Add comprehensive layout and routing engine implementation plan

[akiselev]

Documents the architecture, algorithms, and Rust crate dependencies
for building an automatic schematic layout and routing engine with
force-directed placement, simulated annealing optimization, enhanced
A* routing, rip-up-and-reroute, and spatial indexing.

https://claude.ai/code/session_01TZd5VynRK118MgLDeuj4fu

[Copilot]

Pull request overview

This PR adds comprehensive documentation for implementing an automatic schematic layout and routing engine for Altium Designer documents. The plan outlines a five-phase implementation strategy incorporating force-directed placement, simulated annealing optimization, A* pathfinding with enhancements, rip-up-and-reroute capabilities, and spatial indexing using R*-trees.

Changes:

• Added detailed architecture documentation with module structure and algorithm descriptions
• Documented recommended Rust crate dependencies (petgraph, rstar, pathfinding, argmin, etc.)
• Provided code examples for all major components including force-directed layout, simulated annealing, routing algorithms, and API design
• Included testing strategy, implementation timeline (8 weeks), and references to academic papers

---

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[Copilot]

The wire_length_cost method calls self.get_pins_on_net(net, state) and self.bounding_box(&pins), but these helper methods are not defined in the PlacementCost implementation. These methods should either be declared below the shown methods or their signatures should be documented for completeness.

Suggested change

	/// Collect pin locations for a given net in the current placement state.
	///
	/// This helper is referenced by `wire_length_cost`. It is declared here
	/// to document its expected signature; the concrete implementation is
	/// provided by the placement engine.
	fn get_pins_on_net(
	&self,
	net: &NetId,
	state: &PlacementState,
	) -> Vec<(i32, i32)> {
	unimplemented!("get_pins_on_net is implemented in the placement engine");
	}
	/// Compute axis-aligned bounding box for a set of pin coordinates.
	///
	/// Returns `(min_x, max_x, min_y, max_y)`.
	fn bounding_box(
	&self,
	pins: &[(i32, i32)],
	) -> (i32, i32, i32, i32) {
	unimplemented!("bounding_box is implemented in the placement engine");
	}

[Copilot]

The generate_neighbor function is declared to return PlacementState, but the match expression does not return any values from its arms. Each match arm should return a modified PlacementState, or the function should explicitly construct and return the neighbor state after the match.

Suggested change

	match move_type {
	MoveType::Translate { max_distance } => {
	// Move random component by random offset
	}
	MoveType::Rotate => {
	// Rotate random component 90°
	}
	MoveType::Swap => {
	// Swap positions of two similar-sized components
	}
	MoveType::Mirror => {
	// Mirror component horizontally
	}
	}
	// Start from the current placement and apply a random move to create a neighbor
	let mut neighbor = current.clone();
	match move_type {
	MoveType::Translate { max_distance } => {
	// Move random component by random offset (bounded by `max_distance`)
	// TODO: implement translation logic updating `neighbor`
	}
	MoveType::Rotate => {
	// Rotate random component 90°
	// TODO: implement rotation logic updating `neighbor`
	}
	MoveType::Swap => {
	// Swap positions of two similar-sized components
	// TODO: implement swap logic updating `neighbor`
	}
	MoveType::Mirror => {
	// Mirror component horizontally
	// TODO: implement mirror logic updating `neighbor`
	}
	}
	neighbor

[Copilot]

The route_two_points and successors methods call several helper methods (heuristic, path_to_segments, is_valid_position, move_cost) that are not defined in the shown implementation. These helper methods should either be declared or their signatures should be documented for completeness.

Suggested change

	}
	}
	/// Heuristic cost estimate from `from` to `to` for A* (e.g. Manhattan distance).
	fn heuristic(&self, from: CoordPoint, to: CoordPoint) -> i64 {
	// TODO: Implement an appropriate heuristic (e.g. Manhattan or octile distance)
	unimplemented!()
	}
	/// Convert a list of grid points from the A* path into wire segments.
	fn path_to_segments(&self, points: Vec<CoordPoint>) -> Vec<WireSegment> {
	// TODO: Convert consecutive points into horizontal/vertical wire segments
	unimplemented!()
	}
	/// Check whether `pos` is a valid routing position given the previous position and target.
	fn is_valid_position(&self, pos: CoordPoint, prev: CoordPoint, target: CoordPoint) -> bool {
	// TODO: Enforce design rules, avoid obstacles, keep within sheet bounds, etc.
	unimplemented!()
	}
	/// Cost to move from one grid point to another (may penalize vias, bends, congestion, etc.).
	fn move_cost(&self, from: CoordPoint, to: CoordPoint) -> i64 {
	// TODO: Compute movement cost, possibly higher for bends or longer segments
	unimplemented!()
	}

[Copilot]

The route_steiner method is declared to return Option<Vec<WireSegment>> but the function body only contains comments and does not return any value. This will cause a compilation error. Add a placeholder return like todo!() or None to make it valid Rust code.

Suggested change

	// 3. Add Steiner points at intersections
	// 3. Add Steiner points at intersections
	todo!()

[Copilot]

The RipUpRouter implementation calls several helper methods (try_route_net, find_blocking_nets, select_net_to_rip, try_route_net_by_name) that are not defined. These helper methods should either be declared or their signatures should be documented for completeness.

[Copilot]

The type WireSegmentBounds is used in the SpatialIndex struct but is never defined. This type definition should be included, similar to how ComponentBounds is defined above it.

[Copilot]

In the force calculation loop, the force variable is computed but never actually stored or applied to update the positions. The comment on line 391 says "Store force for later application" but this is never implemented. This incomplete code example could be misleading. Either complete the implementation or add a clearer comment explaining that this is a partial example.

Suggested change

	// Store force for later application
	// NOTE: In a full implementation, store `force` for later application to update positions.

[Copilot]

The generate_neighbor method calls .choose(&mut self.rng) on a Vec, but this requires importing the rand::seq::SliceRandom trait. The code example should include this import at the top of the file for completeness.

[Copilot]

The example code uses CoordPoint and Orientation but these types are not imported. The example should include the necessary imports at the top, such as use altium_format::types::{CoordPoint, Orientation, Coord}; or similar.

[Copilot]

The code assigns different result types to a single result variable: PlacementResult when place_only is true, RoutingResult when route_only is true, and AutoLayoutResult otherwise. Then it tries to access result.components_placed, result.wires_routed, and result.wire_crossings on all types. These fields may not exist on all three result types. Either all result types should have these fields, or the verbose output handling should be conditional based on which operation was performed.

Suggested change

	let result = if self.place_only {
	engine.auto_place(&mut session)?
	} else if self.route_only {
	engine.auto_route(&mut session)?
	} else {
	engine.auto_layout(&mut session)?
	};
	if self.verbose {
	println!("Components placed: {}", result.components_placed);
	println!("Wires routed: {}", result.wires_routed);
	println!("Wire crossings: {}", result.wire_crossings);
	if self.place_only {
	let result = engine.auto_place(&mut session)?;
	if self.verbose {
	println!("Components placed: {}", result.components_placed);
	}
	} else if self.route_only {
	let result = engine.auto_route(&mut session)?;
	if self.verbose {
	println!("Wires routed: {}", result.wires_routed);
	println!("Wire crossings: {}", result.wire_crossings);
	}
	} else {
	let result = engine.auto_layout(&mut session)?;
	if self.verbose {
	println!("Components placed: {}", result.components_placed);
	println!("Wires routed: {}", result.wires_routed);
	println!("Wire crossings: {}", result.wire_crossings);
	}