c1db188e6a5b17dbd3a9bf64e7ec15e3471c8ceb
6 Commits
| Author | SHA1 | Message | Date | |
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 vh
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dae6ede8e2 |
docs(training-playbook): §4 — when the artifact lies about itself
The playbook covered why a run is SLOW. It did not cover the more expensive
failure: a run that COMPLETES, reports plausible numbers, and is wrong about
itself. Seven of those turned up on the Gemma-4 ERP/RP tune between 08-24 and
08-26 and not one raised an error.
New §4, seven landmines plus a pre-launch checklist:
4.1 a cache key must cover the MEANING of the cached thing. The encode
cache missed the impersonation mask; run 2 would have reused run 1's
unmasked encodings and written impersonation_mask_sha256 into its own
manifest while doing it. No error, no count change, normal loss curve.
4.2 validating a VALUE is not validating the PARAMETER. warmup_ratio was
in range and deleted from transformers 5. Build kwargs as data and
diff the NAMES against the installed signature -- you cannot check the
argument list of a call you have already made.
4.3 record what the run RESOLVED to, never what it requested. Run 1
recorded no attention backend, so an MFU panel profiled the serving
seat under sdpa and recommended adopting flex_attention for a run that
was already using it.
4.4 never train from a dirty tree; harness_commit will name a commit that
does not describe the run. Annotate afterwards, never edit the shipped
artifact -- and state what is NOT wrong, or the note casts doubt on
every field it omits.
4.5 a watchdog whose pgrep pattern appears in its own argv can only ever
return "alive". The inert-gate shape in a liveness check.
4.6 an instrument nobody runs is not an instrument. Mutation-check any
test guarding a property that fails silently.
4.7 fix a stale measurement at the source. "~4.3 HOURS to rebuild the
encode cache" (really 145.5 s) was copied into a new launcher by the
same person who had just measured the real number.
4.8 the pre-launch honesty checklist, ten minutes.
Also:
- Header and framing widened. The file is now a training playbook with a
throughput half and an integrity half; the filename stays for inbound links.
- Sections 4-7 renumbered to 5-8. External refs are all to §1.1 and §3.4 and
are unaffected.
- Four rows added to the superseded-claims table, including the kernel table /
68% quadratic / 8.6% MFU set, which describe the serving seat rather than
the training run.
- gemma4-erp-tune-sizing.md §6 carries a correction banner with the explicit
falls/survives split, because that is the doc someone actually reads before
a run.
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vh
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8de5f7a73c |
docs(gemma4-erp-tune): merged weights are mandatory — vLLM cannot LoRA any Gemma-4
The §5 open question was whether LoRA-on-NVFP4 hot-swap still silently no-ops as it did on vLLM 0.24.0 (#47639), with merged weights as the fallback if it did. Retested on vllm/vllm-openai:latest against the NVFP4A16 base plus the live run's checkpoint adapter. It does not no-op. It refuses to start: AttributeError: To support LoRA for MoE model, 'get_expert_mapping' must be implemented And the reason is bigger than the quant. The check is in vllm/lora/utils.py::process_packed_modules_mapping and branches on whether the model is MoE — quantization is not in the condition. gemma4.py, gemma4_mm.py, gemma4_mtp.py and gemma4_unified.py contain zero occurrences of get_expert_mapping, while deepseek_v2, glm4_moe and ernie45_moe do implement it. So vLLM cannot serve a LoRA on Gemma-4 at all, BF16 or quantized. Merging is not a workaround for a quantization limitation; it is the only path for this architecture. This holds even though the adapter never touches experts — validate_adapter_parameters forbids per-expert params, so all 205 targets are attention and dense MLP. The refusal is about the model being MoE, not about what the adapter targets. Worth recording that the current behaviour is an improvement: a loud refusal beats the 0.24.0 silent no-op, which would ship a base model wearing the tune's name and pass every check that does not compare against base. |
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vh
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7b5fd91d3c |
docs(gemma4-erp-tune): root-cause the 8.6% MFU — attention on Ampere kernels, 29.9% padding
Run-01 was killed at step 19 by operator instruction to root-cause before spending a ~13.9h window. Two independent methods now agree on where the step time went, and neither was the hypothesis the consult panel converged on. Scaling fit (3 points, 2 params, residuals <3ms over an 8x range): A = 6.87e-4 s/token, B = 8.85e-8 s/token^2 quadratic share 20.9% @ w=2048 -> 67.8% @ w=16384 No fixed term was needed, which refutes launch-bound outright. Profiler kernel table (device rows only): attention 22,835.8 ms 65.2% fmha_cutlass*_sm80 dense GEMM 2,774.0 ms 7.9% other 5,739.0 ms 16.4% The attention kernels are sm80 — Ampere-generation CUTLASS running on an sm_120 Blackwell card, with the forward on the gmem fallback tier. That is the mechanism behind 100% SM utilisation at 27 of 304 available TFLOPS. Correctness cleared separately: the sliding mask asserts at max 1024 allowed/row, so the 25 windowed layers were genuinely windowed. The same probe found that right-padding is what pins the 5 global layers to an explicit 4D mask and off the is_causal fast path — measured at 9.4% slower for 24% less loss work at fixed width. The largest available win is not the attention kernel. The corpus is 29.9% padding, and bucket-to-pair + shuffle-to-mix takes it to 0.0% for >=35.5% wall clock, no new dependency, unchanged peak memory. Bucket size turned out not to be a diversity knob — roots per accumulation window are flat across a 256x range, so the global micro-batch shuffle does that work alone and the bucket should be tight. Adds docs/pfi/training-throughput-playbook.md as the durable model-agnostic home (sibling to the quantization playbook), the four probes under scripts/training-probes/ with raw output kept for re-derivation, and a §6 to the sizing doc carrying the Gemma-4-specific numbers and round-2 restart parameters. Measured negatives recorded so they are not re-chased: grouped_mm (0.9% slower, and MoE is only 7.9% of the step), CUDA graphs / torch.compile over the expert loop (no fixed cost to amortise), liger fused CE (~1-3% lever), FA4 on sm_120. Round-1 state preserved: 609MB encode cache, order manifest, truncation report, resume script. No checkpoints — it died at step 19 and the first was due at 100, so the lora_B inert-adapter gate never ran and moves to the restart. |
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vh
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33433e0d1e |
docs(gemma4-erp-tune): replace the estimates with measurements — they were 3x optimistic
Ran the loss path on the real checkpoint on GPU0 with synthetic tokens.
The arithmetic held for parameter counts and was badly wrong for
activation memory.
naive CE bsz1 seq 8192 81.93 GiB
naive CE bsz1 seq16384 OOM
chunked CE bsz1 seq16384 65.66 GiB
chunked CE bsz2 seq16384 79.71 GiB <- the run config
chunked CE bsz4 seq16384 OOM
The marginal cost of an extra 16,384-token sequence is ~14 GiB, not the
~5 GiB estimated: the estimate modelled gradient checkpointing as
storing layer inputs plus a modest recompute peak, and the real MoE
recompute peak with top-8-of-128 routing and its scatter/gather buffers
is far heavier. Dense-model intuition does not size an MoE run.
Two predictions landed exactly — 205 target modules and 74,342,400
trainable params at r64 — which is why the rest of the model of the
thing is still worth trusting.
The headline is that chunked CE at seq 16384 costs 16 GiB less than
naive CE at seq 8192, so chunking is what makes brokkr's 16384
recommendation reachable rather than an optimisation on top of it.
max_seq_len moves 8192 -> 16384 on his truncation finding: the cap
drops 6.2% of samples but 22.4% of tokens, concentrated entirely in
dialogue, which is 60% of the mix.
Also records the four harness changes this required (eitri-smithy
62b556b), including the inert-adapter trap: without
enable_input_require_grads() alongside gradient checkpointing on a
frozen base, no gradient reaches the adapters, every one stays at its
initialisation, and the run completes successfully having learned
nothing.
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vh
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c9943b1507 |
docs(gemma4-erp-tune): whole-card placement — gen moves to GPU1, sec stands down
Operator chose a third placement over the two the sizing offered: rather than train beside gen on GPU0 or on GPU1 in mog-sec's slot, move gen to GPU1 and empty GPU0 completely. The tune gets 95.60 GiB with no co-tenant and gen never goes dark beyond its own restart. Revised run parameters, since a whole card changes them: - micro-batch 8 (71.8 GiB of 95.60) rather than 4, grad-accum 1, giving 888 optimizer steps instead of 444. At one epoch the step count is worth having, and 8 x 8192 tokens puts ~4,096 rows through each expert per step against ~512 at micro-batch 1 — a far healthier GEMM on 704-wide experts. - Gradient checkpointing stays ON. Dropping it takes ~17% off wall-clock but pushes activations to ~24 GiB per sequence, which forces micro-batch 1 and costs 8x on MoE efficiency. Wide beats shallow. - Scriberr stays on GPU1. The previous revision suggested moving it to GPU0, which was correct only while training was going to live on GPU1. Records the ordering constraint in both directions, the elway identity requirement, and that sec's aliases should be allowed to fail at the gateway rather than be substituted with another model. |
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vh
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c507db9ac0 |
docs(gemma4-erp-tune): size the run against the checkpoint — QLoRA is structurally unavailable
The proposed shape was QLoRA r64. It cannot be run as specified. The checkpoint stores each layer's 128 experts as two fused 3-D nn.Parameter tensors (experts.gate_up_proj [128,1408,2816], experts.down_proj [128,2816,704] — no .weight suffix, so they are parameters, not modules). bitsandbytes 4-bit replacement walks nn.Linear only, so 22.84B params / 42.54 GiB — 88.5% of the model — is skipped and stays BF16. load_in_4bit saves ~3.1 GiB of 48.07 and does not error while doing it. Verdict: plain LoRA on BF16, ~57.6 GiB at micro-batch 1, +2.5 GiB per additional 8192-token sequence. Two sizing items were absent from the brief and both are load-bearing: - vocab 262,144 x seq 8,192 = 2.147B logits, with final_logit_softcapping 30.0 adding a saved pre-cap tensor. Naive HF cross-entropy peaks at ~28-30 GiB transient at batch 1, which puts the run at ~85.6 GiB on a 95.6 GiB card — it starts, then OOMs on the first long sample. Fused or chunked linear CE is mandatory and must be smoke-proven before a window is booked, since Liger may not carry a Gemma-4 MoE patch. - v_proj does not exist on layers 5/11/17/23/29 (attention_k_eq_v on the full-attention layers). A v_proj target silently produces no adapter there, and k_proj adapts K and V simultaneously. 45.96M trainable at r64 across q/k/v/o. Placement, measured: GPU0 has 53.46 GiB free beside gen, ~4 GiB short, and gen's footprint grows with uptime. Stopping mog-sec frees 74.29 GiB on GPU1, which holds micro-batch 4 at 61.8 GiB with margin for Scriberr. Recommend standing down sec (2 aliases, last request ~5h ago) rather than gen (7 aliases, 765 busy-engine log lines in 24h). Estimated 1.28e18 FLOPs for the epoch at ~3.67B active params; 4-10 hours at 10-25% MFU. 7,104 packed sequences is only 444 optimizer steps at effective batch 16, which makes the wall-clock-checkpointing amendment concrete rather than hypothetical. Package as a uv venv on /tank: root is 91% full (36 GB) with /var/lib/docker on it. |