NGen 0.2 development

NGen generates exact streaming Number Theoretic Transform hardware. Its SGen-style command line lowers finite-field transform specifications through a latency-aware RTL representation and emits synthesizable SystemVerilog, metadata, and optional graphs.

Acyclic datapaths use TimedGraph; stateful streaming designs use the shared MicroProgram IR, which preserves dependency order while packing independent operations into the configured hardware width.

Supported designs

Preset	Configuration	Generated interface
yata8	N=8, K=8, radix 8	dual YATA RAINTT
yata64	N=64, K=8, radix 8	dual YATA RAINTT
yata512	N=512, K=64, radix 8	dual YATA RAINTT
hoge32	N=32, K=32, radix 32	dual HOGE butterfly
hoge1024	N=1024, K=32, radix 32	packed NTTWrap/INTTWrap
kyber256	N=256, one PE	Kyber PE1 load/start/read protocol

Custom NTT-friendly primes support fully-parallel or streamed radix-2 generation at any power-of-two streaming width. Complete cyclic and negacyclic transforms, plus parameterized incomplete negacyclic transforms, share the canonical plan and streamed backend.

Build and use

Java 17 or newer is required.

sbt test assembly
./ngen.bat version
./ngen.bat presets

./ngen.bat -preset yata512 -k 6 -r 3 -profile baseline \
  -o YataRainttTop.v raintt

./ngen.bat -preset hoge1024 -k 5 -r 5 -o INTTWrap.v intt
./ngen.bat -preset hoge1024 -k 5 -r 5 -o NTTWrap.v ntt

./ngen.bat -preset kyber256 -k 0 -r 1 -o KyberHPM1PE.v kyberpe

./ngen.bat -n 3 -k 3 -r 1 -q 17 -root 9 \
  -graph -rtlgraph -o design.sv ntt

./ngen.bat -n 8 -k 3 -r 1 -q 3329 -root auto -base-case 2 \
  -architecture streamed -reduction montgomery -o incomplete.sv ntt

./ngen.bat -n 4 -k 2 -r 1 -q 12289 -root auto \
  -input-order natural -output-order bitreversed -o streamed.sv intt

Options precede the terminal transform. -n, -k, and -r are base-2 logarithms. Pipeline profiles are baseline and f300; the latter adds a scheduling gap between microcoded bundles or uses the deeper generic graph latencies. f300 is a pipeline intent, not a vendor timing guarantee.

For custom domains, -architecture auto|fully-parallel|streamed controls the lowering. auto preserves the fully-parallel v0.1 implementation when K=N and otherwise selects the streamed state machine. Streamed designs expose ready, accept next with the first input chunk, and can overlap a new first chunk with the previous final output chunk. -reduction barrett|montgomery|shoup selects constant modular multiplication. Shoup emits a precomputed reciprocal beside each fixed twiddle and performs one final correction. -root auto discovers an exact-order root; use -root auto -psi auto for complete negacyclic transforms.

-input-order and -output-order accept natural or bitreversed for complete transforms. -base-case <size> selects an incomplete negacyclic transform that stops at polynomial blocks of that size. Higher-radix algebraic fusion is represented and reference-checked in the planner; generic fused RTL emission remains future work, so custom RTL currently requires -r 1.

-transpose indexed preserves the v0.1 compiled-address implementation. -transpose switch uses recursive HOGE SwitchTransposeUnit networks for YATA inverse input/forward output and HOGE inverse input streaming transposes. YATA supports switch transpose in both directions. HOGE currently supports it for intt; forward HOGE requires switches interleaved with the recursive HomGate butterfly pipeline and is rejected instead of silently changing the architecture. The standalone primitive/network can be emitted with:

./ngen.bat -n 3 -data-width 32 -o transpose8.sv switchtranspose

Every generation writes <output-stem>.json. -graph writes the transform decomposition and -rtlgraph writes the scheduled architecture graph.

LLM-NTT adapter

The standalone adapter maps characterized task IDs to NGen commands and the sibling evaluator:

scripts/ngen_llm_ntt.py \
  --task small_yata8x8_raintt_p27 \
  --llm-ntt-root ../LLM-NTT-Examples \
  --transpose switch \
  --with-yosys

Supported task IDs cover all rows in the table above. The adapter does not couple NGen to the LLM candidate-selection runner.

Verification

• Scala models check modular arithmetic, roots, transform decompositions, Kyber's incomplete schedule, timed alignment, and code generation.
• scripts/test_generated_rtl.sh lint-compiles and simulates a generated custom NTT against a known vector.
• scripts/test_switch_transpose.sh verifies an 8-by-8 tagged stream through the recursive switch network, and the Yosys smoke suite includes a switch-backed YATA streaming wrapper.
• scripts/test_streamed_ntt.py generates and simulates randomized cyclic, negacyclic, and incomplete NTT/INTT designs across multiple K, stream orders, pipeline profiles, Barrett/Montgomery/Shoup reductions, and an overlapped back-to-back transaction.
• LLM-NTT-Examples provides TFHEpp/cuHEpp/Kyber vector oracles for every characterized preset, including a standalone HOGE forward-NTT oracle.
• The evaluator's --with-yosys --yosys-candidate-only path records flattened structural statistics for self-contained generated designs.

NGen is GPL-3.0 licensed. Generated designs do not copy checked-in reference RTL; constants and schedules are derived from the declared transform domains.