diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 1ae6f134..28778215 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -17,12 +17,14 @@ jobs:
     strategy:
       matrix:
         DISTRO: [
+          { "ubuntu": "noble", "suffix": "gcc" },
+          { "ubuntu": "noble", "suffix": "llvm" },
           { "ubuntu": "jammy", "suffix": "gcc" },
           { "ubuntu": "jammy", "suffix": "llvm" },
           { "ubuntu": "jammy_cuda12.2", "suffix": "gcc.cuda" },
           { "ubuntu": "jammy_cuda12.2", "suffix": "llvm.cuda" },
-          { "ubuntu": "noble", "suffix": "gcc" },
-          { "ubuntu": "noble", "suffix": "llvm" }
+          { "ubuntu": "focal", "suffix": "focal" },
+          { "ubuntu": "focal_cuda12.2", "suffix": "focal.cuda" },
         ]
 
     steps:
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c86f6dda..2b8b6621 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,7 +29,7 @@ find_package(GTSAM REQUIRED)
 find_package(OpenMP REQUIRED)
 find_package(Eigen3 REQUIRED)
 
-if(${BUILD_WITH_CUDA} AND ${EIGEN3_VERSION_STRING} VERSION_LESS "3.3.90")
+if(${BUILD_WITH_CUDA} AND ${EIGEN3_VERSION_STRING} AND ${EIGEN3_VERSION_STRING} VERSION_LESS "3.3.90")
   message(WARNING "Detected Eigen ${EIGEN3_VERSION_STRING} is not compatible with CUDA")
   message(WARNING "Use Eigen 3.3.90 or later (3.4.0 is recommended)")
 endif()
diff --git a/docker/ubuntu/Dockerfile.focal b/docker/ubuntu/Dockerfile.focal
new file mode 100644
index 00000000..1b92be9b
--- /dev/null
+++ b/docker/ubuntu/Dockerfile.focal
@@ -0,0 +1,28 @@
+ARG BASE_IMAGE=koide3/gtsam_docker:focal
+
+FROM ${BASE_IMAGE}
+
+RUN test -f /usr/share/doc/kitware-archive-keyring/copyright || wget -O - https://apt.kitware.com/keys/kitware-archive-latest.asc 2>/dev/null | gpg --dearmor - | tee /usr/share/keyrings/kitware-archive-keyring.gpg >/dev/null 
+RUN echo 'deb [signed-by=/usr/share/keyrings/kitware-archive-keyring.gpg] https://apt.kitware.com/ubuntu/ focal main' | tee /etc/apt/sources.list.d/kitware.list >/dev/null
+RUN echo 'deb [signed-by=/usr/share/keyrings/kitware-archive-keyring.gpg] https://apt.kitware.com/ubuntu/ focal-rc main' | tee -a /etc/apt/sources.list.d/kitware.list >/dev/null
+
+RUN apt-get update \
+  && apt-get upgrade -y \
+  && apt-fast clean \
+  && rm -rf /var/lib/apt/lists/*
+
+COPY . /root/gtsam_points
+WORKDIR /root/gtsam_points/build
+RUN rm -rf *
+RUN cmake .. \
+  -DBUILD_DEMO=ON \
+  -DBUILD_TESTS=ON \
+  -DBUILD_EXAMPLE=ON \
+  -DBUILD_WITH_CUDA=OFF \
+  -DCMAKE_BUILD_TYPE=Release && \
+  make -j$(nproc) && \
+  make test && \
+  make install && \
+  rm -rf /root/gtsam_points/build
+
+CMD ["bash"]
diff --git a/docker/ubuntu/Dockerfile.focal.cuda b/docker/ubuntu/Dockerfile.focal.cuda
new file mode 100644
index 00000000..90acd3af
--- /dev/null
+++ b/docker/ubuntu/Dockerfile.focal.cuda
@@ -0,0 +1,36 @@
+ARG BASE_IMAGE=koide3/gtsam_docker:focal_cuda12.2
+
+FROM ${BASE_IMAGE}
+
+RUN test -f /usr/share/doc/kitware-archive-keyring/copyright || wget -O - https://apt.kitware.com/keys/kitware-archive-latest.asc 2>/dev/null | gpg --dearmor - | tee /usr/share/keyrings/kitware-archive-keyring.gpg >/dev/null 
+RUN echo 'deb [signed-by=/usr/share/keyrings/kitware-archive-keyring.gpg] https://apt.kitware.com/ubuntu/ focal main' | tee /etc/apt/sources.list.d/kitware.list >/dev/null
+RUN echo 'deb [signed-by=/usr/share/keyrings/kitware-archive-keyring.gpg] https://apt.kitware.com/ubuntu/ focal-rc main' | tee -a /etc/apt/sources.list.d/kitware.list >/dev/null
+
+RUN apt-get update \
+  && apt-get upgrade -y \
+  && apt-fast clean \
+  && rm -rf /var/lib/apt/lists/*
+
+# System eigen on focal is too old.
+# Install Eigen that is newer but compatible with 3.3.7 used by GTSAM.
+RUN git clone https://gitlab.com/libeigen/eigen.git
+WORKDIR /root/eigen
+RUN git checkout 1fd5ce1
+WORKDIR /root/eigen/build
+RUN cmake .. && make install
+
+COPY . /root/gtsam_points
+WORKDIR /root/gtsam_points/build
+RUN rm -rf *
+RUN cmake .. \
+  -DBUILD_DEMO=ON \
+  -DBUILD_TESTS=ON \
+  -DBUILD_EXAMPLE=ON \
+  -DBUILD_WITH_CUDA=ON \
+  -DBUILD_WITH_CUDA_MULTIARCH=ON \
+  -DCMAKE_BUILD_TYPE=Release && \
+  make -j$(nproc) && \
+  make install && \
+  rm -rf /root/gtsam_points/build
+
+CMD ["bash"]
diff --git a/docker/ubuntu/Dockerfile.gcc.cuda b/docker/ubuntu/Dockerfile.gcc.cuda
index c7d099e5..0bdc587d 100644
--- a/docker/ubuntu/Dockerfile.gcc.cuda
+++ b/docker/ubuntu/Dockerfile.gcc.cuda
@@ -1,4 +1,4 @@
-ARG BASE_IMAGE=koide3/gtsam_docker:jammy
+ARG BASE_IMAGE=koide3/gtsam_docker:jammy_cuda12.2
 
 FROM ${BASE_IMAGE}
 
diff --git a/docker/ubuntu/Dockerfile.llvm.cuda b/docker/ubuntu/Dockerfile.llvm.cuda
index 5d4b8f16..1e220754 100644
--- a/docker/ubuntu/Dockerfile.llvm.cuda
+++ b/docker/ubuntu/Dockerfile.llvm.cuda
@@ -1,4 +1,4 @@
-ARG BASE_IMAGE=koide3/gtsam_docker:jammy
+ARG BASE_IMAGE=koide3/gtsam_docker:jammy_cuda12.2
 
 FROM ${BASE_IMAGE}
 
diff --git a/include/gtsam_points/ann/small_kdtree.hpp b/include/gtsam_points/ann/small_kdtree.hpp
index 8fa409da..55d46990 100644
--- a/include/gtsam_points/ann/small_kdtree.hpp
+++ b/include/gtsam_points/ann/small_kdtree.hpp
@@ -39,6 +39,7 @@
  *************************************************************************/
 #pragma once
 
+#include <atomic>
 #include <memory>
 #include <numeric>
 #include <Eigen/Core>