--promote-failures: reroute with the connections that failed moved first

Each round routes every connection that has failed so far ahead of the
rest, which keep their order. The promoted set only grows, so two groups
cannot take turns failing; the best round is kept.

.gitignore

@@ -20,3 +20,7 @@ htmlcov/
 # Editor / OS
 .DS_Store
 *.swp
+
+# Benchmark inputs and results: board lists name local, often private, designs
+/bench/boards*.txt
+/bench/results/

bench/bench.py

@@ -0,0 +1,206 @@
+"""Route boards under several connection orders and compare variants fairly.
+
+One routing run says little: which connection routes first moves a result by
+ten connections either way on a crowded board. This runs every board with
+every variant under the same seeds (``--seed``), so variant A and variant B
+face the same order on seed 3, and compares them seed by seed.
+
+    uv run python bench/bench.py BOARDS -v base= -v hist1="--history-cost 1" \\
+        --seeds 6 --jobs 4 --out bench/results/hist.jsonl
+
+BOARDS is a text file, one board per line: a name, a DSN path and any flags
+that board always needs, e.g.
+
+    sense  /path/to/charge-sense.dsn  --edge-clearance 0.5
+    # comments and blank lines are ignored
+
+A variant is ``NAME=FLAGS``, or ``NAME@SRC=FLAGS`` to run the code under SRC
+(a worktree's ``src`` directory) rather than the installed package. The first
+variant is the baseline. Results are appended to --out as JSON lines, and runs
+already in it are skipped, so an interrupted benchmark picks up where it left
+off. Exits non-zero if any run crashed or timed out.
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import math
+import os
+import re
+import shlex
+import subprocess
+import sys
+import tempfile
+import threading
+import time
+from concurrent.futures import ThreadPoolExecutor, as_completed
+from pathlib import Path
+
+NOT_ROUTED = re.compile(r"freeroute: (\d+) connection\(s\) not routed")
+TO_ZONE = re.compile(r"freeroute: (\d+) more connection\(s\) left to a zone fill")
+
+
+def parse_boards(path: Path) -> list[tuple[str, Path, list[str]]]:
+    boards = []
+    for line in path.read_text().splitlines():
+        words = shlex.split(line, comments=True)
+        if not words:
+            continue
+        if len(words) < 2:
+            raise SystemExit(f"{path}: want 'name path [flags]', got {line!r}")
+        dsn = Path(words[1]).expanduser()
+        if not dsn.is_file():
+            raise SystemExit(f"{path}: no such DSN {dsn}")
+        boards.append((words[0], dsn, words[2:]))
+    return boards
+
+
+def parse_variant(spec: str) -> tuple[str, str | None, list[str]]:
+    head, sep, flags = spec.partition("=")
+    if not sep or not head:
+        raise SystemExit(f"variant {spec!r}: want NAME=FLAGS or NAME@SRC=FLAGS")
+    name, _, src = head.partition("@")
+    if src and not (Path(src) / "freeroute").is_dir():
+        raise SystemExit(f"variant {name}: {src} has no freeroute package")
+    return name, src or None, shlex.split(flags)
+
+
+def run_one(board, variant, seed: int, timeout: float) -> dict:
+    name, dsn, board_flags = board
+    vname, src, flags = variant
+    env = dict(os.environ)
+    if src:
+        env["PYTHONPATH"] = src + os.pathsep + env.get("PYTHONPATH", "")
+    with tempfile.TemporaryDirectory() as tmp:
+        cmd = [
+            sys.executable, "-m", "freeroute.cli", str(dsn), "-do", f"{tmp}/out.ses",
+            *board_flags, *flags, "--seed", str(seed),
+        ]
+        start = time.monotonic()
+        proc = subprocess.Popen(
+            cmd, env=env, stdout=subprocess.DEVNULL, stderr=subprocess.PIPE, text=True
+        )
+        expired = threading.Event()
+
+        def expire() -> None:
+            expired.set()
+            proc.kill()
+
+        timer = threading.Timer(timeout, expire)
+        timer.start()
+        err = proc.stderr.read()
+        # reap it here rather than through Popen, to keep its peak memory
+        _, wstatus, usage = os.wait4(proc.pid, 0)
+        timer.cancel()
+        proc.returncode = os.waitstatus_to_exitcode(wstatus)
+        proc.stderr.close()
+        status = "timeout" if expired.is_set() else (
+            "ok" if proc.returncode == 0 else f"exit {proc.returncode}"
+        )
+        rss_mb = round(usage.ru_maxrss / 1024)
+        secs = round(time.monotonic() - start, 1)
+    missing = NOT_ROUTED.search(err)
+    zone = TO_ZONE.search(err)
+    return {
+        "board": name, "variant": vname, "seed": seed, "status": status,
+        "unrouted": int(missing.group(1)) if missing else 0,
+        "to_zone": int(zone.group(1)) if zone else 0,
+        "secs": secs, "rss_mb": rss_mb,
+        "tail": err.strip().splitlines()[-1] if status != "ok" and err.strip() else "",
+    }
+
+
+def mean_sd(xs: list[float]) -> tuple[float, float]:
+    m = sum(xs) / len(xs)
+    sd = math.sqrt(sum((x - m) ** 2 for x in xs) / (len(xs) - 1)) if len(xs) > 1 else 0.0
+    return m, sd
+
+
+def report(rows: list[dict], boards, variants) -> None:
+    ok = {(r["board"], r["variant"], r["seed"]): r for r in rows if r["status"] == "ok"}
+    base = variants[0][0]
+    print(f"\nunrouted per board (lower is better), baseline {base!r}\n")
+    print(f"{'board':14} {'variant':14} {'n':>3} {'mean':>6} {'sd':>5} {'min':>4} {'max':>4}"
+          f" {'secs':>6}   vs baseline, seed by seed")
+    for bname, _, _ in boards:
+        for vname, _, _ in variants:
+            runs = sorted((k[2], r) for k, r in ok.items() if k[:2] == (bname, vname))
+            if not runs:
+                print(f"{bname:14} {vname:14}   no finished runs")
+                continue
+            xs = [r["unrouted"] for _, r in runs]
+            m, sd = mean_sd(xs)
+            t, _ = mean_sd([r["secs"] for _, r in runs])
+            line = (f"{bname:14} {vname:14} {len(xs):>3} {m:>6.1f} {sd:>5.1f} {min(xs):>4}"
+                    f" {max(xs):>4} {t:>6.0f}")
+            if vname != base:
+                diffs = [r["unrouted"] - ok[(bname, base, s)]["unrouted"]
+                         for s, r in runs if (bname, base, s) in ok]
+                if diffs:
+                    dm, dsd = mean_sd(diffs)
+                    se = dsd / math.sqrt(len(diffs)) if len(diffs) > 1 else float("inf")
+                    better = sum(d < 0 for d in diffs)
+                    worse = sum(d > 0 for d in diffs)
+                    # a difference inside two standard errors is not a finding
+                    verdict = ("better" if dm < 0 else "worse") if abs(dm) > 2 * se else "no clear change"
+                    line += (f"   {dm:+.1f} ± {se:.1f}  ({better} better, {worse} worse,"
+                             f" {len(diffs) - better - worse} same)  {verdict}")
+            print(line)
+    failed = [r for r in rows if r["status"] != "ok"]
+    for r in failed:
+        print(f"FAILED {r['board']} {r['variant']} seed {r['seed']}: {r['status']} {r['tail']}")
+
+
+def main(argv: list[str] | None = None) -> int:
+    ap = argparse.ArgumentParser(description=__doc__.split("\n\n")[0])
+    ap.add_argument("boards", type=Path, help="board list: name, DSN path, flags")
+    ap.add_argument("-v", "--variant", action="append", required=True,
+                    help="NAME=FLAGS or NAME@SRC=FLAGS; the first is the baseline")
+    ap.add_argument("--seeds", type=int, default=6, help="orders per board and variant")
+    ap.add_argument("--first-seed", type=int, default=0)
+    ap.add_argument("--jobs", type=int, default=4, help="runs at once")
+    ap.add_argument("--timeout", type=float, default=1800, help="seconds per run")
+    ap.add_argument("--out", type=Path, required=True, help="JSON lines, appended")
+    ap.add_argument("--report-only", action="store_true", help="summarise --out, run nothing")
+    args = ap.parse_args(argv)
+
+    boards = parse_boards(args.boards)
+    variants = [parse_variant(v) for v in args.variant]
+    if len({v[0] for v in variants}) != len(variants):
+        raise SystemExit("variant names must differ")
+    seeds = range(args.first_seed, args.first_seed + args.seeds)
+
+    rows: list[dict] = []
+    if args.out.exists():
+        rows = [json.loads(line) for line in args.out.read_text().splitlines() if line.strip()]
+    done = {(r["board"], r["variant"], r["seed"]) for r in rows if r["status"] == "ok"}
+    todo = [(b, v, s) for b in boards for v in variants for s in seeds
+            if (b[0], v[0], s) not in done]
+
+    if not args.report_only and todo:
+        args.out.parent.mkdir(parents=True, exist_ok=True)
+        print(f"{len(todo)} runs, {args.jobs} at a time", file=sys.stderr)
+        # retried runs replace their earlier failure
+        rows = [r for r in rows if (r["board"], r["variant"], r["seed"]) in done]
+        with ThreadPoolExecutor(args.jobs) as pool, args.out.open("w") as out:
+            for r in rows:
+                out.write(json.dumps(r) + "\n")
+            futures = [pool.submit(run_one, b, v, s, args.timeout) for b, v, s in todo]
+            for n, fut in enumerate(as_completed(futures), 1):
+                r = fut.result()
+                rows.append(r)
+                out.write(json.dumps(r) + "\n")
+                out.flush()
+                print(f"[{n}/{len(todo)}] {r['board']} {r['variant']} seed {r['seed']}:"
+                      f" {r['status']} unrouted {r['unrouted']} ({r['secs']}s,"
+                      f" {r['rss_mb']} MB)", file=sys.stderr)
+
+    wanted = {(b[0], v[0], s) for b in boards for v in variants for s in seeds}
+    rows = [r for r in rows if (r["board"], r["variant"], r["seed"]) in wanted]
+    report(rows, boards, variants)
+    return 1 if any(r["status"] != "ok" for r in rows) or len(rows) < len(wanted) else 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

src/freeroute/cli.py

@@ -19,6 +19,7 @@ import argparse
 import sys
 
 from freeroute.dsn.reader import parse_dsn
+from freeroute.route.orders import best_of_orders, promote_failures
 from freeroute.route.pipeline import (
     build_exact_routing_result,
     build_rooms_routing_result,
@@ -29,8 +30,8 @@ from freeroute.ses import write_ses
 #: which optional flags each engine actually implements. Anything not listed for
 #: an engine is rejected by :func:`_validate` rather than quietly ignored.
 ENGINE_OPTIONS: dict[str, frozenset[str]] = {
-    "grid": frozenset({"rip_up", "max_passes"}),
-    "exact": frozenset({"shove", "diagonal", "rip_up", "max_passes"}),
+    "grid": frozenset({"rip_up", "max_passes", "seed", "orders", "promote"}),
+    "exact": frozenset({"shove", "diagonal", "rip_up", "max_passes", "seed", "orders", "promote"}),
     "room": frozenset({"shove", "pack"}),
 }
 
@@ -41,6 +42,9 @@ _FLAG_NAMES = {
     "diagonal": "--diagonal",
     "rip_up": "--no-rip-up",
     "max_passes": "-mp/--max-passes",
+    "seed": "--seed",
+    "orders": "--orders",
+    "promote": "--promote-failures",
 }
 
 
@@ -133,6 +137,33 @@ def build_parser() -> argparse.ArgumentParser:
         help="copper to board-edge clearance in mm, e.g. KiCad's min_copper_edge_clearance "
         "(the DSN does not carry it); default 0: copper only has to stay inside the outline",
     )
+    parser.add_argument(
+        "--seed",
+        type=int,
+        metavar="N",
+        help="grid and exact engines: shuffle the order connections are routed in; "
+        "the same seed gives the same result (default: fewer-pin nets first)",
+    )
+    parser.add_argument(
+        "--orders",
+        type=int,
+        metavar="N",
+        help="grid and exact engines: route N connection orders in parallel and keep the "
+        "one leaving the fewest connections unrouted (the default order is one of them)",
+    )
+    parser.add_argument(
+        "--promote-failures",
+        type=int,
+        metavar="R",
+        help="grid and exact engines: up to R rounds, each routing the connections that "
+        "failed so far first; keeps the best round",
+    )
+    parser.add_argument(
+        "--jobs",
+        type=int,
+        metavar="J",
+        help="processes for --orders (default: one per order, up to the CPU count)",
+    )
     return parser
 
 
@@ -152,6 +183,9 @@ def main(argv: list[str] | None = None) -> int:
             ("diagonal", args.diagonal),
             ("rip_up", args.no_rip_up),
             ("max_passes", args.max_passes is not None),
+            ("seed", args.seed is not None),
+            ("orders", args.orders is not None),
+            ("promote", args.promote_failures is not None),
         )
         if asked
     ]
@@ -173,29 +207,54 @@ def main(argv: list[str] | None = None) -> int:
     rip_up = not args.no_rip_up
     max_passes = args.max_passes if args.max_passes is not None else 10
 
+    if args.orders is not None and args.orders < 1:
+        parser.error("--orders must be at least 1")
     if args.engine == "exact":
-        result = build_exact_routing_result(
-            dsn,
-            layers=layers,
-            shove=args.shove,
-            diagonal=args.diagonal,
-            rip_up=rip_up,
-            max_passes=max_passes,
-            edge_clearance_mm=args.edge_clearance,
-            resolution=2 if args.grid_resolution is None else args.grid_resolution,
-            heuristic_weight=args.heuristic_weight,
-        )
-    elif args.engine == "room":
+        options = {
+            "layers": layers,
+            "shove": args.shove,
+            "diagonal": args.diagonal,
+            "rip_up": rip_up,
+            "max_passes": max_passes,
+            "edge_clearance_mm": args.edge_clearance,
+            "resolution": 2 if args.grid_resolution is None else args.grid_resolution,
+            "heuristic_weight": args.heuristic_weight,
+        }
+    elif args.engine == "grid":
+        options = {
+            "layers": layers,
+            "rip_up": rip_up,
+            "max_passes": max_passes,
+            "edge_clearance_mm": args.edge_clearance,
+            "resolution": 1 if args.grid_resolution is None else args.grid_resolution,
+        }
+    if args.engine == "room":
         result = build_rooms_routing_result(
             dsn, layers=layers, shove=args.shove, pack=args.pack,
             edge_clearance_mm=args.edge_clearance,
         )
-    else:
-        result = build_routing_result(
-            dsn, layers=layers, rip_up=rip_up, max_passes=max_passes,
-            edge_clearance_mm=args.edge_clearance,
-            resolution=1 if args.grid_resolution is None else args.grid_resolution,
+    elif args.promote_failures and args.promote_failures > 1:
+        if args.orders:
+            parser.error("--orders and --promote-failures cannot be combined")
+        result, rounds = promote_failures(
+            dsn_text, args.engine, options, rounds=args.promote_failures, seed=args.seed
         )
+        counts = ", ".join(str(m) for m, _z in rounds)
+        print(f"freeroute: {len(rounds)} rounds, unrouted {counts}; kept the best", file=sys.stderr)
+    elif args.orders and args.orders > 1:
+        result, kept, tried = best_of_orders(
+            dsn_text, args.engine, options, orders=args.orders, seed=args.seed, jobs=args.jobs
+        )
+        counts = ", ".join(f"{'default' if s is None else s}: {m}" for s, (m, _z) in tried)
+        print(
+            f"freeroute: tried {len(tried)} orders, kept "
+            f"{'the default order' if kept is None else f'--seed {kept}'} (unrouted {counts})",
+            file=sys.stderr,
+        )
+    elif args.engine == "exact":
+        result = build_exact_routing_result(dsn, seed=args.seed, **options)
+    else:
+        result = build_routing_result(dsn, seed=args.seed, **options)
 
     ses_text = write_ses(dsn, result)
     missing = [u for u in result.unrouted if not u[3]]

src/freeroute/route/exact_router.py

@@ -94,6 +94,8 @@ def route_board_exact(
     edge_clearance: int | None = None,
     resolution: int = 1,
     heuristic_weight: float = 1.0,
+    seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> ExactRouteResult:
     """Route ``board`` orthogonally and verify the result with exact geometry.
 
@@ -122,6 +124,8 @@ def route_board_exact(
         edge_clearance=edge_clearance,
         resolution=resolution,
         heuristic_weight=heuristic_weight,
+        seed=seed,
+        route_first=route_first,
     )
     edge = 0 if edge_clearance is None else edge_clearance
     outline = board.outline

src/freeroute/route/grid_router.py

@@ -28,6 +28,7 @@ from __future__ import annotations
 
 import heapq
 import math
+import random
 
 from freeroute.board.board import BasicBoard
 from freeroute.board.items import ConductionArea, ObstacleArea, Pin
@@ -154,8 +155,15 @@ class GridRouter:
         edge_clearance: int | None = None,
         resolution: int = 1,
         heuristic_weight: float = 1.0,
+        seed: int | None = None,
+        route_first: frozenset | None = None,
     ) -> None:
         self.board = board
+        # None keeps the deterministic order; a seed shuffles which connection
+        # routes first, to measure how much a result owes to the order
+        self.seed = seed
+        # connections, as (net_no, one end, other end), to route before the rest
+        self.route_first = frozenset(route_first or ())
         # how far (in cells) an escape stub may run to leave a walled-in pin
         self._escape_cells = 12
         self._crowded_cache: dict = {}
@@ -819,9 +827,16 @@ class GridRouter:
         best_count = -1
         best_snapshot: list[tuple[int, list, list]] | None = None
         best_unrouted = len(conns)
+        # conns[i].index == i is what rip-up relies on, so shuffle a view
+        order = list(conns)
+        if self.seed is not None:
+            random.Random(self.seed).shuffle(order)
+        if self.route_first:
+            # stable: the promoted keep their order among themselves, as do the rest
+            order.sort(key=lambda c: (c.net_no, *_ends_of(c)) not in self.route_first)
         for _ in range(passes):
             changed = False
-            for conn in conns:  # deterministic: connection creation order
+            for conn in order:
                 if conn.routed:
                     continue
                 if self._try_route(conn, conns):
@@ -1050,6 +1065,8 @@ def route_board(
     edge_clearance: int | None = None,
     resolution: int = 1,
     heuristic_weight: float = 1.0,
+    seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> RouteResult:
     """Convenience wrapper: build a :class:`GridRouter` and route the board."""
     router = GridRouter(
@@ -1065,5 +1082,7 @@ def route_board(
         edge_clearance=edge_clearance,
         resolution=resolution,
         heuristic_weight=heuristic_weight,
+        seed=seed,
+        route_first=route_first,
     )
     return router.route()

src/freeroute/route/orders.py

@@ -0,0 +1,98 @@
+"""Route one board in several connection orders at once and keep the best.
+
+Which connection routes first moves the result on a crowded board by several
+connections either way, and no single order wins everywhere. Routing a few
+orders in parallel processes and keeping the one that leaves the fewest
+connections unrouted costs cores, not wall time.
+
+Without a seed the candidates are the default order and seeds 0 to N-2, so the
+result is never worse than a plain run. With seed S they are seeds S to S+N-1.
+Ties go to the earlier candidate, so the choice is deterministic.
+"""
+
+from __future__ import annotations
+
+from concurrent.futures import ProcessPoolExecutor
+import os
+
+from freeroute.dsn import parse_dsn
+from freeroute.ses import RoutingResult
+
+from .pipeline import build_exact_routing_result, build_routing_result
+
+
+def candidate_seeds(orders: int, seed: int | None = None) -> list[int | None]:
+    orders = max(int(orders), 1)
+    if seed is None:
+        return [None, *range(orders - 1)]
+    return list(range(seed, seed + orders))
+
+
+def score(result: RoutingResult) -> tuple[int, int]:
+    """Connections left open, then those left to a zone fill: lower is better."""
+    missing = sum(1 for u in result.unrouted if not u[3])
+    return missing, len(result.unrouted) - missing
+
+
+def route_once(dsn_text: str, engine: str, options: dict, seed: int | None) -> RoutingResult:
+    dsn = parse_dsn(dsn_text)
+    if engine == "exact":
+        return build_exact_routing_result(dsn, seed=seed, **options)
+    if engine == "grid":
+        return build_routing_result(dsn, seed=seed, **options)
+    raise ValueError(f"routing orders are not supported by the {engine} engine")
+
+
+def best_of_orders(
+    dsn_text: str,
+    engine: str,
+    options: dict,
+    *,
+    orders: int,
+    seed: int | None = None,
+    jobs: int | None = None,
+) -> tuple[RoutingResult, int | None, list[tuple[int | None, tuple[int, int]]]]:
+    """Route ``orders`` orders and return the best result, the seed that made
+    it (None for the default order), and every candidate's seed and score."""
+    seeds = candidate_seeds(orders, seed)
+    if len(seeds) == 1:
+        result = route_once(dsn_text, engine, options, seeds[0])
+        return result, seeds[0], [(seeds[0], score(result))]
+    jobs = max(1, min(jobs or os.cpu_count() or 1, len(seeds)))
+    with ProcessPoolExecutor(jobs) as pool:
+        futures = [pool.submit(route_once, dsn_text, engine, options, s) for s in seeds]
+        results = [f.result() for f in futures]
+    scores = [score(r) for r in results]
+    best = min(range(len(seeds)), key=lambda i: (scores[i], i))
+    return results[best], seeds[best], list(zip(seeds, scores, strict=True))
+
+
+def promote_failures(
+    dsn_text: str,
+    engine: str,
+    options: dict,
+    *,
+    rounds: int,
+    seed: int | None = None,
+) -> tuple[RoutingResult, list[tuple[int, int]]]:
+    """Route, then route again with every connection that has failed so far
+    moved to the front, keeping the rest in their order. Returns the best
+    round's result and every round's score.
+
+    The promoted set only grows, so a connection that failed once keeps its
+    early place and two groups cannot take turns failing. Stops early when a
+    round routes everything or fails nothing new."""
+    numbers = {n.name: i + 1 for i, n in enumerate(parse_dsn(dsn_text).nets)}
+    first: frozenset = frozenset()
+    best: RoutingResult | None = None
+    scores: list[tuple[int, int]] = []
+    for _ in range(max(int(rounds), 1)):
+        result = route_once(dsn_text, engine, {**options, "route_first": first}, seed)
+        scores.append(score(result))
+        if best is None or scores[-1] < score(best):
+            best = result
+        failed = {(numbers.get(name), a, b) for name, a, b, zone in result.unrouted if not zone}
+        if not failed or failed <= first:
+            break
+        first = first | failed
+    return best, scores

src/freeroute/route/pipeline.py

@@ -80,6 +80,8 @@ def route_dsn_board(
     layers: list[int] | None = None,
     rip_up: bool = True,
     max_passes: int = 10,
+    seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> tuple[RouteResult, int, list[str]]:
     """Route a parsed :class:`DsnBoard`; return the board-unit result, the scale,
     and the layer names. ``layers`` restricts routing to those signal-layer
@@ -100,6 +102,8 @@ def route_dsn_board(
         layers=layers,
         rip_up=rip_up,
         max_passes=max_passes,
+        seed=seed,
+        route_first=route_first,
     )
     return result, scale, [layer.name for layer in dsn.layers]
 
@@ -140,11 +144,14 @@ def build_routing_result(
     rip_up: bool = True,
     max_passes: int = 10,
     edge_clearance_mm: float | None = None,
+    seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> RoutingResult:
     """Route ``dsn`` (grid track) and convert to a DSN-unit RoutingResult."""
     route, scale, layer_names = route_dsn_board(
         dsn, layers=layers, rip_up=rip_up, max_passes=max_passes,
-        edge_clearance_mm=edge_clearance_mm, resolution=resolution,
+        edge_clearance_mm=edge_clearance_mm, resolution=resolution, seed=seed,
+        route_first=route_first,
     )
     return _to_routing_result(route, dsn, scale, layer_names)
 
@@ -160,6 +167,8 @@ def route_dsn_board_exact(
     rip_up: bool = True,
     shove: bool = False,
     diagonal: bool = False,
+    seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> tuple[ExactRouteResult, int, list[str]]:
     """Route a parsed :class:`DsnBoard` with the exact-geometry (orthogonal,
     DRC-verified) track; return the exact result, the scale, and layer names.
@@ -184,6 +193,8 @@ def route_dsn_board_exact(
         rip_up=rip_up,
         shove=shove,
         diagonal=diagonal,
+        seed=seed,
+        route_first=route_first,
     )
     return exact, scale, [layer.name for layer in dsn.layers]
 
@@ -199,6 +210,8 @@ def build_exact_routing_result(
     rip_up: bool = True,
     max_passes: int = 10,
     edge_clearance_mm: float | None = None,
+    seed: int | None = None,
+    route_first: frozenset | None = None,
 ) -> RoutingResult:
     """Route ``dsn`` (exact track) and convert to a DSN-unit RoutingResult."""
     exact, scale, layer_names = route_dsn_board_exact(
@@ -211,6 +224,8 @@ def build_exact_routing_result(
         edge_clearance_mm=edge_clearance_mm,
         resolution=resolution,
         heuristic_weight=heuristic_weight,
+        seed=seed,
+        route_first=route_first,
     )
     return _to_routing_result(exact.result, dsn, scale, layer_names)
 

tests/route/test_orders.py

@@ -0,0 +1,78 @@
+"""--orders: route several connection orders and keep the best."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from freeroute.cli import main
+from freeroute.route.orders import (
+    best_of_orders,
+    candidate_seeds,
+    promote_failures,
+    route_once,
+    score,
+)
+
+FIXTURES = Path(__file__).resolve().parent.parent / "dsn" / "fixtures"
+# Greedy (no rip-up), the default order strands a net here and seeds 1 to 3 do not.
+RIPUP = (FIXTURES / "ripup_needed.dsn").read_text()
+GREEDY = {"rip_up": False}
+
+
+def test_the_default_order_is_always_a_candidate_without_a_seed():
+    assert candidate_seeds(1) == [None]
+    assert candidate_seeds(4) == [None, 0, 1, 2]
+    assert candidate_seeds(3, seed=7) == [7, 8, 9]
+
+
+def test_keeps_the_order_that_leaves_the_fewest_unrouted():
+    assert score(route_once(RIPUP, "grid", GREEDY, None)) == (1, 0)
+    result, kept, tried = best_of_orders(RIPUP, "grid", GREEDY, orders=3, jobs=2)
+    assert kept == 1
+    assert score(result) == (0, 0)
+    assert tried == [(None, (1, 0)), (0, (1, 0)), (1, (0, 0))]
+
+
+def test_ties_go_to_the_earlier_candidate():
+    # every order routes this board fully, so the default order is kept
+    _, kept, tried = best_of_orders(RIPUP, "grid", {}, orders=3, jobs=3)
+    assert kept is None
+    assert all(s == (0, 0) for _, s in tried)
+
+
+def test_cli_orders_writes_the_best_session(tmp_path, capsys):
+    out = tmp_path / "best.ses"
+    rc = main([str(FIXTURES / "ripup_needed.dsn"), "--no-rip-up", "--orders", "3", "-do", str(out)])
+    assert rc == 0
+    err = capsys.readouterr().err
+    assert "tried 3 orders, kept --seed 1" in err
+    assert "not routed" not in err
+    assert out.read_text().startswith("(session")
+
+
+def test_promoting_the_failed_connection_routes_it():
+    best, rounds = promote_failures(RIPUP, "grid", GREEDY, rounds=3)
+    assert rounds == [(1, 0), (0, 0)]  # stops once nothing fails
+    assert score(best) == (0, 0)
+
+
+def test_nothing_promoted_is_the_plain_order():
+    plain = route_once(RIPUP, "grid", {}, None)
+    empty = route_once(RIPUP, "grid", {"route_first": frozenset()}, None)
+    assert plain == empty
+
+
+def test_cli_promote_failures(tmp_path, capsys):
+    out = tmp_path / "p.ses"
+    rc = main(
+        [
+            str(FIXTURES / "ripup_needed.dsn"),
+            "--no-rip-up",
+            "--promote-failures",
+            "3",
+            "-do",
+            str(out),
+        ]
+    )
+    assert rc == 0
+    assert "2 rounds, unrouted 1, 0" in capsys.readouterr().err

tests/route/test_router.py

@@ -264,6 +264,19 @@ def test_larger_board_still_connects_its_multipin_nets():
     assert len(result.routed_net_numbers) == multi_pin == 4
 
 
+def test_a_seed_is_repeatable_and_does_change_the_order():
+    # The benchmark samples seeds to measure how much a result owes to the
+    # routing order. A seed that changed nothing would make every sample the
+    # same run and report no spread at all.
+    text = (FIXTURES / "kicad_routable.dsn").read_text()
+    default = _wire_key(route_dsn_board(parse_dsn(text))[0])
+    runs = {s: route_dsn_board(parse_dsn(text), seed=s)[0] for s in range(4)}
+    again = route_dsn_board(parse_dsn(text), seed=1)[0]
+    assert _wire_key(again) == _wire_key(runs[1])
+    assert any(_wire_key(r) != default for r in runs.values())
+    assert all(r.unrouted == 0 for r in runs.values())
+
+
 # --- oracle parity ----------------------------------------------------------
 
 

tests/test_cli.py

@@ -154,6 +154,9 @@ def test_cli_supported_combinations_are_accepted(tmp_path):
         "diagonal": ["--diagonal"],
         "rip_up": ["--no-rip-up"],
         "max_passes": ["-mp", "4"],
+        "seed": ["--seed", "3"],
+        "orders": ["--orders", "2"],
+        "promote": ["--promote-failures", "2"],
     }
     for engine, options in ENGINE_OPTIONS.items():
         for option in options:

uv.lock

@@ -128,7 +128,7 @@ wheels = [
 
 [[package]]
 name = "freeroute"
-version = "0.1.0"
+version = "2026.7.14"
 source = { editable = "." }
 
 [package.dev-dependencies]