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Evandabest
66cea52433
Summary: ## Summary Adds a new Metal compute backend so FAISS can run GPU-accelerated similarity search on Apple Silicon (M1/M2/M3/M4/M5). This is just an initial pr, it introduces the build system integration, core Metal infrastructure, and a working `IndexFlat` with L2 and inner product search. I have some follow up prs with more functionality that I plan to submit. Addresses https://github.com/facebookresearch/faiss/issues/2386 — FAISS currently has no GPU acceleration path on Apple Silicon, forcing CPU-only execution. This Metal backend enables GPU-accelerated search on M-series chips, with follow-up PRs adding IVF indexes, Python bindings, and kernel optimizations. All Metal code lives in a new `faiss/gpu_metal/` directory, keeping `faiss/gpu/` (CUDA/ROCm) completely untouched. The backend is opt-in via `cmake -DFAISS_ENABLE_METAL=ON -DFAISS_ENABLE_GPU=OFF`. ### What's included - **Build system**: New `FAISS_ENABLE_METAL` CMake option. When enabled, requires Apple platform, links Metal/MetalKit/MPS/Foundation frameworks, and builds `libfaiss_metal.a`. Three small additions to root `CMakeLists.txt`. - **MetalResources**: Owns `MTLDevice`, `MTLCommandQueue`, and buffer allocation/deallocation. Mirrors `GpuResources` roles. - **MetalIndex**: Base class for Metal-backed indexes (mirrors `GpuIndex`). Single-device only (device 0). - **MetalIndexFlat**: Flat index storing vectors in an `MTLBuffer`. Supports `add`, `add_with_ids`, `reset`, `search` for both `METRIC_L2` and `METRIC_INNER_PRODUCT`. - **MSL compute kernels**: `l2_squared_matrix`, `ip_matrix` (distance computation), and `topk` (sorted insertion, k ≤ 256). Embedded as a compile-time string in `MetalFlatKernels.mm`. - **Backend abstraction**: `get_num_gpus()`, `index_cpu_to_metal_gpu()`, `index_metal_gpu_to_cpu()`, `StandardMetalResources`, and a `GpuIndexFlat` typedef for API parity. - **Tests**: 8 gtest cases in `TestMetalIndexFlat.mm` — L2/IP search correctness vs CPU `IndexFlat`, `add_with_ids`, reset, empty search, `get_num_gpus`, and CPU↔Metal cloning in both directions. All tests skip gracefully if no Metal device is available. - Python/SWIG bindings ### Planned follow up prs - Larger k support (tiling, heap-based top-k) - IVFFlat, IVFPQ, IVFSQ, BinaryFlat - Kernel optimizations (fused distance+top-k, GEMM-tiled distance, simdgroup/threadgroup parallel selection) ### Build and test ```bash mkdir -p build_metal && cd build_metal cmake .. -DFAISS_ENABLE_METAL=ON -DFAISS_ENABLE_GPU=OFF \ -DBUILD_TESTING=ON -DFAISS_ENABLE_PYTHON=OFF \ -DCMAKE_PREFIX_PATH="/opt/homebrew/opt/libomp;/opt/homebrew" cmake --build . --target faiss_metal TestMetalIndexFlat ctest -R TestMetalIndexFlat ``` > The `mkdir -p` avoids the error if the directory exists, and `-DFAISS_ENABLE_PYTHON=OFF` skips the Python dependency that isn't needed for this PR. Pull Request resolved: https://github.com/facebookresearch/faiss/pull/5144 Reviewed By: alibeklfc Differential Revision: D102284936 Pulled By: mnorris11 fbshipit-source-id: 812fc6ceae251b7b33d25f6861fc37b8d7b475c1
23 lines
615 B
C++
23 lines
615 B
C++
// @lint-ignore-every LICENSELINT
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/**
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* Copyright (c) Meta Platforms, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* Unified name for flat GPU index when Metal backend is built.
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* Include this when using the Metal backend for API parity with
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* faiss::gpu::GpuIndexFlat.
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*/
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#pragma once
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#include <faiss/gpu_metal/MetalIndexFlat.h>
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namespace faiss {
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/// When FAISS is built with Metal backend, GpuIndexFlat is MetalIndexFlat.
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using GpuIndexFlat = gpu_metal::MetalIndexFlat;
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} // namespace faiss
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