Paul Hontz 4d0bd56968 Add tools/net_compare.py, which checks that two builds play a network game in step ...

To show that a new build (the x86-64 one, an arm64 one) plays network
games with the i686 Linux build, and to keep checking it. It plays the two
together on the loopback, A hosting and B joining and with --swap the other
way round, each copy with a seeded bot, headless, and compares the per-
second logs of the network test: for every player, the host's view and the
client's at the same tick (positions, aim, vitality, weapons, rounds,
grenades, scores, life), within tolerances taken from how the netcode
predicts and corrects, and the host's drift figure (the previous commit).
It prints PASS, FAIL with the first divergent player, tick and field, or
ERROR, and exits 0, 1 or 2. It needs the retail maps, so it is a local or
self-hosted check: NETCODE.md ("Comparing two builds") describes it, the
log line's format and the calibration; README.md's new Testing section and
AGENTS.md list it. tools/test_net_compare.py tests its judging of logs
without the maps, in CI.

Calibrated with an i686 build against itself, 60-second games both ways
round on bloodgulch, beavercreek, hangemhigh, chillout, prisoner, ratrace,
longest and carousel, up to four games at once: 63 of 64 pass (one copy
crashed, reported as an error), and 12 of 12 with scripted hits and kills
(--events). A build of the same sources whose players run 0.5% or 2%
faster (a change made only for the test, not committed) fails all 16
games, at the first second compared. One whose gravity is 0.5% or 2%
stronger passes: it changes only the ticks in the air, which the drift
cannot tell from what identical builds show; NETCODE.md says so.

(cherry picked from commit 0adc286c6497bffe8edfe297181aa39c2b0bbb8e)

2026-10-20 00:21:59 +13:00

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Add tools/net_compare.py, which checks that two builds play a network game in step

2026-10-20 00:21:59 +13:00