feat: add multi-device layer split (--backend "diffusion=cuda0&cuda1")#1734
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A --backend module assignment can now list several devices separated by '&'. The module's transformer blocks are partitioned into contiguous ranges sized proportionally to each device's free memory (minus a fixed compute headroom) and registered with the ModelManager with per-tensor compute backends; the existing allocation/staging/LoRA/residency machinery handles the weights unchanged. The module's graphs execute on a ggml_backend_sched spanning the devices, pinning each node to the device of the most recently consumed weight (view ops are never pinned) and splitting each graph exactly once. Supported for the diffusion and te modules; for te the dominant encoder (t5xxl or the LLM) splits while small sub-runners stay on the main device. Graph-cut segmentation and --stream-layers are disabled for split modules. Adds --list-devices to print the ggml device names accepted by the backend specs. Manual placement only; row/tensor split and auto-fit are follow-ups. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This was referenced Jul 3, 2026
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As per agreed #1470 split, part 1: layer split.
Manual placement only; row/tensor split and auto-fit are follow-ups.
Related Issue / Discussion
#1470