Function load_fp8_var_builder

cake-core/src/utils/fp8.rs:138–157

Create a VarBuilder that transparently dequantizes FP8 weights. # Safety Inherits the mmap safety requirements from `MmapedSafetensors`.

(
    filenames: &[std::path::PathBuf],
    dtype: DType,
    device: &Device,
)

///
/// Inherits the mmap safety requirements from `MmapedSafetensors`.
pub unsafe fn load_fp8_var_builder<'a>(
    filenames: &[std::path::PathBuf],
    dtype: DType,
    device: &Device,
) -> anyhow::Result<VarBuilder<'a>> {
    let inner = MmapedSafetensors::multi(filenames)?;

    let fp8_count = inner
        .tensors()
        .iter()
        .filter(|(_, v)| v.dtype() == safetensors::tensor::Dtype::F8_E4M3)
        .count();
    log::info!(
        "FP8 model detected: {} tensors will be dequantized at load time",
        fp8_count
    );

    let backend: Box<dyn SimpleBackend> = Box::new(Fp8Backend { inner });
    Ok(VarBuilder::from_backend(backend, dtype, device.clone()))
}

// ─── Fp8Linear: reusable FP8-aware Linear layer ─────────────────────────────