Add cmake (#83)

.gitignore

@@ -10,3 +10,7 @@ out/
 buildSrc/es-knn-offline-repo-*
 oss/*
 *.iml
+jni/CMakeCache.txt
+jni/CMakeFiles
+jni/Makefile
+jni/cmake_install.cmake

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "jni/external/nmslib"]
+	path = jni/external/nmslib
+	url = https://github.com/nmslib/nmslib.git

README.md

@@ -20,6 +20,18 @@ The package uses the [Gradle](https://docs.gradle.org/5.5.1/userguide/userguide.
 2. To build from command line set `JAVA_HOME` to point to a JDK >=12
 3. Run `./gradlew build`
 
+## Building JNI Library
+
+To build the JNI Library used to incorporate NMSLIB functionality, follow these steps:
+
+```
+cd jni
+cmake .
+make
+``` 
+
+The library will be placed in the `buildSrc` directory.
+
 ### Debugging
 
 Sometimes it is useful to attach a debugger to either the Elasticsearch cluster or the integration test runner to see what's going on. For running unit tests, hit **Debug** from the IDE's gutter to debug the tests. For the Elasticsearch cluster, first, make sure that the debugger is listening on port `5005`. Then, to debug the cluster code, run:

jni/CMakeLists.txt

@@ -0,0 +1,56 @@
+#
+#   Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+#   Licensed under the Apache License, Version 2.0 (the "License").
+#   You may not use this file except in compliance with the License.
+#   A copy of the License is located at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   or in the "license" file accompanying this file. This file is distributed
+#   on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+#   express or implied. See the License for the specific language governing
+#   permissions and limitations under the License.
+#
+
+cmake_minimum_required(VERSION 2.8)
+
+project(KNNIndexV1_7_3_6)
+
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD_REQUIRED True)
+
+# Target Library to be built
+set(KNN_INDEX KNNIndexV1_7_3_6)
+
+# Check if similarity search exists
+find_path(NMS_REPO_DIR NAMES similarity_search PATHS ${CMAKE_CURRENT_SOURCE_DIR}/external/nmslib REQUIRED)
+
+# If not, pull the updated submodule
+if (NOT EXISTS ${NMS_REPO_DIR})
+    message(STATUS "Could not find nmslib. Pulling updated submodule.")
+    execute_process(COMMAND git submodule update --init -- external/nmslib WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+endif ()
+
+# Add the subdirectory so it is possible to use its targets
+add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/external/nmslib/similarity_search)
+
+# Set OS specific variables
+if (${CMAKE_SYSTEM_NAME} STREQUAL Darwin)
+    set(JVM_OS_TYPE darwin)
+    set(LIB_EXT .jnilib)
+elseif(${CMAKE_SYSTEM_NAME} STREQUAL Linux)
+    set(JVM_OS_TYPE linux)
+    set(LIB_EXT .so)
+else()
+    message( FATAL_ERROR "Unable to run on system: ${CMAKE_SYSTEM_NAME}")
+endif()
+
+# Compile the library
+add_library(${KNN_INDEX} SHARED ${CMAKE_CURRENT_SOURCE_DIR}/src/v1736/com_amazon_opendistroforelasticsearch_knn_index_v1736_KNNIndex.cpp)
+target_link_libraries(${KNN_INDEX} NonMetricSpaceLib)
+target_include_directories(${KNN_INDEX} PRIVATE $ENV{JAVA_HOME}/include $ENV{JAVA_HOME}/include/${JVM_OS_TYPE} ${CMAKE_CURRENT_SOURCE_DIR}/external/nmslib/similarity_search/include)
+
+set_target_properties(${KNN_INDEX} PROPERTIES SUFFIX ${LIB_EXT})
+set_target_properties(${KNN_INDEX} PROPERTIES POSITION_INDEPENDENT_CODE ON)
+set_target_properties(${KNN_INDEX} PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/../buildSrc)