Can someone write a step-by-step guide for compiling llama.cpp with openBLAS on Windows?

[Folko-Ven]

It took me an hour, but I couldn't get it to work. Need help. Also, if openBLAS improves performance, even if not much, why it isn't used by default?

[SlyEcho]

I have done this, I'll try to explain.

First, get w64devkit w64devkit-1.18.0.zip

Then, get OpenBLAS OpenBLAS-0.3.23-x64.zip

Put w64devkit somewhere you like, no need to set up anything else like PATH, there is just one executable that opens a shell, from there you can build llama.cpp with make as usual.

Now take the OpenBLAS release and from there copy lib/libopenblas.a into w64devkit/x86_64-w64-mingw32/lib and from include copy all the .h files to w64devkit/x86_64-w64-mingw32/include

make LLAMA_OPENBLAS=1 should work now.

The files are going to be big because of static linking, you can also copy libopenblas.dll.a but then you have to keep the .dll file around where OS can load it.

You can also compile OpenBLAS yourself, for that I recommend the Fortran version of w64devkit.

[SlyEcho]

Is there some kind of error? Are you running from the same w64devkit shell?

You could try building OpenBLAS yourself, it's not that difficult, just make pretty much.

[Folko-Ven]

Yes I use w64devkit.exe, then cd to llama.cpp, then make LLAMA_OPENBLAS=1. Several warnings pop up during build, but nothing suspicious. During startup it just crashes (I use powershell to run it).

[Folko-Ven]

YES!!! I made it work! I deleted libopenblas.dll.a from x86_64-w64-mingw32/lib, compiled with make LLAMA_OPENBLAS=1, and placed libopenblas.dll from OpenBLAS-0.3.23-x64\bin next to main.exe .

[SlyEcho]

If you deleted libopenblas.dll.a then the .dll file should not be needed. main.exe is about 33 megs in size then.
When it's using the .dll, it is around 2.6 megs + 48 megs for the .dll.

There is a way to control this with the LDFLAGS variable to override the makefile:

# static openblas
make -B LLAMA_OPENBLAS=1 LDFLAGS="C:\apps\w64devkit\x86_64-w64-mingw32\lib\libopenblas.a" main
# libopenblas.dll
make -B LLAMA_OPENBLAS=1 LDFLAGS="C:\apps\w64devkit\x86_64-w64-mingw32\lib\libopenblas.dll.a" main

[Folko-Ven]

Oh, I see, I didn't copy the .dll library for the exe that needed it, but I copied it for the one that didn't need it. Shame on me. Thank you for your patience.