starting ffr-based transient fault sim

README.md

@@ -57,3 +57,34 @@ nix build github:s-holst/benchmark-circuits#picorv32-sky130
 nix build github:s-holst/benchmark-circuits#jpeg_core-sky130
 ```
 
+## Transient Fault Simulation
+
+Goal: Classify fault effects into: masked, non-SDC, SDC.
+
+- *Transient fault:* A single line-flip fault that is only active for a single clock cycle.
+- *Single line-flip fault:* Logic value on a single signal in the circuit gets inverted. This is equivalent to a stuck-at 0(1) if the fault-free value is 1(0).
+- *Trace length $l$:* Number of clock cycles considered in simulation.
+- *Fault sites $f$:* Number of distict fault locations considered in simulation.
+- Number of distinct faults (size of the fault set) is: $l\cdot f$.
+
+Approach:
+- PPSFP for fault injection cycle. Generates $l\cdot f$ responses (=system states right after fault injection).
+- System states are simulated for the next clock cycles as necessary (fault-free propagation of erroneous states).
+- System states are classified into:
+  - *error-free:* state is the same as in fault-free operation (fault effect disappeared)
+  - *erroneous non-SDC:* surrounding system (testbench) detected the error (criterions: trap signal, OOB memory access, ...)
+  - *erroneous potential-SDC:* state differs from fault-free operation, but remains undetected by surrounding system (testbench).
+- Once a system state becomes *error-free*: Stop further simulation, original fault is *masked*.
+- Once a system state becomes *erroneous non-SDC*: Stop further simulation, original fault is *non-SDC*.
+- As long as system state remains *erroneous potential-SDC*, keep simulating until the end of the trace.
+- If system state is *erroneous potential-SDC* at the end of the trace: original fault is *SDC*.
+
+Optimizations:
+- FFR: Only explicitly simulate FFR stems, reduce number of responses to $l\cdot \#FFR$.
+- Independent FFR could be simulated together, but system states have to be re-constructed for checking.
+- Distributed computing: Partition over fault universe, worker tasks for erroneous potential-SDC propagation.
+
+Some initial code is in `sim_transient_faults.py`. Run
+```
+uv run sim_transient_faults.py picorv32-sky130 patterns.npy
+```

sim_transient_faults.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env -S uv run
+
+import argparse
+import subprocess
+from pathlib import Path
+
+import numpy as np
+
+from kyupy import log, verilog, batchrange, logic
+from kyupy.logic_sim import LogicSim2V
+from kyupy.techlib import techlib_by_name
+
+def main():
+    parser = argparse.ArgumentParser(description='Transient Fault Simulator.')
+    #parser.add_argument('-o', default=None, help='[path/]stem for output files. default: <circuit name>')
+    parser.add_argument('-t', '--tlib', default='SKY130', help=f'techlib of circuit. default: SKY130, available: {sorted(techlib_by_name.keys())}.')
+    parser.add_argument('netlist', help='gate-level verilog file or nix package to import. See "nix flake show github:s-holst/benchmark-circuits" for available packages.')
+    parser.add_argument('npy', help='npy with imported patterns to simulate.')
+    args = parser.parse_args()
+    args.tlib = techlib_by_name[args.tlib]
+
+    if not (nl_path := Path(args.netlist)).exists(): # fallback to published nix package.
+        nix_cmd = f"nix build github:s-holst/benchmark-circuits#{args.netlist} --print-out-paths --no-link"
+        benchmark_path = Path(subprocess.check_output(nix_cmd.split(), text=True).strip())
+        nl_path = next(benchmark_path.glob("*/nl/*.nl.v"))
+
+    log.info(f'Loading {nl_path.absolute()}')
+    c = verilog.load(nl_path, tlib=args.tlib)
+    c.resolve_tlib_cells(args.tlib)  # resolve every cell into kyupy simulation primitives
+    log.info(c)
+    for kind, cnt in sorted(c.stats.items()):
+        log.info(f'  {kind:10s} {cnt}')
+    trap_loc = c.io_locs('trap')
+    mem_valid_loc = c.io_locs('mem_valid')
+    mem_addr_locs = c.io_locs('mem_addr')
+    log.info(f'{trap_loc=} {mem_valid_loc=} {mem_addr_locs=}')
+
+    fault_sites = []
+    for stem, _ in c.fanout_free_regions():
+        if len(stem.outs) > 0 and stem.outs[0] is not None:
+            fault_sites.append(stem.outs[0])
+    fault_sites = np.array(fault_sites, dtype=np.uint32)
+    np.random.shuffle(fault_sites)
+
+    log.info(f'Number of injection sites (FFR stems): {len(fault_sites)}')
+
+    patterns = np.load(args.npy)
+    patterns = np.array([logic.ZERO, logic.ZERO, logic.ZERO, logic.ONE, logic.ZERO, logic.ONE, logic.ZERO, logic.ONE], dtype=np.uint8)[patterns]  # zero-fill unknowns
+    assert len(patterns) == len(c.s_nodes), 'number of bits in patterns does not match the number of circuit PPIOs.'
+    pcount = patterns.shape[1]
+    log.info(f'Pattern count: {pcount}')
+
+    sim = LogicSim2V(c, sims=min(pcount, 10240))
+    log.info(sim)
+    good = sim.allocate()
+
+    for fault_site in fault_sites[:200]:
+        for bo, bs in batchrange(pcount, sim.sims):
+            #log.info(f'Simulating {bs} patterns @ {bo} ...')
+            sim.s_assign[:, :bs] = patterns[:, bo:bo+bs]
+            sim.s_to_c()
+            sim.c_prop()
+            sim.c_to_s()
+            good[:,:bs] = sim.s_result[:,:bs]
+            sim.c_prop(fault_line=fault_site)
+            sim.c_to_s()
+            error_counts = (sim.s_result[:,:bs] != good[:,:bs]).sum(axis=0)
+            traps = sim.s_result[trap_loc,:bs] == logic.ONE
+            mem_valids = sim.s_result[mem_valid_loc,:bs] == logic.ONE
+            mem_addrs = logic.packbits(sim.s_result[mem_addr_locs,:bs].T, dtype=np.uint32)
+            mem_rom_access = mem_valids & (mem_addrs <= 0xffff)
+            mem_ram_access = mem_valids & (mem_addrs >= 0x20000) & (mem_addrs <= 0x23fff)
+            mem_io_access = mem_valids & (mem_addrs == 0x1000_0000)
+            mem_oob_access = mem_valids & ~mem_rom_access & ~mem_ram_access & ~mem_io_access
+            log.info(f'flips@{fault_site} erroneous={np.sum(error_counts != 0)} traps={np.sum(traps)} oob={np.sum(mem_oob_access)}')
+
+if __name__ == '__main__':
+    main()