forked from 1b-agent/fieldcraft-upstream
Christian Svensson
99b0b0cfa4
The D3Q7 scalar lattice steps on the device after the flow's step, in its own A–B pair of buffers: BGK collision with the velocity the momentum collision leaves in the moments buffer, pull streaming with the links' rules read through each group's thermal condition (anti-bounce-back for a held temperature, bounce-back for an adiabatic face, a flux added to the bounced population), inlets at their held temperature and outlets copying their neighbour. The populations are stored as deviations from w_q T₀ so single precision keeps the digits of the differences. The heat each link exchanged goes into the fourth component of the momentum-exchange contributions and the group sums; the buoyant acceleration −β g θ is read per cell in the collision, the open boundaries and the moments. A temperature that stops being a number ends the chunk with Error::Unstable like the flow's checks. Flow exposes what the backend needs to build the device state (the thermal settings and populations). Verification against the CPU on lavapipe: plates held at 20 and 21 (temperatures within 1.4e-5 of the range, the wall heats within 6e-5 and both against k ΔT A / H), a heated channel with a parabolic inlet carrying its temperature, a flux wall, a held wall and an outlet (temperature 3e-7, heat 1e-7) and a buoyant cavity at Ra 10³ (velocity 1.3e-6, temperature 6e-7, heat 2.4e-6). The tests now fail on a shader that does not compile instead of skipping; only a missing device skips. Part of #157.