fhelium.engine.ntt.plans.indexed_radix2

Indexed radix-2 plan construction.

IndexedRadix2NttPlan

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IndexedRadix2NttPlan(ckks_config: CkksConfig, *, device: str | int | torch.device | None=None)

Radix-2 schedules used by the indexed backend.

Forward and inverse indices have shape [2, logN, N/2]. Expanded twiddles contain only the nontrivial odd lane and have shape [prime, logN, N/2]. No all-one even-lane tensor is allocated. Schedules use torch.int32; standard-residue twiddles use the config's integral dtype. All tensors are on device and prime rows follow ckks_config.moduli exactly. These immutable plan tables do not alias.