问题
I have an AMD cpu and I'm trying to run some code that uses Intel-MKL. The code is significantly slower than I expected.
When you have an AMD CPU, can you speed up code that uses the Intel-MKL? How?
回答1:
Yes you can speed up your code. Set the environment variable MKL_DEBUG_CPU_TYPE=5
then run your code.
FYI this slow down affects anything that uses Intel-MKL library and runs on AMD CPU (i.e. affects all operating systems and affects all programming languages and all programs (older versions of Matlab, C, C++, Python, Anaconda-Python, Machine-Learning like Tensorflow and Pytorch , again anything that uses Intel-MKL library on AMD CPU)).
FYI Setting and getting environment variables is out of scope for this question but here are some helpful links:
- for Windows and another link with screenshots
- personally i do: "old" control panel --> system --> advanced --> environment variables --> system variables --> ceate new
- for Linux here is a general guide
- for the simple case of a
bash
user who wants to set the environment variable just for their own user append the lineexport MKL_DEBUG_CPU_TYPE=5
to your user's.bashrc
file
- for the simple case of a
p.s.
regarding the question "why/how does setting an environment variable cause code to run significantly faster?"
- The default behavior is for the Intel-MKL to check the CPU and run slower code if non-intel is detected.
- Setting the environment variable overrides the default behavior and causes the faster code to execute despite not having Intel hardware.
You are probably wondering "why would Intel have a software slow-down in their MKL library?
- Intel for many years had their compiled code check the CPU first then if the CPU was detected as non-intel the code would choose to run slower code
- there was a lawsuit
- a result of the lawsuit was that Intel had to disclose what they were doing but did not have to stop what they were doing
- here's the wiki page with more history and information: https://en.wikipedia.org/wiki/Intel_C%2B%2B_Compiler#Reception
来源:https://stackoverflow.com/questions/63174453/when-you-have-an-amd-cpu-can-you-speed-up-code-that-uses-the-intel-mkl