Does Python SciPy need BLAS?


    Blas ( libraries not found.
    Directories to search for the libraries can be specified in the
    numpy/distutils/site.cfg file (section [blas]) or by setting
    the BLAS environment variable.

Which tar do I need to download off this site?

I’ve tried the fortrans, but I keep getting this error (after setting the environment variable obviously).

Asked By: joedborg



I guess you are talking about installation in Ubuntu. Just use:

apt-get install python-numpy python-scipy

That should take care of the BLAS libraries compiling as well. Else, compiling the BLAS libraries is very difficult.

Answered By: Vishwanath

The SciPy webpage used to provide build and installation instructions, but the instructions there now rely on OS binary distributions. To build SciPy (and NumPy) on operating systems without precompiled packages of the required libraries, you must build and then statically link to the Fortran libraries BLAS and LAPACK:

mkdir -p ~/src/
cd ~/src/
tar xzf blas.tgz
cd BLAS-*

## NOTE: The selected Fortran compiler must be consistent for BLAS, LAPACK, NumPy, and SciPy.
## For GNU compiler on 32-bit systems:
#g77 -O2 -fno-second-underscore -c *.f                     # with g77
#gfortran -O2 -std=legacy -fno-second-underscore -c *.f    # with gfortran
## OR for GNU compiler on 64-bit systems:
#g77 -O3 -m64 -fno-second-underscore -fPIC -c *.f                     # with g77
gfortran -O3 -std=legacy -m64 -fno-second-underscore -fPIC -c *.f    # with gfortran
## OR for Intel compiler:
#ifort -FI -w90 -w95 -cm -O3 -unroll -c *.f

# Continue below irrespective of compiler:
ar r libfblas.a *.o
ranlib libfblas.a
rm -rf *.o
export BLAS=~/src/BLAS-*/libfblas.a

Execute only one of the five g77/gfortran/ifort commands. I have commented out all, but the gfortran which I use. The subsequent LAPACK installation requires a Fortran 90 compiler, and since both installs should use the same Fortran compiler, g77 should not be used for BLAS.

Next, you’ll need to install the LAPACK stuff. The SciPy webpage’s instructions helped me here as well, but I had to modify them to suit my environment:

mkdir -p ~/src
cd ~/src/
tar xzf lapack.tgz
cd lapack-*/
cp INSTALL/          # On Linux with lapack-3.2.1 or newer
make lapacklib
make clean
export LAPACK=~/src/lapack-*/liblapack.a

Update on 3-Sep-2015:
Verified some comments today (thanks to all): Before running make lapacklib edit the file and add -fPIC option to OPTS and NOOPT settings. If you are on a 64bit architecture or want to compile for one, also add -m64. It is important that BLAS and LAPACK are compiled with these options set to the same values. If you forget the -fPIC SciPy will actually give you an error about missing symbols and will recommend this switch. The specific section of looks like this in my setup:

FORTRAN  = gfortran 
OPTS     = -O2 -frecursive -fPIC -m64
NOOPT    = -O0 -frecursive -fPIC -m64
LOADER   = gfortran

On old machines (e.g. RedHat 5), gfortran might be installed in an older version (e.g. 4.1.2) and does not understand option -frecursive. Simply remove it from the file in such cases.

The lapack test target of the Makefile fails in my setup because it cannot find the blas libraries. If you are thorough you can temporarily move the blas library to the specified location to test the lapack. I’m a lazy person, so I trust the devs to have it working and verify only in SciPy.

Answered By: cfi

Following the instructions given by ‘cfi’ works for me, although there are a few pieces they left out that you might need:

1) Your lapack directory, after unzipping, may be called lapack-X-Y (some version number), so you can just rename that to LAPACK.

cd ~/src
mv lapack-[tab] LAPACK

2) In that directory, you may need to do:

cd ~/src/LAPACK 
cp lapack_LINUX.a libflapack.a
Answered By: RickG

If you need to use the latest versions of SciPy rather than the packaged version, without going through the hassle of building BLAS and LAPACK, you can follow the below procedure.

Install linear algebra libraries from repository (for Ubuntu),

sudo apt-get install gfortran libopenblas-dev liblapack-dev

Then install SciPy, (after downloading the SciPy source): python install or

pip install scipy

As the case may be.

Answered By: AIB

On Fedora, this works:

 yum install lapack lapack-devel blas blas-devel
 pip install numpy
 pip install scipy

Remember to install ‘lapack-devel‘ and ‘blas-devel‘ in addition to ‘blas’ and ‘lapack’ otherwise you’ll get the error you mentioned or the “numpy.distutils.system_info.LapackNotFoundError” error.

Answered By: Muneeb Ali

For Windows users there is a nice binary package by Chris (warning: it’s a pretty large download, 191 MB):

Answered By: jmunsch

Try using

sudo apt-get install python3-scipy
Answered By: 李华强
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