topic this is very strange as MKL in Intel® oneAPI Math Kernel Library

Loading MKL 2020 mkl_core.dll resets the DLL search order on Windows

Christoph_Gohlke — Mon, 27 Jan 2020 18:07:54 GMT

Hello,

this issue was reported at <https://github.com/numpy/numpy/issues/15431>

Loading the `mkl_core.dll` from MKL 2020 resets the DLL search order, probably by calling `SetDllDirectoryA(NULL)`.

This breaks any application relying on the DLL search order set by `SetDllDirectory`.

MKL 2019.5 does not reset the DLL search order.

Here's a Python 3.8 script using numpy+mkl and pywin32 demonstrating the issue:

Python 3.8.1 (tags/v3.8.1:1b293b6, Dec 18 2019, 23:11:46) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys, ctypes, win32api
>>> mklpath = sys.prefix + '/Lib/site-packages/numpy/DLLs'
>>> win32api.SetDllDirectory(mklpath)
>>> print(win32api.GetDllDirectory())
X:\Python38/Lib/site-packages/numpy/DLLs
>>> ctypes.CDLL(mklpath + '/mkl_core.dll')
<CDLL 'X:\Python38\Lib\site-packages\numpy\DLLs\mkl_core.dll', handle 7fff323a0000 at 0x11e427c0af0>
>>> print(win32api.GetDllDirectory())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
pywintypes.error: (0, 'GetDllDirectory', 'No error message is available')

this is very strange as MKL

Gennady_F_Intel — Tue, 28 Jan 2020 10:25:36 GMT

this is very strange as MKL themself knows nothing about the python. I would recommend addressing this question to the intel Pyhton Forum - https://software.intel.com/en-us/forums/intel-distribution-for-python

This issue is not specific to

Christoph_Gohlke — Tue, 28 Jan 2020 18:15:18 GMT

This issue is not specific to Python. Python was just used to demonstrate the issue. Here's a C console application that demonstrates the same:

#include <iostream>
#include "windows.h"

int main()
{
    bool b = SetDllDirectoryA((LPCSTR)"C:\\Program Files (x86)\\IntelSWTools\\compilers_and_libraries_2020.0.166\\windows\\redist\\intel64_win\\mkl\\");
    std::cout << "SetDllDirectoryA " << (b ? "succeeded" : "failed") << "\n";

    char buffer[8192];
    DWORD ret = GetDllDirectoryA(8192, buffer);
    std::cout << "GetDllDirectoryA " << ((ret == 0 || GetLastError() != NO_ERROR) ? "failed" : "succeeded") << "\n";
    std::cout << buffer << "\n";

    HINSTANCE hDLL = LoadLibrary((LPCWSTR)L"mkl_core.dll");
    std::cout << "LoadLibrary " << ((hDLL == NULL) ? "failed" : "succeeded") << "\n";

    ret = GetDllDirectoryA(8192, buffer);
    std::cout << "GetDllDirectoryA " << ((ret == 0 || GetLastError() != NO_ERROR) ? "failed" : "succeeded") << "\n";
    std::cout << buffer << "\n";
}

Output:

SetDllDirectoryA succeeded
GetDllDirectoryA succeeded
C:\Program Files (x86)\IntelSWTools\compilers_and_libraries_2020.0.166\windows\redist\intel64_win\mkl\
LoadLibrary succeeded
GetDllDirectoryA failed

Thanks for the update. that's

Gennady_F_Intel — Wed, 29 Jan 2020 03:14:04 GMT

Thanks for the update. that's really interesting and this is the first time we face such an issue. We will check. thanks again.

the quick question - which

Gennady_F_Intel — Wed, 29 Jan 2020 06:14:40 GMT

the quick question - which compiler option do you use to prevent this compile time error: argument of type "LPCWSTR={const WCHAR={__wchar_t} *}" is incompatible with parameter of type "LPCSTR={const CHAR={char} *}"

> which compiler option do

Christoph_Gohlke — Wed, 29 Jan 2020 06:24:15 GMT

> which compiler option do you use to prevent this compile time error

Not sure. I just created a new C++ Console project using Visual Studio 2019.

Try to replace the offending line with:

HINSTANCE hDLL = LoadLibraryA((LPCSTR)"mkl_core.dll");

ok, thanks.

Gennady_F_Intel — Thu, 30 Jan 2020 04:16:02 GMT

ok, thanks.

I have 3 latest versions ( 2018, 2019 and 2020 correspondingly) of MKL installed on my local systems and I see no problems on my part.

.... version 2018.....
SetDllDirectoryA succeeded
GetDllDirectoryA succeeded
C:\Apps\Intel2018\compilers_and_libraries_2018\windows\redist\intel64\mkl\
LoadLibrary succeeded
GetDllDirectoryA succeeded
C:\Apps\Intel2018\compilers_and_libraries_2018\windows\redist\intel64\mkl\

.... version 2019.....
SetDllDirectoryA succeeded
GetDllDirectoryA succeeded
C:\Apps\Intel2019\compilers_and_libraries_2019\windows\redist\intel64\mkl\
LoadLibrary succeeded
GetDllDirectoryA succeeded
C:\Apps\Intel2019\compilers_and_libraries_2019\windows\redist\intel64\mkl\

.... version 2020.....
SetDllDirectoryA succeeded
GetDllDirectoryA succeeded
C:\Apps\Intel2020\compilers_and_libraries_2020\windows\redist\intel64\mkl\
LoadLibrary succeeded
GetDllDirectoryA succeeded
C:\Apps\Intel2020\compilers_and_libraries_2020\windows\redist\intel64\mkl\

one more thing from our side

Gennady_F_Intel — Thu, 30 Jan 2020 04:19:52 GMT

one more thing from our side - the example of the code I used is attached.

compiling: cl test_mkl_loading.cpp

Hi,

Christoph_Gohlke — Thu, 30 Jan 2020 05:59:27 GMT

Hi,

I don't think you can load three different DLLs with the same name. What happens when you load the 2020 version first?

yes, in the case if the only

Gennady_F_Intel — Mon, 03 Feb 2020 06:00:27 GMT

yes, in the case if the only version is called the GetDllDirectoryA() reports the failure

SetDllDirectoryA succeeded
GetDllDirectoryA succeeded
C:\Apps\Intel2020\compilers_and_libraries_2020\windows\redist\intel64\mkl\
LoadLibrary succeeded
GetDllDirectoryA failed

debugging the code under VS

Gennady_F_Intel — Mon, 03 Feb 2020 06:21:35 GMT

debugging the code under VS 2015 - I see the case is passed and the output buffer contains the correct directory...

the issue is escalated and we

Gennady_F_Intel — Tue, 04 Feb 2020 02:52:08 GMT

the issue is escalated and we will keep you informed when the fix of the problem will be available into official build of Intel MKL.

This issue has come up with

Cross__Mat — Tue, 10 Mar 2020 12:46:00 GMT

This issue has come up with some of our customers at NAG. Could you please let us know if there is a timescale for the fix? (Is it expected in 2020.1?)

Thanks.

yes, the expected version is

Gennady_F_Intel — Tue, 10 Mar 2020 13:44:06 GMT

yes, the expected version is MKL 2020.1 and the ERT ~ the beginning of the next month. This thread would be updated.

The fix of the issue

Gennady_F_Intel — Thu, 02 Apr 2020 15:14:21 GMT

The fix of the issue available in MKL 2020 update 1 which available for download.