### Index Factory Example

Source: https://github.com/facebookresearch/faiss/blob/main/c_api/INSTALL.md

C code demonstrating how to use the faiss_index_factory function.

```c
FaissIndex* index = NULL;
int c = faiss_index_factory(&index, 64, "Flat", METRIC_L2);
if (c) {
    // operation failed
}
```

--------------------------------

### Free Index Example

Source: https://github.com/facebookresearch/faiss/blob/main/c_api/INSTALL.md

C code demonstrating manual memory management for a Faiss index.

```c
faiss_Index_free(index);
```

--------------------------------

### Python Search Example

Source: https://github.com/facebookresearch/faiss/wiki/Getting-started

Demonstrates how to perform k-nearest neighbor search using Faiss in Python, including a sanity check and the actual search.

```python
k = 4                          # we want to see 4 nearest neighbors
D, I = index.search(xb[:5], k) # sanity check
print(I)
print(D)
D, I = index.search(xq, k)     # actual search
print(I[:5])                   # neighbors of the 5 first queries
print(I[-5:])                  # neighbors of the 5 last queries
```

--------------------------------

### PQFastScan Example Build Target

Source: https://github.com/facebookresearch/faiss/blob/main/tutorial/cpp/CMakeLists.txt

Defines a build target for the Product Quantization Fast Scan Faiss example and links it to the faiss library.

```cmake
add_executable(7-PQFastScan EXCLUDE_FROM_ALL 7-PQFastScan.cpp)
target_link_libraries(7-PQFastScan PRIVATE faiss)
```

--------------------------------

### PQFastScanRefine Example Build Target

Source: https://github.com/facebookresearch/faiss/blob/main/tutorial/cpp/CMakeLists.txt

Defines a build target for the Product Quantization Fast Scan Refine Faiss example and links it to the faiss library.

```cmake
add_executable(8-PQFastScanRefine EXCLUDE_FROM_ALL 8-PQFastScanRefine.cpp)
target_link_libraries(8-PQFastScanRefine PRIVATE faiss)
```

--------------------------------

### C++ Search Example

Source: https://github.com/facebookresearch/faiss/wiki/Getting-started

Provides a C++ code snippet for performing k-nearest neighbor search, including a sanity check and the actual search. Note: This is an excerpt, refer to the full code in the Faiss tutorial.

```cpp
    int k = 4;
    {
        idx_t *I = new idx_t[k * 5];
        float *D = new float[k * 5];
        index.search(5, xb, k, D, I);
        printf("I=\n");
        for(int i = 0; i < 5; i++) {
            for(int j = 0; j < k; j++) printf("%5ld ", I[i * k + j]);
            printf("\n");
        }
        ...
        delete [] I;
        delete [] D;
    }
    {
        idx_t *I = new idx_t[k * nq];
        float *D = new float[k * nq];
        index.search(nq, xq, k, D, I);
        ...
    }
```

--------------------------------

### IVFFlat Example Build Target

Source: https://github.com/facebookresearch/faiss/blob/main/tutorial/cpp/CMakeLists.txt

Defines a build target for the IVFFlat Faiss example and links it to the faiss library.

```cmake
add_executable(2-IVFFlat EXCLUDE_FROM_ALL 2-IVFFlat.cpp)
target_link_libraries(2-IVFFlat PRIVATE faiss)
```

--------------------------------

### Get Total Number of Elements

Source: https://github.com/facebookresearch/faiss/blob/main/c_api/INSTALL.md

C code showing how to get the total number of elements in an index.

```c
idx_t ntotal = faiss_Index_ntotal(index);
```

--------------------------------

### Per-SIMD translation unit example (AVX2)

Source: https://github.com/facebookresearch/faiss/blob/main/faiss/docs/simd_dynamic_dispatch_migration.md

Example of a per-SIMD translation unit for AVX2, compiled with -mavx2. It includes the necessary header and defines the specialized function within a COMPILE_SIMD_AVX2 guard.

```cpp
#ifdef COMPILE_SIMD_AVX2
#include "functions.h"
#include <immintrin.h>

template <>
void fvec_madd<SIMDLevel::AVX2>(
        size_t n, const float* a, float bf, const float* b, float* c) {
    // AVX2 intrinsics implementation
}
#endif
```

--------------------------------

### Basic Example Build Target

Source: https://github.com/facebookresearch/faiss/blob/main/tutorial/cpp/CMakeLists.txt

Defines a build target for a basic Faiss example (e.g., 1-Flat) and links it to the faiss library.

```cmake
add_executable(1-Flat EXCLUDE_FROM_ALL 1-Flat.cpp)
target_link_libraries(1-Flat PRIVATE faiss)
```

--------------------------------

### Error Handling Example

Source: https://github.com/facebookresearch/faiss/blob/main/c_api/INSTALL.md

C code illustrating error checking and retrieving error messages.

```c
int c = faiss_Index_add(index, nb, xb);
if (c) {
    printf("%s", faiss_get_last_error());
    exit(-1);
}
```

--------------------------------

### IVFPQ Example Build Target

Source: https://github.com/facebookresearch/faiss/blob/main/tutorial/cpp/CMakeLists.txt

Defines a build target for the IVFPQ Faiss example and links it to the faiss library.

```cmake
add_executable(3-IVFPQ EXCLUDE_FROM_ALL 3-IVFPQ.cpp)
target_link_libraries(3-IVFPQ PRIVATE faiss)
```

--------------------------------

### Multiple GPUs Example Build Target

Source: https://github.com/facebookresearch/faiss/blob/main/tutorial/cpp/CMakeLists.txt

Defines a build target for the multiple GPUs Faiss example and links it to the faiss library.

```cmake
add_executable(5-Multiple-GPUs EXCLUDE_FROM_ALL 5-Multiple-GPUs.cpp)
target_link_libraries(5-Multiple-GPUs PRIVATE faiss)
```

--------------------------------

### Build Demo: IVFPQ Indexing

Source: https://github.com/facebookresearch/faiss/blob/main/INSTALL.md

Compiles the C++ demo for IVFPQ indexing.

```shell
make -C build demo_ivfpq_indexing
```

--------------------------------

### Common translation unit example (Scalar)

Source: https://github.com/facebookresearch/faiss/blob/main/faiss/docs/simd_dynamic_dispatch_migration.md

Example of the common translation unit retaining only the scalar (NONE) specialization and the dispatch wrapper. It includes the base header and defines the scalar implementation and the dispatch function.

```cpp
#include "functions.h"
#include <faiss/impl/simd_dispatch.h>

namespace faiss {

template <>
void fvec_madd<SIMDLevel::NONE>(
        size_t n, const float* a, float bf, const float* b, float* c) {
    for (size_t i = 0; i < n; i++)
        c[i] = a[i] + bf * b[i];
}

void fvec_madd(size_t n, const float* a, float bf, const float* b, float* c) {
    with_simd_level([&]<SIMDLevel SL>() {
        fvec_madd<SL>(n, a, bf, b, c);
    });
}

} // namespace faiss
```

--------------------------------

### GPU Example Build Target

Source: https://github.com/facebookresearch/faiss/blob/main/tutorial/cpp/CMakeLists.txt

Defines a build target for the GPU-accelerated Faiss example and links it to the faiss library.

```cmake
add_executable(4-GPU EXCLUDE_FROM_ALL 4-GPU.cpp)
target_link_libraries(4-GPU PRIVATE faiss)
```

--------------------------------

### Monolithic SIMD (legacy) - Before Conversion

Source: https://github.com/facebookresearch/faiss/blob/main/faiss/docs/simd_dynamic_dispatch_migration.md

Example of a function using monolithic SIMD with preprocessor directives for AVX2.

```cpp
// functions.h
void fvec_madd(size_t n, const float* a, float bf, const float* b, float* c);

// functions.cpp
void fvec_madd(size_t n, const float* a, float bf, const float* b, float* c) {
#ifdef __AVX2__
    // AVX2 implementation
#else
    for (size_t i = 0; i < n; i++)
        c[i] = a[i] + bf * b[i];
#endif
}
```

--------------------------------

### Build environment setup and compilation

Source: https://github.com/facebookresearch/faiss/blob/main/demos/rocksdb_ivf/README.md

Steps to create a conda environment, install dependencies, and compile the RocksDB IVF demo.

```bash
conda create -n rocksdb_ivf
conda activate rocksdb_ivf
conda install pytorch::faiss-cpu conda-forge::rocksdb cmake make gxx_linux-64 sysroot_linux-64
cd ~/faiss/demos/rocksdb_ivf
cmake -B build .
make -C build -j$(nproc)
```

--------------------------------

### CMake configuration for SIMD source files

Source: https://github.com/facebookresearch/faiss/blob/main/faiss/docs/simd_dynamic_dispatch_migration.md

Example of how to add per-SIMD source files to the build system in faiss/CMakeLists.txt.

```cmake
set(FAISS_SIMD_AVX2_SRC
  # ... existing entries ...
  path/to/functions_avx2.cpp        # <-- add
)
set(FAISS_SIMD_AVX512_SRC
  # ... existing entries ...
  path/to/functions_avx512.cpp      # <-- add
)
set(FAISS_SIMD_NEON_SRC
  # ... existing entries ...
  path/to/functions_neon.cpp        # <-- add
)
set(FAISS_SIMD_SVE_SRC
  # ... existing entries ...
  path/to/functions_sve.cpp         # <-- add (if SVE implementation exists)
)
set(FAISS_SIMD_RVV_SRC
  # ... existing entries ...
  path/to/functions_rvv.cpp         # <-- add (if RVV implementation exists)
)
```

--------------------------------

### RefineComparison Example Build Target

Source: https://github.com/facebookresearch/faiss/blob/main/tutorial/cpp/CMakeLists.txt

Defines a build target for the Refine Comparison Faiss example and links it to the faiss library.

```cmake
add_executable(9-RefineComparison EXCLUDE_FROM_ALL 9-RefineComparison.cpp)
target_link_libraries(9-RefineComparison PRIVATE faiss)
```