ImportError: DLL load failed while importing _pydfti

[JeroenBax]

Hi,

I installed the mkl_fft library via pip, when running my code I get the following error,

ImportError: DLL load failed while importing _pydfti: The specified module could not be found

Does anyone know what can cause this error?
Thanks in advance!

[oleksandr-pavlyk]

@JeroenBax Could you please be more specific? Did you do pip install mkl_fft, or python -m pip install --i https://pypi.anaconda.org/intel/simple -extra-index-url https://pypi.org/simple mkl_fft ?

Do you have MKL library installed in your Python environment as well?

[JeroenBax]

Thanks for the quick reply,
I used the "python -m pip install --i https://pypi.anaconda.org/intel/simple -extra-index-url https://pypi.org/simple mkl_fft" command to download the library, which is installed in my Python environment as well.
The error occurs in the init.py file where ._pydfti is unknown

[oleksandr-pavlyk]

It may happen because, while importing _pydfti native extension the MKL library can not be loaded. Let me try to reproduce this behavior. What version of Python are you using?

[JeroenBax]

Version 3.8.10

[oleksandr-pavlyk]

Using pip 22.1.2 I am getting an error:

(try-mkl-fft) C:\Users\opavlyk>python -m pip install --i https://pypi.anaconda.org/intel/simple -extra-index-url https://pypi.org/simple mkl_fft

Usage:
  C:\Users\opavlyk\Miniconda3\envs\try-mkl-fft\python.exe -m pip install [options] <requirement specifier> [package-index-options] ...
  C:\Users\opavlyk\Miniconda3\envs\try-mkl-fft\python.exe -m pip install [options] -r <requirements file> [package-index-options] ...
  C:\Users\opavlyk\Miniconda3\envs\try-mkl-fft\python.exe -m pip install [options] [-e] <vcs project url> ...
  C:\Users\opavlyk\Miniconda3\envs\try-mkl-fft\python.exe -m pip install [options] [-e] <local project path> ...
  C:\Users\opavlyk\Miniconda3\envs\try-mkl-fft\python.exe -m pip install [options] <archive url/path> ...

ambiguous option: --i (--ignore-installed, --ignore-requires-python, --implementation, --index-url, --install-option, --isolated?)

Correcting that I get another error:

(try-mkl-fft) C:\Users\opavlyk>python -m pip install -i https://pypi.anaconda.org/intel/simple -extra-index-url https://pypi.org/simple mkl_fft
ERROR: xtra-index-url is not a valid editable requirement. It should either be a path to a local project or a VCS URL (beginning with bzr+http, bzr+https, bzr+ssh, bzr+sftp, bzr+ftp, bzr+lp, bzr+file, git+http, git+https, git+ssh, git+git, git+file, hg+file, hg+http, hg+https, hg+ssh, hg+static-http, svn+ssh, svn+http, svn+https, svn+svn, svn+file).
WARNING: There was an error checking the latest version of pip.

[JeroenBax]

Yes, I got indeed the same errors, writing --index-url instead of --i and --extra-index-url instead of -extra-index-url, solves the error

[oleksandr-pavlyk]

It does not for me:

(try-mkl-fft) C:\Users\opavlyk>python -m pip install --index-url https://pypi.anaconda.org/intel/simple -extra-index-url https://pypi.org/simple mkl_fft
ERROR: xtra-index-url is not a valid editable requirement. It should either be a path to a local project or a VCS URL (beginning with bzr+http, bzr+https, bzr+ssh, bzr+sftp, bzr+ftp, bzr+lp, bzr+file, git+http, git+https, git+ssh, git+git, git+file, hg+file, hg+http, hg+https, hg+ssh, hg+static-http, svn+ssh, svn+http, svn+https, svn+svn, svn+file).
WARNING: There was an error checking the latest version of pip.

[JeroenBax]

You should type an extra minus sign before the -extra-index-url. So make it --extra-index-url.
That solved the error for me

[oleksandr-pavlyk]

Please try

python -c "import sysconfig, os, ctypes, glob; mkl_fft_dir = os.path.join(sysconfig.get_path('purelib'), 'mkl_fft'); lib = glob.glob(os.path.join(mkl_fft_dir, '_pydfti*')); print(ctypes.cdll.LoadLibrary(lib[0])) if lib else print('lib was empty')"

For me, it outputs

(try-mkl-fft) C:\Users\opavlyk>python -c "import sysconfig, os, ctypes, glob; mkl_fft_dir = os.path.join(sysconfig.get_path('purelib'), 'mkl_fft'); lib = glob.glob(os.path.join(mkl_fft_dir, '_pydfti*')); print(ctypes.cdll.LoadLibrary(lib[0])) if lib else print('lib was empty')"
<CDLL 'C:\Users\opavlyk\Miniconda3\envs\try-mkl-fft\Lib\site-packages\mkl_fft\_pydfti.cp38-win_amd64.pyd', handle 7ff9110e0000 at 0x26756728880>

This could shed additional light as to why the library fails to import.

[oleksandr-pavlyk]

You should type an extra minus sign before the -extra-index-url. So make it --extra-index-url. That solved the error for me

Thank you, it worked indeed. I will updated README in the repo