example_simulate.py

#!/usr/bin/env python3
"""Reproduce any row of `pphilip/analog-circuits-sky130` with ngspice.

Usage
-----
    python example_simulate.py                      # first converged row of train
    python example_simulate.py --split test --row 42
    python example_simulate.py --circuit-id analoggym_amp_yan_az_pin_3_s015
    python example_simulate.py --row 0 --print-spice      # dump the reconstructed SPICE

Every row of the `with_testbench` config carries the exact, ngspice-ready
SPICE that produced its `metrics`. Reproducing a row is:
    1. Load the row.
    2. Substitute `{{SKY130_LIB}}` with your local SKY130 `.lib` path.
    3. Run ngspice on the result.
    4. Parse the `.meas` output.

Prerequisites
-------------
    pip install datasets
    # Install ngspice (v46+):
    #   brew install ngspice          (macOS)
    #   apt install ngspice           (Debian/Ubuntu)
    #   (or build from source: http://ngspice.sourceforge.net/)
    # Install the SkyWater SKY130 PDK (Apache 2.0):
    pip install volare && volare fetch --pdk sky130
    # Point SKY130_LIB at the combined/continuous lib:
    export SKY130_LIB="$(volare show sky130)/sky130A/libs.tech/combined/continuous/sky130.lib.spice"
"""

from __future__ import annotations

import argparse
import json
import os
import shutil
import subprocess
import sys
import tempfile
from pathlib import Path


# ---------------------------------------------------------------------------
# Run ngspice + parse .meas output
# ---------------------------------------------------------------------------

def run_ngspice(spice_text: str) -> tuple[dict[str, float], str]:
    """Run ngspice in batch mode. Returns (parsed_metrics, raw_log).

    ngspice's `ngbehavior=hs` mode lowercases every token, so `.meas`
    labels come back as `dc_gain_db` even if the SPICE source wrote
    `dc_gain_dB`. Parsing is case-insensitive.
    """
    if shutil.which("ngspice") is None:
        raise RuntimeError(
            "ngspice not found on PATH. Install it (see prerequisites above)."
        )
    with tempfile.TemporaryDirectory() as d:
        tb = Path(d) / "tb.spice"
        tb.write_text(spice_text)
        r = subprocess.run(
            ["ngspice", "-b", str(tb)],
            capture_output=True, text=True, timeout=60,
        )
    log = r.stdout + r.stderr

    # `.meas` output looks like:   dc_gain_db          =  -3.07410e+01 at=  1.00000e+00
    metrics: dict[str, float] = {}
    for line in log.splitlines():
        parts = line.strip().split("=", 1)
        if len(parts) != 2:
            continue
        key = parts[0].strip().lower()
        if not key or " " in key:
            continue
        # Take the first numeric token after `=`
        for tok in parts[1].split():
            try:
                metrics[key] = float(tok)
                break
            except ValueError:
                continue
    return metrics, log


def first_reproducible_row(ds) -> int:
    """Return the index of the first converged row with a non-empty testbench_spice.

    `failed` split rows can still carry a testbench_spice (the sim was attempted
    but didn't converge), so testbench-presence alone isn't enough — we also
    require `converged=True` so the shipped `metrics` are meaningful.
    """
    for i in range(len(ds)):
        row = ds[i]
        if row.get("converged") and row.get("testbench_spice"):
            return i
    raise RuntimeError("no converged row with testbench_spice found in this split")


def main() -> int:
    ap = argparse.ArgumentParser(description=__doc__)
    ap.add_argument("--split", default="train",
                    choices=["train", "validation", "test", "failed"])
    ap.add_argument("--row", type=int, default=None,
                    help="Row index within the split (default: first usable row)")
    ap.add_argument("--circuit-id", default=None,
                    help="Alternative to --row: look up by exact circuit_id")
    ap.add_argument("--print-spice", action="store_true",
                    help="Print the reconstructed SPICE and exit without running")
    args = ap.parse_args()

    from datasets import load_dataset
    print(f"Loading pphilip/analog-circuits-sky130 (config: with_testbench, split: {args.split})…")
    ds = load_dataset(
        "pphilip/analog-circuits-sky130",
        "with_testbench",
        split=args.split,
    )

    if args.circuit_id is not None:
        idx = None
        for i, r in enumerate(ds):
            if r["circuit_id"] == args.circuit_id:
                idx = i
                break
        if idx is None:
            print(f"circuit_id {args.circuit_id!r} not in split {args.split!r}",
                  file=sys.stderr)
            return 1
    elif args.row is not None:
        if not 0 <= args.row < len(ds):
            print(f"--row {args.row} out of range (split has {len(ds)} rows)",
                  file=sys.stderr)
            return 1
        idx = args.row
    else:
        idx = first_reproducible_row(ds)

    row = ds[idx]
    shipped = json.loads(row["metrics"]) if row["metrics"] else {}
    spice = row["testbench_spice"]

    print(f"  circuit_id:     {row['circuit_id']}")
    print(f"  topology:       {row['topology']}  (source: {row['source_dataset']})")
    print(f"  shipped metric: dc_gain_dB = {shipped.get('dc_gain_dB', 'n/a')} dB")

    if not spice:
        print("\n  ERROR: this row has no testbench_spice (failed-build case).",
              file=sys.stderr)
        return 1

    if args.print_spice:
        # Show the SPICE verbatim including the {{SKY130_LIB}} placeholder —
        # this path doesn't run ngspice, so a local PDK isn't required.
        print("\n--- reconstructed SPICE ---")
        print(spice)
        return 0

    sky130_lib = os.environ.get("SKY130_LIB")
    if not sky130_lib or not Path(sky130_lib).exists():
        print(
            "ERROR: SKY130_LIB env var not set or doesn't point to a valid file.\n"
            "Install the PDK: `pip install volare && volare fetch --pdk sky130`\n"
            "Then:             `export SKY130_LIB=<path to sky130.lib.spice>` "
            "(combined/continuous variant).",
            file=sys.stderr,
        )
        return 2

    # Swap the portability placeholder for the user's local PDK path.
    spice = spice.replace("{{SKY130_LIB}}", sky130_lib)

    print("\nRunning ngspice…")
    try:
        metrics, log = run_ngspice(spice)
    except RuntimeError as e:
        print(f"ERROR: {e}", file=sys.stderr)
        return 3

    reproduced = metrics.get("dc_gain_db")  # ngspice lowercases output keys
    print(f"  reproduced: dc_gain_dB = {reproduced} dB")

    if reproduced is not None and "dc_gain_dB" in shipped:
        delta = abs(reproduced - shipped["dc_gain_dB"])
        tag = "✓ bit-exact" if delta < 1e-3 else ("~ within 0.1 dB" if delta < 0.1 else "✗ mismatch")
        print(f"  delta:      {delta:.6f} dB  {tag}")

    return 0


if __name__ == "__main__":
    sys.exit(main())