Add MTP speculative decoding for DeepSeek-V4 - #15
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Implement native MTP support following the HF reference architecture and ml-explore/mlx-lm PR ml-explore#990 patterns: Model (deepseek_v4.py): - MTPBlock wrapping DeepseekV4Block with e_proj, h_proj, enorm, hnorm, norm, and per-block HyperHead - return_hidden support in Model.__call__ for exposing raw 4D hidden state - mtp_forward() and make_mtp_cache() on Model - Weight sanitization: keep and remap MTP weights, stack MTP experts Generation (generate.py): - mtp_generate_step() speculative decoding loop with draft/verify cycle - Greedy exact-match and probabilistic acceptance modes - --mtp CLI flag with graceful fallback warning Server (server.py): - --mtp CLI flag and stream_generate integration
Quantized checkpoints (e.g. 4-bit) typically strip MTP weights to save ~3.2 GB. Detect this in sanitize() and delete self.mtp so the --mtp flag falls back gracefully with a warning.
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jundot
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Wires mlx-lm PR 990 + PR 15 as runtime monkey-patches inside GenerationBatch. oQ preserves mtp.* via a new -mtp suffix; mlx-vlm sanitize is patched to keep MTP norm shift + language_model prefix so quantized VLM checkpoints load with correct per-tensor bits. Source PRs: - mlx-lm#990 (Qwen3.5/3.6 MTP) by AirRunner ml-explore/mlx-lm#990 - mlx-lm fork PR #15 (DeepSeek-V4 MTP) by 0xClandestine Blaizzy/mlx-lm#15
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* feat: port DeepSeek-V4 model + MTP speculative decoding Adds DeepseekV4Model (base model port) and MTPCapable conformance via DeepseekV4MTPBlock, following the same omlx patterns as the Qwen3.5 MTP integration. Registers "deepseek_v4" in LLMTypeRegistry. Source PRs: - mlx-lm base model by Blaizzy, 0xClandestine, angeloskath, pcuenca, eauchs ml-explore/mlx-lm#1192 - mlx-lm fork MTP support by 0xClandestine Blaizzy/mlx-lm#15 * fix: resolve all compilation errors in DeepSeek-V4 port - Replace BaseKVCache subclass with direct KVCache conformance (init/offset/maxSize are not open outside MLXLMCommon) - Rename MultiLinear → DeepseekV4MultiLinear to avoid ambiguity with the identically-named class in GLM4MOELite.swift - Fix .bool_ → .bool and use MLXArray.ones([L,P], dtype: .bool) - Split mixed var/let compound declarations in overlapCompressKV - Fix full(values:) to accept MLXArray(-Float.infinity) - Fix stacked(stacked) → MLX.stacked(stacked) in sanitize - Fix expandedDimensions(axis: [0,1]) → chained single-axis calls - Add @unknown default to SDPA mask switch - MTP: pass layerIdx to DeepseekV4Block init - MTP: pass inputIds to block.callAsFunction - MTP: update createAttentionMask to non-deprecated single-cache API
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Summary
MTPBlockwrapsDeepseekV4Blockwith projection layers (e_proj,h_proj), norms, and per-blockHyperHead— following the HF reference architecturemtp_generate_step()in generate.py implements the draft/verify loop: backbone predicts token t+1, MTP drafts t+2, next backbone step verifies the draft — emitting up to 2 tokens per backbone forward pass--mtpCLI flag for bothgenerateandservercommands, with graceful fallback warning for models without an MTP headReference: ml-explore/mlx-lm#990 (Qwen3.5 MTP pattern)
Test plan
mlx_lm.generate --mtpand confirm speculative decoding produces coherent output--mtpflag on a model without MTP head → confirm fallback warning--mtpflag