Packaging details for building against FAISS C++ API

[cjnolet]

The documentation describes that FAISS builds shared & static libraries but these do not appear to end up in the installed Python packaging. Rather, the Python conda packaging only installs the swig-converted artifacts.

If a codebase, dependent on FAISS, is being built against the libfaiss.so and/or libfaiss_gpu.so artifacts, this leaves developers with the option of forcing contributors to build FAISS themselves, or including the libs in the codebase.

Further clarification on the ideal way of packaging against FAISS C++ API's would be ideal.

[mdouze]

Yes, the .o files are combined into libfaiss.a + libgpufaiss.a.
For C++ packaging, they could just be combined into a single .so that depends on CUDA and a CPU BLAS implementation (usually MKL).
The problem is that properly linking with MKL is hard, and CUDA changes at each version. Therefore we have not done a binary distribution so far.

[cjnolet]

Assuming the users build your source before building libraries that depend on it, Would it make sense to have FAISS install the so files into a common directory already on the LD path (e.g. /user/lib64/faiss)?

We would also need to install the include files in /usr/include as well. This would allow other projects to depend on FAISS and just point their users to the FAISS source.

[mdouze]

Absolutely. IMO the proper paths would be

/usr/lib64/faiss.so
/usr/include/faiss/Index.h
/usr/include/faiss/IndexFlat.h
...

I will talk to @beauby on where we can standardize this an if we can distribute a binary package.

[cjnolet]

Sounds good. I certainly don't mind providing a PR.

[cjnolet]

@mdouze @beauby, I'm preparing to get some changes merged in a project that depends on FAISS. Do you have any objections to changing the default libname / includedir in the build to be /usr/lib64 & /usr/include?

[beauby]

@cjnolet The current default values for libdir/includedir come from autoconf (see here). I do not feel strongly about it though, but in the meantime you can do ./configure --libdir=/usr/lib64 --includedir=/usr/include.