Refactor: Replace RapidJSON with nlohmann-json

.github/workflows/build_test_cmake.yml

@@ -24,11 +24,11 @@ jobs:
 
           - tag: gnu
             external_toolchain_args: ""
-            build_args: "-DENABLE_LIBXC=ON -DENABLE_MLALGO=ON -DENABLE_LIBRI=ON -DENABLE_DFTD4=ON -DENABLE_PEXSI=ON"
+            build_args: "-DENABLE_LIBXC=ON -DENABLE_MLALGO=ON -DENABLE_LIBRI=ON -DENABLE_DFTD4=ON -DENABLE_PEXSI=ON -DENABLE_JSON=ON"
             name: "Build extra components with GNU toolchain"
           - tag: intel
             external_toolchain_args: "--with-intel"
-            build_args: "-DENABLE_LIBXC=ON -DENABLE_MLALGO=ON -DENABLE_LIBRI=ON -DENABLE_DFTD4=ON"
+            build_args: "-DENABLE_LIBXC=ON -DENABLE_MLALGO=ON -DENABLE_LIBRI=ON -DENABLE_DFTD4=ON -DENABLE_JSON=ON"
             name: "Build extra components with Intel toolchain"
 
           - tag: cuda

.github/workflows/build_test_makefile.yml

@@ -22,7 +22,9 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v7.0.1
       - name: Build
+        # TODO: Remove nlohmann-json installation here since Dockerfile will have installed it.
         run: |
+          apt update && apt install -y nlohmann-json3-dev
           export I_MPI_CXX=icpx
           chmod a+x generate_build_info.sh
           cd source

.github/workflows/coverage.yml

@@ -63,7 +63,7 @@ jobs:
           -DENABLE_LIBXC=ON \
           -DENABLE_LIBRI=ON \
           -DENABLE_GOOGLEBENCH=ON \
-          -DENABLE_RAPIDJSON=ON \
+          -DENABLE_JSON=ON \
           -DCMAKE_BUILD_TYPE=Debug \
           -DCMAKE_CXX_FLAGS="--coverage -fprofile-arcs -ftest-coverage" \
           -DCMAKE_EXE_LINKER_FLAGS="--coverage"

.github/workflows/test.yml

@@ -93,7 +93,7 @@ jobs:
             -DENABLE_LIBXC=ON \
             -DENABLE_LIBRI=ON \
             -DENABLE_GOOGLEBENCH=ON \
-            -DENABLE_RAPIDJSON=ON \
+            -DENABLE_JSON=ON \
             -DENABLE_FLOAT_FFTW=ON \
             -DENABLE_DFTD4=ON \
             -DENABLE_PEXSI=ON \

CMakeLists.txt

@@ -61,7 +61,7 @@ option(ENABLE_NATIVE_OPTIMIZATION
 
 option(COMMIT_INFO "Print commit information in log" ON)
 option(ENABLE_GOOGLEBENCH "Enable GOOGLE-benchmark usage" OFF)
-option(ENABLE_RAPIDJSON "Enable rapid-json usage" OFF)
+option(ENABLE_JSON "Enable JSON output" OFF)
 option(ENABLE_CNPY "Enable cnpy usage" OFF)
 
 # Options requiring MPI and LCAO
@@ -110,6 +110,14 @@ abacus_rename_option(USE_OPENMP ENABLE_OPENMP)
 abacus_rename_option(USE_ABACUS_LIBM ENABLE_ABACUS_LIBM)
 abacus_rename_option(INFO MATH_INFO)
 
+if(DEFINED CACHE{ENABLE_RAPIDJSON})
+  message(
+    FATAL_ERROR
+      "ENABLE_RAPIDJSON is no longer supported. "
+      "ABACUS now uses nlohmann-json as its JSON backend; "
+      "please use -DENABLE_JSON=ON instead.")
+endif()
+
 if(DEFINED CACHE{ENABLE_LIBCOMM})
   message(
     DEPRECATION
@@ -139,15 +147,8 @@ if(NOT DEFINED NVHPC_ROOT_DIR AND DEFINED ENV{NVHPC_ROOT})
 endif()
 
 # enable json support
-if(ENABLE_RAPIDJSON)
-  find_package(RapidJSON CONFIG REQUIRED)
-  if(NOT TARGET RapidJSON)
-    message(
-      FATAL_ERROR
-      "RapidJSON was found, but target RapidJSON is missing. "
-      "Check if your RapidJSON installation provides a complete exported CMake configuration."
-    )
-  endif()
+if(ENABLE_JSON)
+  find_package(nlohmann_json REQUIRED)
 endif()
 
 # get commit info
@@ -284,8 +285,8 @@ if(CCACHE)
   set(CMAKE_CUDA_COMPILER_LAUNCHER ${CCACHE} ${CMAKE_CUDA_COMPILER_LAUNCHER})
 endif()
 
-# Choose build type from: Debug Release RelWithDebInfo MinSizeRel Select
-# 'Release' configuration for best performance; this will disable all
+# Choose build type from: Debug Release RelWithDebInfo MinSizeRel
+# Select 'Release' configuration for best performance; this will disable all
 # assertions. Other default configurations are also available, see:
 # https://cmake.org/cmake/help/latest/manual/cmake-buildsystem.7.html#default-and-custom-configurations
 # For default flags, see:

Dockerfile.cuda

@@ -2,7 +2,7 @@ FROM nvidia/cuda:12.2.0-devel-ubuntu22.04
 
 RUN apt update && apt install -y --no-install-recommends \
     libopenblas-openmp-dev liblapack-dev libscalapack-mpi-dev libfftw3-dev libcereal-dev \
-    libxc-dev libgtest-dev libgmock-dev libbenchmark-dev python3-numpy ca-certificates \
+    libxc-dev libgtest-dev libgmock-dev libbenchmark-dev python3-numpy ca-certificates nlohmann-json3-dev \
     bc cmake git g++ make time sudo unzip vim wget libopenmpi-dev gfortran libtool-bin && \
     rm -rf /var/lib/apt/lists/*
 
@@ -25,19 +25,11 @@ RUN cd /tmp && \
     ln -s /usr/local/include/elpa_openmp-$ELPA_VER/elpa /usr/local/include/ && \
     cd /tmp && rm -rf elpa-$ELPA_VER
 
-# RapidJSON
-RUN cd /tmp && \
-    wget --quiet https://codeload.github.com/Tencent/rapidjson/tar.gz/24b5e7a -O rapidjson-24b5e7a.tar.gz && \
-    tar -xzf rapidjson-24b5e7a.tar.gz && cd rapidjson-24b5e7a && \
-    cmake -B build -DRAPIDJSON_BUILD_DOC=OFF -DRAPIDJSON_BUILD_EXAMPLES=OFF -DRAPIDJSON_BUILD_TESTS=OFF && \
-    cmake --build build --target install && \
-    cd /tmp && rm -rf rapidjson-24b5e7a rapidjson-24b5e7a.tar.gz
-
 ADD https://api.github.com/repos/deepmodeling/abacus-develop/git/refs/heads/develop /dev/null
 
 RUN git clone https://github.com/deepmodeling/abacus-develop.git --depth 1 && \
     cd abacus-develop && \
-    cmake -B build -DUSE_CUDA=ON -DENABLE_RAPIDJSON=ON && \
+    cmake -B build -DUSE_CUDA=ON -DENABLE_JSON=ON && \
     cmake --build build -j $(nproc) && \
     cmake --install build && \
     rm -rf build && \

Dockerfile.gnu

@@ -10,7 +10,7 @@
 FROM ubuntu:22.04
 RUN apt update && apt install -y --no-install-recommends \
     libopenblas-openmp-dev liblapack-dev libscalapack-mpi-dev libelpa-dev libfftw3-dev libcereal-dev \
-    libxc-dev libgtest-dev libgmock-dev libbenchmark-dev python3-numpy \
+    libxc-dev libgtest-dev libgmock-dev libbenchmark-dev python3-numpy nlohmann-json3-dev \
     libmetis-dev libparmetis-dev libsuperlu-dist-dev \
     bc cmake git g++ make time sudo unzip vim wget gfortran ca-certificates && \
     rm -rf /var/lib/apt/lists/*
@@ -28,14 +28,6 @@ RUN wget https://download.pytorch.org/libtorch/cpu/libtorch-cxx11-abi-shared-wit
         --quiet -O libtorch.zip && \
     unzip -q libtorch.zip -d /opt && rm libtorch.zip
 
-# RapidJSON
-RUN cd /tmp && \
-    wget --quiet https://codeload.github.com/Tencent/rapidjson/tar.gz/24b5e7a -O rapidjson-24b5e7a.tar.gz && \
-    tar -xzf rapidjson-24b5e7a.tar.gz && cd rapidjson-24b5e7a && \
-    cmake -B build -DRAPIDJSON_BUILD_DOC=OFF -DRAPIDJSON_BUILD_EXAMPLES=OFF -DRAPIDJSON_BUILD_TESTS=OFF && \
-    cmake --build build --target install && \
-    cd /tmp && rm -r rapidjson-24b5e7a rapidjson-24b5e7a.tar.gz
-
 ENV CMAKE_PREFIX_PATH=/opt/libtorch/share/cmake
 
 # PEXSI
@@ -56,7 +48,7 @@ ADD https://api.github.com/repos/deepmodeling/abacus-develop/git/refs/heads/deve
 
 RUN git clone https://github.com/deepmodeling/abacus-develop.git --depth 1 && \
     cd abacus-develop && \
-    cmake -B build -DENABLE_MLALGO=ON -DENABLE_PEXSI=ON -DENABLE_LIBXC=ON -DENABLE_LIBRI=ON -DENABLE_RAPIDJSON=ON && \
+    cmake -B build -DENABLE_MLALGO=ON -DENABLE_PEXSI=ON -DENABLE_LIBXC=ON -DENABLE_LIBRI=ON -DENABLE_JSON=ON && \
     cmake --build build -j $(nproc) && \
     cmake --install build && \
     rm -rf build

Dockerfile.intel

@@ -2,7 +2,7 @@ FROM intel/oneapi-hpckit:2025.2.2-0-devel-ubuntu22.04
 
 RUN apt-get update && apt-get install -y \
     bc cmake git gnupg gcc g++ python3-numpy sudo wget vim unzip \
-    libcereal-dev libxc-dev libgtest-dev libgmock-dev libbenchmark-dev \
+    libcereal-dev libxc-dev libgtest-dev libgmock-dev libbenchmark-dev nlohmann-json3-dev \
     pkg-config build-essential autoconf automake libtool ca-certificates && \
     rm -rf /var/lib/apt/lists/*
 
@@ -22,14 +22,6 @@ RUN cd /tmp && \
     ln -s /usr/local/include/elpa_openmp-$ELPA_VER/elpa /usr/local/include/ && \
     cd /tmp && rm -rf elpa-$ELPA_VER
 
-# RapidJSON
-RUN cd /tmp && \
-    wget --quiet https://codeload.github.com/Tencent/rapidjson/tar.gz/24b5e7a -O rapidjson-24b5e7a.tar.gz && \
-    tar -xzf rapidjson-24b5e7a.tar.gz && cd rapidjson-24b5e7a && \
-    cmake -B build -DRAPIDJSON_BUILD_DOC=OFF -DRAPIDJSON_BUILD_EXAMPLES=OFF -DRAPIDJSON_BUILD_TESTS=OFF && \
-    cmake --build build --target install && \
-    cd /tmp && rm -r rapidjson-24b5e7a rapidjson-24b5e7a.tar.gz
-
 # LibTorch (Note: Using pre-built Torch library with MKL might cause issues)
 RUN wget -q https://download.pytorch.org/libtorch/cpu/libtorch-cxx11-abi-shared-with-deps-2.0.0%2Bcpu.zip -O /tmp/libtorch.zip && \
     unzip -q /tmp/libtorch.zip -d /opt && rm -f /tmp/libtorch.zip
@@ -43,7 +35,7 @@ RUN cd /tmp && git clone https://github.com/deepmodeling/abacus-develop.git --de
         -DENABLE_MLALGO=ON \
         -DENABLE_LIBXC=ON \
         -DENABLE_LIBRI=ON \
-        -DENABLE_RAPIDJSON=ON \
+        -DENABLE_JSON=ON \
         -DCMAKE_BUILD_TYPE=Release && \
     cmake --build build -j $(nproc) && \
     cmake --install build && \

cmake/CollectBuildInfoVars.cmake

@@ -361,12 +361,10 @@ else()
     set(ABACUS_GOOGLEBENCH_VERSION "Disabled")
 endif()
 
-if(DEFINED RapidJSON_DIR AND ENABLE_RAPIDJSON)
-    set(ABACUS_RAPIDJSON_VERSION "yes (path: ${RapidJSON_DIR})")
-elseif(ENABLE_RAPIDJSON)
-    set(ABACUS_RAPIDJSON_VERSION "yes (from git origin/master)")
+if(ENABLE_JSON)
+    set(ABACUS_JSON_VERSION "yes (nlohmann-json v${nlohmann_json_VERSION})")
 else()
-    set(ABACUS_RAPIDJSON_VERSION "no")
+    set(ABACUS_JSON_VERSION "no")
 endif()
 
 if(ENABLE_MLALGO)
@@ -458,7 +456,7 @@ if(ENABLE_EXX_DEV)
   message("                                      (EXX developing features enabled)")
 endif()
 message("                     DFT-D4         = ${ABACUS_DFTD4_VERSION}")
-message("                     RAPIDJSON      = ${ABACUS_RAPIDJSON_VERSION}")
+message("                     JSON           = ${ABACUS_JSON_VERSION}")
 message("                     PEXSI          = ${ABACUS_PEXSI_VERSION}")
 message("                     CNPY           = ${ABACUS_CNPY_VERSION}")
 message(" -------------------------------------------------------------------")

docs/advanced/install.md

@@ -99,6 +99,10 @@ vdw_d4_model d4    # or d4s for the smooth D4S model
 
 If `vdw_d4_xc` is set to `default`, ABACUS will infer the functional name from `dft_functional` or pseudopotential metadata and pass it to the DFT-D4 library. The `vdw_d4_model` keyword selects the dispersion model inside the DFT-D4 library; the default is `d4`, while `d4s` enables the smooth D4S model.
 
+## Build with JSON support
+
+ABACUS uses [nlohmann-json](https://github.com/nlohmann/json) for optional JSON output. To build ABACUS with JSON support, pass `-DENABLE_JSON=ON` to CMake.
+
 ## Build Unit Tests
 
 To build tests for ABACUS, define `BUILD_TESTING` flag. You can also specify path to local installation of [Googletest](https://github.com/google/googletest) by setting `GTEST_DIR` flags. If not found in local, the configuration process will try to download it automatically.