Moving over C++ API of CAGRA+hnswlib from RAFT (#229)

Authors:
  - Divye Gala (https://github.com/divyegala)

Approvers:
  - Ben Frederickson (https://github.com/benfred)

URL: #229

cpp/CMakeLists.txt

@@ -56,6 +56,7 @@ option(BUILD_TESTS "Build cuvs unit-tests" ON)
 option(BUILD_C_LIBRARY "Build raft C API library" OFF)
 option(BUILD_C_TESTS "Build raft C API tests" OFF)
 option(BUILD_ANN_BENCH "Build cuVS ann benchmarks" OFF)
+option(BUILD_CAGRA_HNSWLIB "Build CAGRA+hnswlib interface" ON)
 option(CUDA_ENABLE_KERNELINFO "Enable kernel resource usage info" OFF)
 option(CUDA_ENABLE_LINEINFO
        "Enable the -lineinfo option for nvcc (useful for cuda-memcheck / profiler)" OFF
@@ -192,6 +193,10 @@ if(BUILD_ANN_BENCH)
   rapids_cpm_gbench(BUILD_STATIC)
 endif()
 
+if(BUILD_CAGRA_HNSWLIB)
+  include(cmake/thirdparty/get_hnswlib.cmake)
+endif()
+
 # ##################################################################################################
 # * cuvs ---------------------------------------------------------------------
 
@@ -399,6 +404,7 @@ add_library(
   src/neighbors/detail/cagra/search_single_cta_half_uint64_dim256_t16.cu
   src/neighbors/detail/cagra/search_single_cta_half_uint64_dim512_t32.cu
   src/neighbors/detail/cagra/search_single_cta_half_uint64_dim1024_t32.cu
+  $<$<BOOL:${BUILD_CAGRA_HNSWLIB}>:src/neighbors/hnsw.cpp>
   src/neighbors/ivf_flat_index.cpp
   src/neighbors/ivf_flat/ivf_flat_build_extend_float_int64_t.cu
   src/neighbors/ivf_flat/ivf_flat_build_extend_int8_t_int64_t.cu
@@ -492,6 +498,11 @@ if(NOT BUILD_CPU_ONLY)
   )
 endif()
 
+if(BUILD_CAGRA_HNSWLIB)
+  target_link_libraries(cuvs PRIVATE hnswlib::hnswlib)
+  target_compile_definitions(cuvs PUBLIC CUVS_BUILD_CAGRA_HNSWLIB)
+endif()
+
 # Endian detection
 include(TestBigEndian)
 test_big_endian(BIG_ENDIAN)