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rsp2k a6aa1991a1 Rename to rpmroute

The router began as a port of FreeRouting and has grown its own engine
(negotiated congestion, tree nets, exact checks, axis escapes), and
'freeroute' was one letter from the project it no longer follows. The
package, module and command are now rpmroute; the freeroute command stays
as an alias, and the RPMROUTE / RPMROUTE_ORACLE_JAVA variables fall back
to the old FREEROUTE names. Version 2026.10.07. Routing is unchanged: a
PCBench board routes to a byte-identical session either way.

2026-10-07 14:10:36 -06:00

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FreeRouting → Python porting plan

Seed document. The routing agent expands this after studying the upstream Java source. Treat sections marked (TBD from source study) as the first research deliverable.

Ground truth: study the source

Port from the actual FreeRouting Java source, not from the Specctra spec alone. The algorithm details (rip-up-and-retry ordering, cost functions, 45°/free-angle geometry, autoroute vs. optimize passes) live in the code.

# Cloned into ./reference (gitignored — we don't vendor GPL source into history)
git clone --depth 1 https://github.com/freerouting/freerouting reference/freerouting

Key upstream packages to map first (verify paths against the clone):

app/freerouting/designforms/specctra/ — DSN/SES read/write. This is the I/O boundary we must match byte-compatibly enough for kicad-cli to import.
app/freerouting/autoroute/ — the maze/rip-up router core.
app/freerouting/board/ — the routing board data model (items, traces, vias, nets, clearance matrix).
app/freerouting/geometry/planar/ — points, lines, tile shapes, the 45°/free-angle geometry primitives.

The contract (fixed)

Input: Specctra .dsn. Output: Specctra .ses. kicad-cli pcb export specctra-dsn produces the input; kicad-cli pcb import specctra-ses consumes the output. Match that I/O and the rest of kicad-mcp is unchanged.

Phased roadmap

DSN parser — tokenize + parse the S-expression DSN into a typed board model (layers, components, padstacks, nets, keepouts, rules/clearances). First concrete, fully-testable module. Round-trip fixtures from kicad-cli.
SES writer — emit a minimal valid session file KiCad imports cleanly, starting with an empty/no-op route to prove the I/O loop end to end.
Board model + geometry — planar primitives and the item/net/clearance model the router operates on. (TBD from source study.)
Autorouter core — maze routing with rip-up-and-retry. Start grid-based Manhattan/45° for an MVP; converge toward FreeRouting's approach. (TBD.)
Optimize pass — via minimization, trace smoothing. (TBD.)
CLI + kicad-mcp integration — rpmroute board.dsn -o board.ses, then swap it in behind kicad_mcp/utils/freerouting_engine.py's JAR step.

Validation strategy

For any .dsn, FreeRouting's JAR gives a reference .ses. Diff our output against it (connectivity first — every ratsnest resolved — then geometry). The JVM stays available as an oracle during development even though the shipped product has no Java dependency.

Conventions

uv for everything, src-layout, ruff, pytest. Author: Ryan Malloy. Keep modules small and single-purpose. Tests alongside every parser/writer from the first commit.

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