Add GPU support to static linking

README.md

@@ -8,20 +8,25 @@
 This project provides Rust bindings to [Faiss](https://github.com/facebookresearch/faiss),
 the state-of-the-art vector search and clustering library.
 
-## Installing as a dependency
+## Installing with dynamic linking
 
-Currently, this crate does not build Faiss automatically for you. The dynamic library needs to be installed manually to your system.
+By default, this crate is dynamically linked with the Faiss library installed in your system,
+so it does not build Faiss automatically for you.
+To build the library yourself:
 
   1. Follow the instructions [here](https://github.com/Enet4/faiss/tree/c_api_head/INSTALL.md#step-1-invoking-cmake)
      to build Faiss using CMake,
      enabling the variables `FAISS_ENABLE_C_API` and `BUILD_SHARED_LIBS`.
      The crate is currently only compatible with version v1.7.2.
      Consider building Faiss from [this fork, `c_api_head` branch](https://github.com/Enet4/faiss/tree/c_api_head),
-     which will contain the latest bindings to the C interface.
+     which will contain the latest supported bindings to the C interface.
      For example:
+
      ```sh
-     cmake -B . -DFAISS_ENABLE_C_API=ON -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Release
+     cmake -B build -DFAISS_ENABLE_C_API=ON -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Release
+     cmake --build build
      ```
+
      This will result in the dynamic library `faiss_c` ("c_api/libfaiss_c.so" on Linux),
      which needs to be installed in a place where your system will pick up
      (in Linux, try somewhere in the `LD_LIBRARY_PATH` environment variable, such as "/usr/lib",
@@ -32,16 +37,35 @@ Currently, this crate does not build Faiss automatically for you. The dynamic li
      as well.
   2. You are now ready to include this crate as a dependency:
 
+     ```toml
+     [dependencies]
+     "faiss" = "0.11.0"
+     ```
+
+If you have built Faiss with GPU support, you can include the "gpu" Cargo feature:
+
+```toml
+[dependencies]
+"faiss" = { version = "0.11.0", features = ["gpu"] }
+```
+
+## Installing with static linking
+
+Alternatively to the above, enable the "static" Cargo feature to let Rust build Faiss for you.
+You will still need the dependencies required to build and run Faiss
+as described in their [INSTALL.md](https://github.com/Enet4/faiss/blob/c_api_head/INSTALL.md#building-from-source),
+namely a compatible C++ compiler and a BLAS implementation.
+
 ```toml
 [dependencies]
-"faiss" = "0.11.0"
+"faiss" = { version = "0.11.0", features = ["static"] }
 ```
 
-If you have built Faiss with GPU support, you can include the "gpu" feature in the bindings:
+Compiling Faiss with GPU support is also possible.
 
 ```toml
 [dependencies]
-"faiss" = {version = "0.11.0", features = ["gpu"]}
+"faiss" = { version = "0.11.0", features = ["static", "gpu"] }
 ```
 
 ## Using

faiss-sys/build.rs

@@ -11,7 +11,11 @@ fn static_link_faiss() {
     cfg.define("FAISS_ENABLE_C_API", "ON")
         .define("BUILD_SHARED_LIBS", "OFF")
         .define("CMAKE_BUILD_TYPE", "Release")
-        .define("FAISS_ENABLE_GPU", "OFF")
+        .define("FAISS_ENABLE_GPU", if cfg!(feature = "gpu") {
+            "ON"
+        } else {
+            "OFF"
+        })
         .define("FAISS_ENABLE_PYTHON", "OFF")
         .define("BUILD_TESTING", "OFF")
         .very_verbose(true);
@@ -32,6 +36,12 @@ fn static_link_faiss() {
     println!("cargo:rustc-link-lib=gomp");
     println!("cargo:rustc-link-lib=blas");
     println!("cargo:rustc-link-lib=lapack");
+    if cfg!(feature = "gpu") {
+        let cuda_path = cuda_lib_path();
+        println!("cargo:rustc-link-search=native={}/lib64", cuda_path);
+        println!("cargo:rustc-link-lib=cudart");
+        println!("cargo:rustc-link-lib=cublas");
+    }
 }
 
 #[cfg(feature = "static")]
@@ -57,3 +67,21 @@ fn link_cxx() {
         println!("cargo:rustc-link-lib={}", cxx);
     }
 }
+
+#[cfg(feature = "static")]
+fn cuda_lib_path() -> String {
+    // look for CUDA_PATH in environment,
+    // then CUDA_LIB_PATH,
+    // then CUDA_INCLUDE_PATH
+    if let Ok(cuda_path) = std::env::var("CUDA_PATH") {
+        return cuda_path;
+    }
+    if let Ok(cuda_lib_path) = std::env::var("CUDA_LIB_PATH") {
+        return cuda_lib_path;
+    }
+    if let Ok(cuda_include_path) = std::env::var("CUDA_INCLUDE_PATH") {
+        return cuda_include_path;
+    }
+
+    panic!("Could not find CUDA: environment variables `CUDA_PATH`, `CUDA_LIB_PATH`, or `CUDA_INCLUDE_PATH` must be set");
+}

faiss-sys/gen_bindings.sh

@@ -1,4 +1,7 @@
-#!/bin/sh
+#!/usr/bin/env sh
+# Generate Rust bindings to the Faiss C API
+#
+# Ensure that the submodule is updated and checked out in the intended revision
 if ! which bindgen > /dev/null; then
     echo "ERROR: `bindgen` not found. Please install using cargo:"
     echo "    cargo install bindgen"
@@ -35,5 +38,4 @@ echo ${cmd}
 ${cmd}
 
 # clean up
-rm -rf faiss
 rm -f c_api.h