我今天克隆了Eigen（hg clone https://bitbucket.org/eigen/eigen/）以获得Eigen 3.3。我无法使用AVX扩展。添加标志 -march = native 或 -mavx 时，我在VERBOSE=1 make check上得到以下输出（我自己的想法如下）
[ 0%] Building CXX object unsupported/test/CMakeFiles/cxx11_tensor_io.dir/cxx11_tensor_io.cpp.o
cd /home/username/code/eigen/build/unsupported/test && /usr/bin/c++ -mavx -pedantic -Wall -Wextra -Wundef -Wcast-align -Wchar-subscripts -Wnon-virtual-dtor -Wunused-local-typedefs -Wpointer-arith -Wwrite-strings -Wformat-security -Wlogical-op -Wdouble-promotion -Wno-psabi -Wno-variadic-macros -Wno-long-long -fno-check-new -fno-common -fstrict-aliasing -ansi -O3 -DNDEBUG -I/home/username/code/eigen/build/unsupported/test -I/home/username/code/eigen/unsupported/test -I/home/username/code/eigen -I/home/username/code/eigen/build -I/home/username/code/eigen/unsupported/test/../../test -I/home/username/code/eigen/unsupported/test/../../unsupported -I/home/username/code/eigen/unsupported/test/../../Eigen -I/home/username/code/eigen/build/unsupported/test/../../test -DEIGEN_TEST_MAX_SIZE=320 -DEIGEN_TEST_FUNC=cxx11_tensor_io -o CMakeFiles/cxx11_tensor_io.dir/cxx11_tensor_io.cpp.o -c /home/username/code/eigen/unsupported/test/cxx11_tensor_io.cpp
In file included from /home/username/code/eigen/Eigen/Core:369:0,
from /home/username/code/eigen/Eigen/QR:11,
from /home/username/code/eigen/unsupported/test/../../test/main.h:256,
from /home/username/code/eigen/unsupported/test/cxx11_tensor_io.cpp:10:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h: In function ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(8) float; typename Eigen::internal::unpacket_traits<T>::type = float]’:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h:398:81: error: cannot convert ‘Eigen::internal::unpacket_traits<__vector(4) float>::type {aka __vector(4) float}’ to ‘float’ in return
return predux(_mm_add_ps(_mm256_castps256_ps128(a),_mm256_extractf128_ps(a,1)));
^
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h: In function ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(4) double; typename Eigen::internal::unpacket_traits<T>::type = double]’:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h:402:81: error: cannot convert ‘Eigen::internal::unpacket_traits<__vector(2) double>::type {aka __vector(2) double}’ to ‘double’ in return
return predux(_mm_add_pd(_mm256_castpd256_pd128(a),_mm256_extractf128_pd(a,1)));
^
In file included from /home/username/code/eigen/Eigen/Core:356:0,
from /home/username/code/eigen/Eigen/QR:11,
from /home/username/code/eigen/unsupported/test/../../test/main.h:256,
from /home/username/code/eigen/unsupported/test/cxx11_tensor_io.cpp:10:
/home/username/code/eigen/Eigen/src/Core/GenericPacketMath.h: In instantiation of ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(4) float; typename Eigen::internal::unpacket_traits<T>::type = __vector(4) float]’:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h:398:81: required from here
/home/username/code/eigen/Eigen/src/Core/GenericPacketMath.h:324:13: error: ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(4) float; typename Eigen::internal::unpacket_traits<T>::type = __vector(4) float]’ conflicts with a previous declaration
{ return a; }
^
In file included from /home/username/code/eigen/Eigen/Core:369:0,
from /home/username/code/eigen/Eigen/QR:11,
from /home/username/code/eigen/unsupported/test/../../test/main.h:256,
from /home/username/code/eigen/unsupported/test/cxx11_tensor_io.cpp:10:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h:396:38: note: previous declaration ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(8) float; typename Eigen::internal::unpacket_traits<T>::type = float]’
template<> EIGEN_STRONG_INLINE float predux<Packet8f>(const Packet8f& a)
^
In file included from /home/username/code/eigen/Eigen/Core:356:0,
from /home/username/code/eigen/Eigen/QR:11,
from /home/username/code/eigen/unsupported/test/../../test/main.h:256,
from /home/username/code/eigen/unsupported/test/cxx11_tensor_io.cpp:10:
/home/username/code/eigen/Eigen/src/Core/GenericPacketMath.h:323:91: note: -fabi-version=6 (or =0) avoids this error with a change in mangling
template<typename Packet> EIGEN_DEVICE_FUNC inline typename unpacket_traits<Packet>::type predux(const Packet& a)
^
/home/username/code/eigen/Eigen/src/Core/GenericPacketMath.h: In instantiation of ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(2) double; typename Eigen::internal::unpacket_traits<T>::type = __vector(2) double]’:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h:402:81: required from here
/home/username/code/eigen/Eigen/src/Core/GenericPacketMath.h:324:13: error: ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(2) double; typename Eigen::internal::unpacket_traits<T>::type = __vector(2) double]’ conflicts with a previous declaration
{ return a; }
^
In file included from /home/username/code/eigen/Eigen/Core:369:0,
from /home/username/code/eigen/Eigen/QR:11,
from /home/username/code/eigen/unsupported/test/../../test/main.h:256,
from /home/username/code/eigen/unsupported/test/cxx11_tensor_io.cpp:10:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h:400:39: note: previous declaration ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(4) double; typename Eigen::internal::unpacket_traits<T>::type = double]’
template<> EIGEN_STRONG_INLINE double predux<Packet4d>(const Packet4d& a)
^
In file included from /home/username/code/eigen/Eigen/Core:356:0,
from /home/username/code/eigen/Eigen/QR:11,
from /home/username/code/eigen/unsupported/test/../../test/main.h:256,
from /home/username/code/eigen/unsupported/test/cxx11_tensor_io.cpp:10:
/home/username/code/eigen/Eigen/src/Core/GenericPacketMath.h:323:91: note: -fabi-version=6 (or =0) avoids this error with a change in mangling
template<typename Packet> EIGEN_DEVICE_FUNC inline typename unpacket_traits<Packet>::type predux(const Packet& a)
^
In file included from /home/username/code/eigen/Eigen/Core:369:0,
from /home/username/code/eigen/Eigen/QR:11,
from /home/username/code/eigen/unsupported/test/../../test/main.h:256,
from /home/username/code/eigen/unsupported/test/cxx11_tensor_io.cpp:10:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h: In function ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(8) float; typename Eigen::internal::unpacket_traits<T>::type = float]’:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h:399:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h: In function ‘typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(const Packet&) [with Packet = __vector(4) double; typename Eigen::internal::unpacket_traits<T>::type = double]’:
/home/username/code/eigen/Eigen/src/Core/arch/AVX/PacketMath.h:403:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
make[3]: *** [unsupported/test/CMakeFiles/cxx11_tensor_io.dir/cxx11_tensor_io.cpp.o] Fehler 1
make[3]: Verzeichnis »/home/username/code/eigen/build« wird verlassen
make[2]: *** [unsupported/test/CMakeFiles/cxx11_tensor_io.dir/all] Fehler 2
make[2]: Verzeichnis »/home/username/code/eigen/build« wird verlassen
make[1]: *** [CMakeFiles/check.dir/rule] Fehler 2
make[1]: Verzeichnis »/home/username/code/eigen/build« wird verlassen
make: *** [check] Fehler 2
由于typename Eigen::internal::unpacket_traits<T>::type Eigen::internal::predux(cost Packet&)的定义存在冲突，有时包含__vector(4) float，有时包含__vector(2) float，因此可能与AVX和SSE扩展的代码存在冲突？但是，它也只发生在 -mavx 中，所以我暂时没有想法。
我没有成功用谷歌搜索（太新了？），我希望有人可以提供帮助。