--reduce-vias is a last stage: each net that has vias is routed again on
its own with vias made eight times dearer, everything else held as fixed
copper (the window stage's board), and its new copper is kept only if the
net fails nothing new and has fewer vias; the nets with the most vias go
first, within a share of the routing's own time. --via-cost exposes the
search's layer-change price (default 10 grid steps). bench.py records
each run's via count and prints via totals per variant.
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.
--access-cost C makes a route pay C to pass where it would close another
pin's way out (its end cells, the via it may need there, and the
clearance around both) while that pin still has connections to route.
A pin inside a wire keepout can only leave by a via; its stub to the
cell centre was track inside the keepout, which the exact check refused.
The via now goes on the pin itself. Pin stubs are also checked exactly
against wire keepouts, as the exact engine will check them.
bench/diagnose.py reports what each refused connection collided with.
Runs every board with every variant under the same seeds and compares
them seed by seed, so a change is judged against the routing-order
noise rather than one lucky or unlucky run.
rsp2k