fhelium.engine.ntt.plans.compact_radix2

Compact radix-2 NTT plan construction.

CompactRadix2NttPlan

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CompactRadix2NttPlan(ckks_config: CkksConfig, *, device: str | int | torch.device | None=None)

Canonical compact forward and inverse standard-residue twiddle rows.

Compact CUDA kernels compute butterfly indices in-kernel and consume one integral [prime, coefficient] twiddle table per transform direction. Prime rows follow ckks_config.moduli exactly; final extent is $N$ and both tables use ckks_config.torch_dtype on device. Construction is functional and the forward and inverse tables do not alias.