Installation issue on mac

[SteveDiamond]

Please read this first

If you are have a problem that SCS struggles with you can pass a string to the write_data_filename argument and SCS will dump a file containing the problem to disk. Zip the file and send it to us or attach it to this bug report for easy reproduction of the issue.

A common cause of issues is not linking BLAS/LAPACK libraries correctly. If you are having this issue please search for resources on installing and linking these libraries first. You can try openblas if you need a BLAS library.

Specifications

• OS: Mac, latest OS
• SCS Version: 2.1.4
• Compiler:

Description

Someone with a vanilla Python 3 setup tried to install SCS and got an import error.

How to reproduce

The problem occurred on two different machines with vanilla (no conda or venv) Python 3 setups.

Additional information

Output

>>> import cvxpy
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cvxpy/__init__.py", line 27, in <module>
    from cvxpy.problems.problem import Problem
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cvxpy/problems/problem.py", line 35, in <module>
    from cvxpy.reductions import InverseData
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cvxpy/reductions/__init__.py", line 32, in <module>
    from cvxpy.reductions.solvers.solving_chain import SolvingChain
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cvxpy/reductions/solvers/solving_chain.py", line 21, in <module>
    from cvxpy.reductions.solvers import defines as slv_def
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cvxpy/reductions/solvers/defines.py", line 98, in <module>
    INSTALLED_SOLVERS = installed_solvers()
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cvxpy/reductions/solvers/defines.py", line 87, in installed_solvers
    if solver.is_installed():
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cvxpy/reductions/solvers/solver.py", line 59, in is_installed
    self.import_solver()
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/cvxpy/reductions/solvers/conic_solvers/scs_conif.py", line 134, in import_solver
    import scs
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/scs/__init__.py", line 5, in <module>
    import _scs_direct
ImportError: dlopen(/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/_scs_direct.cpython-38-darwin.so, 2): Library not loaded: @rpath/libmkl_rt.1.dylib
  Referenced from: /Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/_scs_direct.cpython-38-darwin.so
  Reason: image not found

[bodono]

SCS relies on Numpy to tell it where these libraries are on your system, using the get_info commands:

from numpy.distutils.system_info import get_info
print(get_info("blas_opt"))  # best blas install
print(get_info("lapack_opt"))  # best lapack install
print(get_info("blas"))  # fall back blas install
print(get_info("lapack"))  # fall back lapack install

What do the outputs of running those commands yield?

After that: Does libmkl_rt exist on the machine?

If not the user needs to install a blas / lapack lib and reinstall SCS.

If it does exist, then it sounds like something is wrong with the DYLD_LIBRARY_PATH environment variable (try also LD_RUNPATH_SEARCH_PATH, LD_LIBRARY_PATH etc., I'm not exactly sure which one is best). If you append the location of the mkl library to the env variable it should pick it up.

[enricogrande]

I had a similar problem with scs>=3.0.0, Mac OS X 10.14.6 and python 3.7.7.

The error message I receive is the following

In [2]: import scs
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-2-97fdeadba5ba> in <module>
----> 1 import scs

~/virtualenvs/dev/lib/python3.7/site-packages/scs/__init__.py in <module>
      2 from warnings import warn
      3 from scipy import sparse
----> 4 import _scs_direct
      5 
      6 __version__ = _scs_direct.version()

ImportError: dlopen(/Users/enrico/virtualenvs/dev/lib/python3.7/site-packages/_scs_direct.cpython-37m-darwin.so, 2): Symbol not found: _aligned_alloc
  Referenced from: /Users/enrico/virtualenvs/dev/lib/python3.7/site-packages/scs/.dylibs/libgomp.1.dylib (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib
 in /Users/enrico/virtualenvs/dev/lib/python3.7/site-packages/scs/.dylibs/libgomp.1.dylib

Running the commands suggested by @bodono produces

Python 3.7.7 (v3.7.7:d7c567b08f, Mar 10 2020, 02:56:16) 
Type 'copyright', 'credits' or 'license' for more information
IPython 7.31.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from numpy.distutils.system_info import get_info
   ...: print(get_info("blas_opt"))  # best blas install
   ...: print(get_info("lapack_opt"))  # best lapack install
   ...: print(get_info("blas"))  # fall back blas install
   ...: print(get_info("lapack"))  # fall back lapack install
{'extra_compile_args': ['-msse3', '-I/System/Library/Frameworks/vecLib.framework/Headers'], 'extra_link_args': ['-Wl,-framework', '-Wl,Accelerate'], 'define_macros': [('NO_ATLAS_INFO', 3), ('HAVE_CBLAS', None)]}
{'extra_compile_args': ['-msse3', '-I/System/Library/Frameworks/vecLib.framework/Headers'], 'extra_link_args': ['-Wl,-framework', '-Wl,Accelerate'], 'define_macros': [('NO_ATLAS_INFO', 3), ('HAVE_CBLAS', None)]}
/var/folders/9r/gd86060902l6q82mdjnv8sgr0000gn/T/tmp4h4phrhy/source.c:1:10: fatal error: 'cblas.h' file not found
#include <cblas.h>
         ^~~~~~~~~
1 error generated.
{'libraries': ['blas', 'blas'], 'library_dirs': ['/usr/lib'], 'include_dirs': ['/usr/local/include']}
{'libraries': ['lapack', 'lapack'], 'library_dirs': ['/usr/lib'], 'language': 'f77'}

If I downgrade to version 2.1.4 I do not have problems.

Thanks.

[enzbus]

This should be fixed now, the whole packaging code has been rewritten and it has smarter ways to detect blas on your system.