MiniMax-H3 Ultra Fast

MiniMax-H3 Ultra Fast generates video and synchronized sound locally on one Blackwell ZeroGPU worker. The default 28-step Balanced mode keeps the scheduler quality setting while reducing repeated transformer work.

Modes: Balanced uses FirstBlockCache and long-sequence Sol-Attn; Ultra Fast adds bounded residual forecasting; Exact disables reuse and sparse attention but retains the lossless kernel/layout optimizations. No prompt-to-video result cache is used. A warm 960×544, 56-frame test measured 35s Exact → 23s Balanced (~1.52×).

Optimized from the original multimodalart/minimax-h3 Space. H/t to blanchon for pointing me to NVIDIA Sana/Sol-Engine.

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How the speedups compose

NVFP4 and AdaLN pruning make the entire inference stack fit on one worker, eliminating remote conditioning and per-layer transfers. Fused layouts reduce launches and activation traffic inside every exact block evaluation. FirstBlockCache then removes redundant block-stack evaluations without lowering the requested 28 scheduler steps, while Sol-Attn is enabled only above 24,576 packed tokens where quadratic attention can repay its routing overhead.

The deployed path is benchmark-driven: concurrent VAE decoding, combined AdaLN banks, PyTorch 2.13 and always-on Triton AdaLN kernels were tested but reverted because they were slower, unsupported on ZeroGPU, or too costly at cold start. Video and audio VAEs, normalization, embeddings and output heads remain at higher precision.