make misc/test_blas failed in ubuntu14.04

[shutcode]

Summary

after running configure, failed to make misc/test_blas
I'm sure openblas is installed(apt-get and install from source),and the link flags are correctly set. error info as follows

test_blas.cpp:(.text+0x187)：undefined reference to `sgemm_'
test_blas.cpp:(.text+0x346)：undefined reference to `sgeqrf_'
collect2: error: ld returned 1 exit status

I have tried solutions from #15 and #131

Platform

OS: ubuntu 14.04
Faiss version: 1fe2872

Faiss compilation options:

g++ -std=c++11  -fopenmp  -lopenblas -llapack  -o misc/test_blas misc/test_blas.cpp
#or 
g++ -std=c++11  -fopenmp  -lopenblas -llapack -L/opt/OpenBLAS/lib -I/opt/OpenBLAS/include -o misc/test_blas misc/test_blas.cpp

Running on :

• CPU

Reproduction instructions

./configure
make misc/test_blas.cpp

test_blas.cpp:(.text+0x187)：undefined reference to `sgemm_'
test_blas.cpp:(.text+0x346)：undefined reference to `sgeqrf_'
collect2: error: ld returned 1 exit status
ldconfig -p |grep openblas
	libopenblas.so.0 (libc6,x86-64) => /usr/local/lib/libopenblas.so.0
	libopenblas.so.0 (libc6,x86-64) => /usr/lib/libopenblas.so.0
	libopenblas.so (libc6,x86-64) => /usr/local/lib/libopenblas.so
	libopenblas.so (libc6,x86-64) => /usr/lib/libopenblas.so
 ldconfig -p |grep lapack
	liblapack.so.3 (libc6,x86-64) => /usr/lib/liblapack.so.3
	liblapack.so (libc6,x86-64) => /usr/lib/liblapack.so

[beauby]

1. What does g++ --version say?
2. What happens if you put -lopenblas -llapack at the end of the line?

i.e. g++ -std=c++11 -fopenmp -o misc/test_blas misc/test_blas.cpp -lopenblas -llapack.

[shutcode]

1. g++ version

Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.4-2ubuntu1~14.04.3' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libmudflap --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.3)

2. It is OK, why?

~/faiss/misc$ g++ -std=c++11 -fopenmp -o misc/test_blas misc/test_blas.cpp -lopenblas -llapack
~/faiss/misc$ ./test_blas 
BLAS test
errors=
 0.000  0.000  0.000  0.000  0.000  0.000  0.000 -0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000 
 0.000 -0.000  0.000  0.000  0.000  0.000  0.000 -0.000  0.000  0.000  0.000  0.000 -0.000  0.000  0.000 -0.000 -0.000  0.000  0.000  0.000 
 0.000  0.000  0.000  0.000  0.000 -0.000  0.000 -0.000 -0.000  0.000  0.000  0.000  0.000 -0.000  0.000  0.000  0.000  0.000  0.000  0.000 
 0.000  0.000  0.000  0.000  0.000 -0.000  0.000 -0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000 
 0.000  0.000  0.000  0.000 -0.000  0.000 -0.000  0.000 -0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000 -0.000 
 0.000  0.000  0.000  0.000  0.000 -0.000  0.000  0.000  0.000 -0.000 -0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000 -0.000  0.000 
 0.000  0.000 -0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000 -0.000  0.000  0.000  0.000 -0.000  0.000  0.000  0.000  0.000 -0.000 
 0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000 -0.000 -0.000  0.000  0.000  0.000  0.000 
 0.000  0.000  0.000 -0.000  0.000 -0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000 -0.000 -0.000  0.000  0.000  0.000  0.000  0.000 
 0.000  0.000  0.000 -0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000 -0.000  0.000  0.000  0.000  0.000  0.000 
Intentional Lapack error (appears only for 64-bit INTEGER):
info=0000064b00000000
Lapack uses 32-bit integers

[beauby]

This is because the linker is sensitive to the order in which libraries are linked. I'll update the Makefile.
Thanks for reporting this!