Creating an Index

All VSAG indexes are built through vsag::Factory::CreateIndex(name, build_params_json). The name selects the implementation; build_params_json configures dimension, metric, and index-specific options.

Supported Index Types

Name	Description	Page	Example
`hgraph`	Improved graph index with richer quantization options	HGraph	`examples/cpp/103_index_hgraph.cpp`
`ivf`	Inverted file with quantization	IVF	`examples/cpp/106_index_ivf.cpp`
`sindi`	Sparse-vector index (e.g. BM25, SPLADE)	SINDI	`examples/cpp/109_index_sindi.cpp`
`pyramid`	Multi-tenant / tag-partitioned graph index	Pyramid	`examples/cpp/107_index_pyramid.cpp`
`brute_force`	Exact exhaustive search; useful as baseline	—	`examples/cpp/105_index_brute_force.cpp`
`hnsw`	Classic HNSW graph index (deprecated — prefer `hgraph`)	—	`examples/cpp/101_index_hnsw.cpp`
`diskann`	Memory-disk hybrid (deprecated — prefer `ivf`)	—	`examples/cpp/102_index_diskann.cpp`

Common Top-Level Fields

Field	Values	Notes
`dim`	positive integer	Fixed after build
`dtype`	`float32` / `fp16` / `bf16` / `int8`	Public API currently uses `float32`
`metric_type`	`l2` / `ip` / `cosine`	Must match at query time

Examples

HNSW

std::string params = R"(
{
    "dim": 128,
    "dtype": "float32",
    "metric_type": "l2",
    "hnsw": {
        "max_degree": 32,
        "ef_construction": 400
    }
}
)";
auto index = vsag::Factory::CreateIndex("hnsw", params).value();

HGraph with FP16 quantization

HGraph uses index_param as the build-time sub-object (hgraph is reserved for search-time parameters like ef_search). See examples/cpp/103_index_hgraph.cpp.

std::string params = R"(
{
    "dim": 768,
    "dtype": "float32",
    "metric_type": "ip",
    "index_param": {
        "base_quantization_type": "fp16",
        "max_degree": 32,
        "ef_construction": 400
    }
}
)";
auto index = vsag::Factory::CreateIndex("hgraph", params).value();

See Index Parameters for the full reference.