FP32 (Baseline)

fp32 stores every coordinate as a 32-bit IEEE-754 float — the same layout as the input vectors. It is the only fully lossless option in VSAG and serves as the reference baseline that all other quantizers are compared against.

Implementation: src/quantization/fp32_quantizer.cpp, parameter file fp32_quantizer_parameter.cpp.

When to use it

• Reorder / precise store. precise_quantization_type: "fp32" is the default precise store when use_reorder: true; the graph walk uses a cheap base quantizer and the top-K candidates are re-scored exactly against the fp32 copy.
• Reference / ground truth. Building an index with base_quantization_type: "fp32" gives the highest possible recall for that index type and is the standard baseline for benchmarking other quantizers (docs/docs/en/src/resources/eval.md).
• Small datasets where memory is not the bottleneck.
• BruteForce with raw-vector retrieval. SUPPORT_GET_RAW_VECTOR_BY_IDS is only advertised when base_quantization_type is fp32 and the metric allows it (src/index/brute_force.cpp).

Memory cost

4 × dim bytes per vector for the codes alone. When fp32 is used as a precise store on top of a base quantizer, the per-vector cost is base codes + 4 × dim.

Parameters

fp32 has no quantizer-specific JSON parameters.

{
    "dtype": "float32",
    "metric_type": "l2",
    "dim": 128,
    "index_param": {
        "base_quantization_type": "fp32",
        "max_degree": 32,
        "ef_construction": 300
    }
}

Training

Not required. fp32 does not set NEED_TRAIN.

Metric compatibility

l2, ip, cosine — all supported with no special handling.

Related pages

• Quantization overview
• HGraph index — see precise_quantization_type
• Memory Management