Unable to import lightgbm after install

Question

My operating system is macOS Sierra, 10.12.5, and I am using Anaconda and python 2.7. After install, and when I try: import lightgbm as lgb I got the following message:

OSError                                   Traceback (most recent call last)
<ipython-input-28-2ae3725bef24> in <module>()
----> 1 import lightgbm as lgb

/Users/tenggao/anaconda/lib/python2.7/site-packages/lightgbm/__init__.py in <module>()
      7 from __future__ import absolute_import
      8 
----> 9 from .basic import Booster, Dataset
     10 from .callback import (early_stopping, print_evaluation, record_evaluation,
     11                        reset_parameter)

/Users/tenggao/anaconda/lib/python2.7/site-packages/lightgbm/basic.py in <module>()
     29 
     30 
---> 31 _LIB = _load_lib()
     32 
     33 

/Users/tenggao/anaconda/lib/python2.7/site-packages/lightgbm/basic.py in _load_lib()
     24     if len(lib_path) == 0:
     25         raise Exception("cannot find LightGBM library")
---> 26     lib = ctypes.cdll.LoadLibrary(lib_path[0])
     27     lib.LGBM_GetLastError.restype = ctypes.c_char_p
     28     return lib

/Users/tenggao/anaconda/lib/python2.7/ctypes/__init__.pyc in LoadLibrary(self, name)
    438 
    439     def LoadLibrary(self, name):
--> 440         return self._dlltype(name)
    441 
    442 cdll = LibraryLoader(CDLL)

/Users/tenggao/anaconda/lib/python2.7/ctypes/__init__.pyc in __init__(self, name, mode, handle, use_errno, use_last_error)
    360 
    361         if handle is None:
--> 362             self._handle = _dlopen(self._name, mode)
    363         else:
    364             self._handle = handle

OSError: dlopen(/Users/tenggao/anaconda/lib/python2.7/site-packages/lightgbm/lib_lightgbm.so, 6): Library not loaded: /usr/local/opt/libiomp/lib/libiomp5.dylib
  Referenced from: /Users/tenggao/anaconda/lib/python2.7/site-packages/lightgbm/lib_lightgbm.so
  Reason: image not found

Thanks in advance for your help.

Answer 1

I have encountered the same issue on my mac, which is fixed by simply installing OpenMP library.

brew install libomp

For any doubt please visit the installation page here

Answer 2

I had the issue as you before. Actually, LightGBM depends on OpenMP for compiling, which isn't supported by Apple Clang. You should install gcc/g++ by using following command:

brew install cmake
brew install gcc --without-multilib

See more details here Hope this can help you.