Fault Simulation
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#!/usr/bin/env -S uv run
import argparse
import subprocess
from pathlib import Path
import time
import numpy as np
from kyupy import verilog, bench, log, logic, batchrange
from kyupy.techlib import techlib_by_name, KYUPY
from kyupy.logic_sim import LogicSim2V
from fsim.static import LineRoles, FaultSet
def main():
parser = argparse.ArgumentParser(description='A basic stuck-at fault simulator.')
parser.add_argument('-t', '--tlib', default='SKY130', help=f'Techlib for verilog circuit. Default: SKY130, available: {sorted(techlib_by_name.keys())}.')
parser.add_argument('-p', '--patterns', default=1024, help='Number of random patterns to simulate. Default: 1024.')
parser.add_argument('--seed', type=int, default=42, help='Random seed for reproducibility. Default: 42.')
parser.add_argument('circuit', help='Gate-level verilog, bench, or nix package to import. See available packages: "nix flake show github:s-holst/benchmark-circuits".')
args = parser.parse_args()
args.patterns = int(args.patterns)
args.tlib = techlib_by_name[args.tlib]
if not (circuit_path := Path(args.circuit)).exists(): # fallback to published nix package.
nix_cmd = f"nix build github:s-holst/benchmark-circuits#{args.circuit} --print-out-paths --no-link"
benchmark_path = Path(subprocess.check_output(nix_cmd.split(), text=True).strip())
circuit_path = next(benchmark_path.glob("*/nl/*.nl.v"))
log.info(f'loading {circuit_path} ...')
if circuit_path.name.endswith('.bench'):
c = bench.load(circuit_path)
args.tlib = techlib_by_name['KYUPY']
else:
c = verilog.load(circuit_path, tlib=args.tlib)
stats = {k.replace('__',''): v for k, v in c.stats(args.tlib).items() if k.startswith('__') or k.endswith('put')}
log.info(f'circuit {stats=}')
lr = LineRoles(c, args.tlib)
log.info(f'line role stats={lr.stats}')
fs = FaultSet(c, args.tlib)
log.info(f'fault sites: {len(fs.fault_sites)}')
log.info(f'collapsed stuck-at fault count: {len(fs.saf_equiv_classes)}')
c.resolve_tlib_cells(args.tlib)
ffr_stems = []
for stem, _ in c.fanout_free_regions(KYUPY):
if len(stem.outs) > 0 and stem.outs[0] is not None:
ffr_stems.append(stem.outs[0])
ffr_stems = np.array(ffr_stems, dtype=np.uint32)
log.info(f'FFR count: {len(ffr_stems)}')
sim = LogicSim2V(c, sims=min(args.patterns, 10240))
rng = np.random.default_rng(args.seed)
patterns = rng.choice(
[logic.ZERO, logic.ONE],
size=(sim.s_len, args.patterns),
).astype(np.uint8)
golden = np.zeros_like(patterns)
log.info(f'{sim=}')
sim.simulate(patterns, golden)
log.info(f'golden sim finished.')
syndrome = np.zeros_like(patterns)
injection_faults = np.array(list(fs.saf_equiv_classes.keys()), dtype=np.uint32)
rng.shuffle(injection_faults)
undetected = set()
detected = set()
start_time = time.perf_counter()
with log.progress() as p:
for fidx, fault in enumerate(injection_faults):
fault_site = fault//2
fault_polarity = fault&1
p.update((fidx+1) / len(injection_faults), f'd:{len(detected)} u:{len(undetected)}')
for bo, bs in batchrange(patterns.shape[1], sim.sims):
sim.s_assign[:, :bs] = patterns[:, bo:bo+bs]
sim.s_to_c()
sim.c_prop(fault_line=fault_site, fault_model=fault_polarity)
sim.c_to_s()
syndrome[:, bo:bo+bs] = sim.s_result[:,:bs]
if np.allclose(golden, syndrome):
undetected.add(fault)
else:
detected.add(fault)
sim_time = time.perf_counter() - start_time
log.info(f'fsim time: {sim_time:.2f}s')
sim_performance = stats['comb'] * len(injection_faults) * patterns.shape[1] / sim_time
log.info(f'fsim performance: {sim_performance:.2e} gfp/s')
log.info(f'detected by simulation: {len(detected)}/{len(injection_faults)} - {len(detected)/len(injection_faults)*100:.2f}%')
if __name__ == "__main__":
main()