huggingface/candle · error

empty codebooks

Error message

empty codebooks

What it means

The quantizer/dequantizer accumulation helper sums per-codebook contributions into an Option<Tensor>; if there were zero codebooks to iterate over, sum stays None and the function bails with 'empty codebooks'. It guarantees the function never silently returns an empty result, but indicates the model config defined no codebooks.

Source

Thrown at candle-transformers/src/models/snac.rs:718

        Ok((z_q, codes))
    }

    #[allow(clippy::wrong_self_convention)]
    fn from_codes(&self, codes: &[&Tensor]) -> Result<Tensor> {
        let mut sum = None;
        for (quantizer, codes) in self.quantizers.iter().zip(codes.iter()) {
            let z_p_i = quantizer.decode_code(codes)?;
            let z_q_i = z_p_i.apply(&quantizer.out_proj)?;
            let z_q_i = repeat_interleave(&z_q_i, quantizer.stride, D::Minus1)?;
            let s = match sum {
                None => z_q_i,
                Some(s) => (s + z_q_i)?,
            };
            sum = Some(s)
        }
        match sum {
            Some(s) => Ok(s),
            None => candle::bail!("empty codebooks"),
        }
    }
}

fn gcd(mut a: usize, mut b: usize) -> usize {
    while b != 0 {
        let t = b;
        b = a % b;
        a = t;
    }
    a
}

fn lcm(a: usize, b: usize) -> usize {
    a / gcd(a, b) * b
}

// https://github.com/hubertsiuzdak/snac/blob/main/snac/snac.py

View on GitHub (pinned to d5fee525bf)

Solutions

1. Verify the SNAC config specifies a positive number of codebooks (e.g. codebook_size/quantizer count > 0)
2. Check VarBuilder checkpoint keys match expected codebook naming so all codebooks load
3. Inspect how the codebooks vector is populated; ensure it is filled before forward is called

Example fix

// before
let quantizer = SnacQuantizer::new(cfg_with_zero_codebooks, vb)?;
// after
assert!(cfg.num_codebooks > 0);
let quantizer = SnacQuantizer::new(cfg, vb)?;

if cfg.num_codebooks == 0 {
    return Err(anyhow::anyhow!("SNAC config must define at least one codebook"));
}

match quantizer.forward(&z) {
    Ok(out) => out,
    Err(e) if e.to_string().contains("empty codebooks") => {
        anyhow::bail!("SNAC quantizer has no codebooks loaded — check checkpoint keys")
    }
    Err(e) => return Err(e.into()),
}

When it happens

Trigger: Calling the forward/dequantize path of the SNAC quantizer with a model whose codebook list is empty (no codebook weights loaded or codebook count 0 in config).

Common situations: Constructing Snac/quantizer from a config with num_quantizers=0; VarBuilder names mismatching so codebook weights are never loaded into the vector; partially initialized model used before loading weights.

Related errors

• SpectralNorm is not supported yet.
• GroupNorm doesn't support causal evaluation.
• pad-mode 'reflect' is not supported
• seanet lstm is not supported
• Not enough audio embeddings: need {}, got {}. Input sequence

AI-assisted analysis of huggingface/candle@d5fee525bf (2026-09-02). Data as JSON: /api/errors/92e882924494a8ab. Report an issue: GitHub.