Remove lz4 compression with external memory.

.github/workflows/main.yml

@@ -21,12 +21,12 @@ jobs:
         submodules: 'true'
     - name: Install system packages
       run: |
-        brew install lz4 ninja libomp
+        brew install ninja libomp
     - name: Build gtest binary
       run: |
         mkdir build
         cd build
-        cmake .. -DGOOGLE_TEST=ON -DUSE_OPENMP=ON -DUSE_DMLC_GTEST=ON -DPLUGIN_LZ4=ON -DPLUGIN_DENSE_PARSER=ON -GNinja
+        cmake .. -DGOOGLE_TEST=ON -DUSE_OPENMP=ON -DUSE_DMLC_GTEST=ON -DPLUGIN_DENSE_PARSER=ON -GNinja
         ninja -v
     - name: Run gtest binary
       run: |

CMakeLists.txt

@@ -62,7 +62,6 @@ set(ENABLED_SANITIZERS "address" "leak" CACHE STRING
   "Semicolon separated list of sanitizer names. E.g 'address;leak'. Supported sanitizers are
 address, leak, undefined and thread.")
 ## Plugins
-option(PLUGIN_LZ4 "Build lz4 plugin" OFF)
 option(PLUGIN_DENSE_PARSER "Build dense parser plugin" OFF)
 option(PLUGIN_RMM "Build with RAPIDS Memory Manager (RMM)" OFF)
 ## TODO: 1. Add check if DPC++ compiler is used for building
@@ -92,6 +91,9 @@ endif (R_LIB AND GOOGLE_TEST)
 if (USE_AVX)
   message(SEND_ERROR  "The option 'USE_AVX' is deprecated as experimental AVX features have been removed from XGBoost.")
 endif (USE_AVX)
+if (PLUGIN_LZ4)
+  message(SEND_ERROR  "The option 'PLUGIN_LZ4' is removed from XGBoost.")
+endif (PLUGIN_LZ4)
 if (PLUGIN_RMM AND NOT (USE_CUDA))
   message(SEND_ERROR "`PLUGIN_RMM` must be enabled with `USE_CUDA` flag.")
 endif (PLUGIN_RMM AND NOT (USE_CUDA))

Jenkinsfile

@@ -147,7 +147,7 @@ def BuildCPU() {
       # This step is not necessary, but here we include it, to ensure that DMLC_CORE_USE_CMAKE flag is correctly propagated
       # We want to make sure that we use the configured header build/dmlc/build_config.h instead of include/dmlc/build_config_default.h.
       # See discussion at https://github.com/dmlc/xgboost/issues/5510
-    ${dockerRun} ${container_type} ${docker_binary} tests/ci_build/build_via_cmake.sh -DPLUGIN_LZ4=ON -DPLUGIN_DENSE_PARSER=ON
+    ${dockerRun} ${container_type} ${docker_binary} tests/ci_build/build_via_cmake.sh -DPLUGIN_DENSE_PARSER=ON
     ${dockerRun} ${container_type} ${docker_binary} bash -c "cd build && ctest --extra-verbose"
     """
     // Sanitizer test

plugin/CMakeLists.txt

@@ -1,13 +1,3 @@
-if (PLUGIN_LZ4)
-  target_sources(objxgboost PRIVATE ${xgboost_SOURCE_DIR}/plugin/lz4/sparse_page_lz4_format.cc)
-  find_path(LIBLZ4_INCLUDE_DIR lz4.h)
-  find_library(LIBLZ4_LIBRARY NAMES lz4)
-  message(STATUS "LIBLZ4_INCLUDE_DIR = ${LIBLZ4_INCLUDE_DIR}")
-  message(STATUS "LIBLZ4_LIBRARY = ${LIBLZ4_LIBRARY}")
-  target_include_directories(objxgboost PUBLIC ${LIBLZ4_INCLUDE_DIR})
-  target_link_libraries(objxgboost PUBLIC ${LIBLZ4_LIBRARY})
-endif (PLUGIN_LZ4)
-
 if (PLUGIN_DENSE_PARSER)
   target_sources(objxgboost PRIVATE ${xgboost_SOURCE_DIR}/plugin/dense_parser/dense_libsvm.cc)
 endif (PLUGIN_DENSE_PARSER)