remove WITH_FAST_MATH option (#19149)

test=develop

CMakeLists.txt

@@ -71,7 +71,6 @@ option(WITH_GRPC     "Use grpc as the default rpc framework"            ${WITH_D
 option(WITH_INFERENCE_API_TEST   "Test fluid inference C++ high-level api interface"  OFF)
 option(WITH_HIGH_LEVEL_API_TEST   "Test fluid python high-level api interface"  OFF)
 option(PY_VERSION       "Compile PaddlePaddle with python3 support"     ${PY_VERSION})
-option(WITH_FAST_MATH   "Make use of fast math library, might affect the precision to some extent" ON)
 option(WITH_DGC   "Use DGC(Deep Gradient Compression) or not" ON)
 option(SANITIZER_TYPE "Choose the type of sanitizer, options are: Address, Leak, Memory, Thread, Undefined" OFF)
 

cmake/cuda.cmake

@@ -186,10 +186,6 @@ list(APPEND CUDA_NVCC_FLAGS "-std=c++11")
 list(APPEND CUDA_NVCC_FLAGS "-Xcompiler -fPIC")
 endif(NOT WIN32)
 
-if(WITH_FAST_MATH)
-  # Make use of fast math library. https://docs.nvidia.com/cuda/cuda-compiler-driver-nvcc/index.html
-  list(APPEND CUDA_NVCC_FLAGS "--use_fast_math")
-endif()
 # in cuda9, suppress cuda warning on eigen 
 list(APPEND CUDA_NVCC_FLAGS "-w")
 # Set :expt-relaxed-constexpr to suppress Eigen warnings

cmake/external/eigen.cmake

@@ -3,15 +3,6 @@ INCLUDE(ExternalProject)
 SET(EIGEN_SOURCE_DIR ${THIRD_PARTY_PATH}/eigen3)
 SET(EIGEN_INCLUDE_DIR ${EIGEN_SOURCE_DIR}/src/extern_eigen3)
 INCLUDE_DIRECTORIES(${EIGEN_INCLUDE_DIR})
-if(NOT WITH_FAST_MATH)
-  # EIGEN_FAST_MATH: https://eigen.tuxfamily.org/dox/TopicPreprocessorDirectives.html
-  # enables some optimizations which might affect the accuracy of the result. 
-  # This currently enables the SSE vectorization of sin() and cos(), 
-  # and speedups sqrt() for single precision.
-  # Defined to 1 by default. Define it to 0 to disable.
-  add_definitions(-DEIGEN_FAST_MATH=0)
-endif()
-
 
 if(WIN32)
     set(EIGEN_GIT_REPOSITORY https://github.com/wopeizl/eigen-git-mirror)