add to vw_core

Author: bassmang

CMakeLists.txt

@@ -178,6 +178,7 @@ option(VW_BUILD_VW_C_WRAPPER "Enable building the c_wrapper project" ON)
 option(vw_BUILD_NET_CORE "Build .NET Core targets" OFF)
 option(vw_BUILD_NET_FRAMEWORK "Build .NET Framework targets" OFF)
 option(VW_BUILD_WASM "Add WASM target" OFF)
+option(STD_INV_SQRT "Use standard library inverse square root" OFF)
 
 if(VW_INSTALL AND NOT VW_ZLIB_SYS_DEP)
   message(WARNING "Installing with a vendored version of zlib is not recommended. Use VW_ZLIB_SYS_DEP to use a system dependency or specify VW_INSTALL=OFF to silence this warning.")

vowpalwabbit/core/CMakeLists.txt

@@ -440,6 +440,10 @@ if (MSVC_IDE)
   target_sources(vw_core PRIVATE $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/vw_types.natvis> )
 endif()
 
+if(STD_INV_SQRT)
+  target_compile_definitions(vw_core PUBLIC STD_INV_SQRT)
+endif()
+
 # Clang-cl on Windows has issues with our usage of SIMD types. Turn it off explicitly for Windows + clang-cl to mitigate.
 # See issue #
 if(WIN32 AND CMAKE_CXX_COMPILER_ID MATCHES "Clang")

vowpalwabbit/core/src/reductions/gd.cc

@@ -153,6 +153,7 @@ VW_WARNING_STATE_POP
 
 static inline float inv_sqrt(float x)
 {
+  return 1.f / std::sqrt(x);
 #if defined(STD_INV_SQRT)
   return 1.f / std::sqrt(x);
 #endif