL:${MAXENT_WERROR}>,$<CXX_COMPILER_ID:GNU,Clang,AppleClang>>:-Werror>
+  # GCC diagnoses Boost.Variant's type-erased storage as maybe-uninitialized
+  # when ALPS parameters are instantiated. Keep the warning visible without
+  # treating this third-party false positive as a Maxent build failure.
+  $<$<AND:$<BOOL:${MAXENT_WERROR}>,$<CXX_COMPILER_ID:GNU>>:-Wno-error=maybe-uninitialized>)
 
 # ---------------------------------------------------------------- library and program
 add_library(maxent_core STATIC

diff --git a/README.md b/README.md
@@ -1,6 +1,6 @@
 Maxent
 ======
-[![Build Status](https://travis-ci.org/CQMP/Maxent.svg?branch=master)](https://travis-ci.org/CQMP/Maxent)
+[![CI](https://github.com/CQMP/Maxent/actions/workflows/build.yml/badge.svg)](https://github.com/CQMP/Maxent/actions/workflows/build.yml)
 [![License: MIT](https://img.shields.io/badge/license-MIT-blue.svg)](LICENSE.txt)
 
 The Maxent Project: A utility for performing analytic continuation using the method of Maximum Entropy.
@@ -38,10 +38,15 @@ Table of Contents
 ### Libraries
 
 #### Boost
-When compiling both ALPSCore and Maxent, be careful to ensure boost was compiled with the same library and stdlib as ALPSCore and Maxent.   
+Maxent uses Boost headers and the `program_options` library in its utilities.
+Use the same Boost version and C++ standard library that were used to build
+ALPSCore; CMake checks the version reported by ALPSCore.
 
 #### ALPSCore
-ALPSCore needs to be properly installed, see [ALPSCore library](https://github.com/ALPSCore/ALPSCore). ALPSCore provides the location of the Boost libraries.
+ALPSCore must be installed, including its CMake package files; see the
+[ALPSCore library](https://github.com/ALPSCore/ALPSCore). Set `ALPSCore_DIR`
+to the directory containing `ALPSCoreConfig.cmake` when it is not found
+automatically.
 
 #### Eigen3
 For our linear algebra routines we use Eigen3 version >=3.3. CMake finds it through its `Eigen3Config.cmake`; if it is not in a standard location, add its prefix to `CMAKE_PREFIX_PATH` or set `-DEigen3_DIR=/path/to/share/eigen3/cmake`.
@@ -80,7 +85,8 @@ Options:
 | `MAXENT_USE_SYSTEM_GTEST` | OFF | use an installed GoogleTest instead of downloading 1.18.0 |
 
 ### Tests
-Once compiled, run `ctest --test-dir build` (or `ctest --preset <preset>` for
+Once compiled, run `ctest --test-dir build --output-on-failure` (or
+`ctest --preset <preset>` for
 a preset build) to make sure everything works. This runs the unit tests (label
 `unit`) and the regression suite (label `regression-fast`, needs Python 3 with
 numpy and h5py); see [test/regression/README.md](test/regression/README.md).

diff --git a/src/default_model.cpp b/src/default_model.cpp
@@ -113,8 +113,11 @@ double GeneralDefaultModel::norm() {
   //this is an evaluation on an equidistant grid; sum integrated by trapezoidal rule
   double delta_omega = (omega_max - omega_min) / (ntab - 1);
   for (int o = 1; o < ntab; ++o) {
-    double omega1 = omega_min + (o - 1) * delta_omega;
-    double omega2 = omega_min + o * delta_omega;
+    // This weighted-endpoint form gives an exact zero on symmetric grids.
+    // That matters for models with a deliberately discontinuous zero branch
+    // and avoids compiler-dependent FMA rounding at the branch point.
+    double omega1 = ((ntab - o) * omega_min + (o - 1) * omega_max) / (ntab - 1);
+    double omega2 = ((ntab - 1 - o) * omega_min + o * omega_max) / (ntab - 1);
     sum += ((*Mod)(omega1) + (*Mod)(omega2)) / 2. * delta_omega;
     xtab[o] = sum;
   }
@@ -191,4 +194,3 @@ std::shared_ptr<DefaultModel> make_default_model(const alps::params& parms, std:
 }
 
 
-
diff --git a/src/maxent.cpp b/src/maxent.cpp
@@ -12,6 +12,7 @@
 #include "maxent.hpp"
 #include <alps/utilities/fs/remove_extensions.hpp>
 
+#include <iomanip>
 
 int main(int argc,const char** argv)
 {