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Implement project_options for unified compiler settings #721

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103 changes: 8 additions & 95 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -266,12 +266,19 @@ endif()
# Library
# ============================

include(cmake/project_options.cmake)

# Project option interface target
add_library(project_options INTERFACE)
add_library(quest::project_options ALIAS project_options)

project_options_setup(project_options)

add_library(QuEST)

# Add namespaced alias to support inclusion of QuEST as a subproject
add_library(QuEST::QuEST ALIAS QuEST)

target_link_libraries(QuEST PRIVATE project_options)

# Set include directories
target_include_directories(QuEST
Expand All @@ -295,27 +302,6 @@ set_target_properties(QuEST PROPERTIES
# applies to the C interface when users specify USER_SOURCE,
# to attemptedly minimise user confusion. Users wishing to
# link QuEST with C++14 should separate compilation.
target_compile_features(QuEST
PUBLIC
c_std_11
cxx_std_17
)


# Turn on all compiler warnings
if (MSVC)
set(WARNING_FLAG /W4)
else()
set(WARNING_FLAG -Wall)
endif()

target_compile_options(QuEST
PRIVATE
$<$<COMPILE_LANGUAGE:CXX>:${WARNING_FLAG}>
$<$<COMPILE_LANGUAGE:C>:${WARNING_FLAG}>
)



# ============================
# Link optional dependencies
Expand Down Expand Up @@ -343,13 +329,6 @@ if (ENABLE_MULTITHREADING)
OpenMP::OpenMP_C
)

else()

# suppress GCC "unknown pragma" warning when OpenMP disabled
if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
target_compile_options(QuEST PRIVATE $<$<COMPILE_LANGUAGE:CXX>:-Wno-unknown-pragmas>)
endif()

endif()


Expand Down Expand Up @@ -468,72 +447,6 @@ set(DISABLE_DEPRECATION_WARNINGS ${DISABLE_DEPRECATION_WARNINGS})
set(COMPILE_HIP ${ENABLE_HIP})



# ============================
# Patch CPU performance
# ============================


# Patch performance of CPU std::complex arithmetic operator overloads.
# The cpu_subroutines.cpp file makes extensive use of std::complex operator
# overloads, and alas these are significantly slower than hand-rolled
# arithmetic, due to their NaN and inf checks, and interference with SIMD.
# It is crucial to pass additional optimisation flags to this file to restore
# hand-rolled performance (else QuEST v3 is faster than v4 eep). In theory,
# we can achieve this with specific, relatively 'safe' flags such as LLVM's:
# -ffinite-math-only -fno-signed-zeros -ffp-contract=fast
# However, it is a nuisance to find equivalent flags for different compilers
# and monitor their performance vs accuracy trade-offs. So instead, we use the
# much more aggressive and ubiquitous -Ofast flag to guarantee performance.
# This introduces many potentially dangerous optimisations, such as asserting
# associativity of flops, which would break techniques like Kahan summation.
# The cpu_subroutines.cpp must ergo be very conscious of these optimisations.
# We here also explicitly inform the file cpu_subroutines.cpp whether or not
# we are passing the flags, so it can detect/error when flags are forgotten.

if (CMAKE_BUILD_TYPE STREQUAL "Release")

# Release build will pass -Ofast when known for the given compiler, and
# fallback to giving a performance warning and proceeding with compilation

if (CMAKE_CXX_COMPILER_ID MATCHES "AppleClang|Clang|Cray|CrayClang|GNU|HP|Intel|IntelLLVM|NVHPC|NVIDIA|XL|XLClang")
set(patch_flags "-Ofast")
set(patch_macro "-DCOMPLEX_OVERLOADS_PATCHED=1")
elseif (CMAKE_CXX_COMPILER_ID MATCHES "HP")
set(patch_flags "+Ofast")
set(patch_macro "-DCOMPLEX_OVERLOADS_PATCHED=1")
elseif (CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
set(patch_flags "/fp:fast")
set(patch_macro "-DCOMPLEX_OVERLOADS_PATCHED=1")
else()
message(WARNING
"The compiler (${CMAKE_CXX_COMPILER_ID}) is unrecognised and so crucial optimisation flags have not been "
"passed to the CPU backend. These flags are necessary for full performance when performing complex algebra, "
"otherwise a slowdown of 3-50x may be observed. Please edit the root CMakeLists.txt to include flags which are "
"equivalent to GNU's -Ofast flag for your compiler (search this warning), or contact the QuEST developers for help."
)
set(patch_flags "")
set(patch_macro "-DCOMPLEX_OVERLOADS_PATCHED=0")
endif()

else()

# Non-release builds (e.g. Debug) will pass no optimisation flags, and will
# communicate to cpu_subroutines.cpp that this is intentional via a macro

set(patch_flags "")
set(patch_macro "-DCOMPLEX_OVERLOADS_PATCHED=0")

endif()

set_source_files_properties(
quest/src/cpu/cpu_subroutines.cpp
PROPERTIES
COMPILE_FLAGS "${patch_flags} ${patch_macro}"
)



# ============================
# Pass files to library
# ============================
Expand Down
61 changes: 61 additions & 0 deletions cmake/project_options.cmake
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Original file line number Diff line number Diff line change
@@ -0,0 +1,61 @@
function(project_options_setup target)
# C and C++ standards
target_compile_features(${target} INTERFACE cxx_std_20)
target_compile_features(${target} INTERFACE c_std_17)

# Identifying compilers and languages
set(clang_variants "AppleClang,ARMClang,Clang,CrayClang,FujitsuClang,IntelLLVM,XLClang,IBMClang")

# C and CXX compiler warnings
set(msvc_warnings
/W4
/permissive-
)
set(llvm_warnings
-Wall
-Wextra
-Wshadow
-Wpedantic
-Wno-unused-parameter
)
set(gcc_warnings
${llvm_warnings}
-Wlogical-op
$<$<BOOL:${ENABLE_MULTITHREADING}>:-Wno-unknown-pragmas>
)

foreach(language IN ITEMS C CXX)
target_compile_options(${target}
INTERFACE
$<$<COMPILE_LANG_AND_ID:${language},GNU>:$<BUILD_INTERFACE:${gcc_warnings}>>
$<$<COMPILE_LANG_AND_ID:${language},MSVC>:$<BUILD_INTERFACE:${msvc_warnings}>>
$<$<COMPILE_LANG_AND_ID:${language},${clang_variants}>:$<BUILD_INTERFACE:${llvm_warnings}>>
)
endforeach()

# CUDA and HIP Warnings
set(cuda_warnings
-Wall
-Wextra
-Wunused
-Wconversion
-Wshadow
)

target_compile_options(
${target}
INTERFACE
$<$<COMPILE_LANGUAGE:CUDA,HIP>:$<BUILD_INTERFACE:${cuda_warnings}>>
)

# Complex Arithmetic Option
foreach(language IN ITEMS C CXX)
target_compile_options(${target}
INTERFACE
$<$<COMPILE_LANG_AND_ID:${language},GNU>:$<BUILD_INTERFACE:-fcx-method=fortran>>
$<$<COMPILE_LANG_AND_ID:${language},MSVC>:$<BUILD_INTERFACE:/fp:precise>>
$<$<COMPILE_LANG_AND_ID:${language},${clang_variants}>:$<BUILD_INTERFACE:-fcomplex-arithmetic=improved>>
)
endforeach()

endfunction(project_options_setup)
25 changes: 0 additions & 25 deletions quest/src/cpu/cpu_subroutines.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -43,31 +43,6 @@
#include <algorithm>

using std::vector;


/*
* Beware that this file makes extensive use of std::complex (qcomp) operator
* overloads and so requires additional compiler flags to achieve hand-rolled
* arithmetic performance; otherwise a 3-50x slowdown may be observed. We here
* enforce that these flags were not forgotton (but may be deliberatedly avoided).
* Beware these flags may induce associativity and break e.g. Kakan summation.
*/

#if !defined(COMPLEX_OVERLOADS_PATCHED)
#error "Crucial, bespoke optimisation flags were not passed (or acknowledged) to cpu_subroutines.cpp which are necessary for full complex arithmetic performance."

#elif !COMPLEX_OVERLOADS_PATCHED

#if defined(_MSC_VER)
#pragma message("Warning: The CPU backend is being deliberately compiled without the necessary flags to obtain full complex arithmetic performance.")
#else
#warning "The CPU backend is being deliberately compiled without the necessary flags to obtain full complex arithmetic performance."
#endif

#endif



/*
* GETTERS
*/
Expand Down