aaie-moe-pretrain

AAIE-Distilled MoE

A 617.91M-parameter (222.73M active per token) Mixture-of-Experts transformer trained on general web text via knowledge distillation against a Qwen/Qwen2.5-3B teacher. This is the raw base checkpoint — it has not seen any instruction-tuning or task-specific fine-tuning, so it behaves like a classic base language model: it continues text plausibly, but will not reliably follow instructions phrased as questions or requests.

⚠️ This checkpoint is from an unfinished, deliberately-stopped run — read "Training status" below before using this for anything beyond experimentation. For a fully-converged model from this same project, see the companion AAIE-Distilled Dense model instead (dense architecture, same distillation recipe, trained to completion).

Training status — read this first

Training was stopped by request at step 41,860 of a 100,000-step target (41.9%) — this is not a converged model. It was stopped cleanly (not a crash), and validation loss/router health were both stable at the time of stopping, but the model had already been in a noisy, flat validation-perplexity plateau (roughly 17–23 ppl) since around step 20,000, with no clear further improvement through the final checkpoint. See this project's MOE_TRAINING_REPORT.md (or the copy in the training repo root) for the full writeup, including why this plateau is the main open question for anyone continuing this run, and a matched-step comparison against the dense variant showing the two architectures are close enough to be within each other's noise band at this point in training — no confident "MoE beats/loses to dense" claim should be drawn from the current checkpoints.

Also note: this run's teacher (Qwen/Qwen2.5-3B) is larger than the dense sibling model's teacher (Qwen/Qwen2.5-1.5B) — any comparison between the two architectures also carries this confound and isn't a clean architecture-only comparison.

Architecture

Same GQA-attention backbone (8 query heads / 2 KV heads) + RoPE + RMSNorm + tied embeddings as the dense sibling model, but the feed-forward layer is replaced with an 8-expert, top-2-routed Mixture-of-Experts FFN: each token is scored by a router against all 8 experts, sent to its top-2, and those experts' outputs are combined by (renormalized) router weight. Only the selected experts run per token, so compute per token scales with top-2, not all 8.

Two auxiliary losses (load-balancing + router z-loss, Zoph et al. 2022 ST-MoE) plus router-input jitter were used during training to keep routing balanced — the router never collapsed over the full training run (zero collapse warnings, max_expert_frac stayed in the healthy 0.18–0.33 range against a 0.5 warning threshold the entire time). Router jitter is a training-only regularizer and is not part of this exported inference module.

Data

Training settings

Usage

This is a base model — prompt it as a text continuation, not an instruction:

from transformers import AutoModelForCausalLM, AutoTokenizer

repo = "your-username/aaie-moe-pretrain"  # after pushing, see push_to_hub.py
tokenizer = AutoTokenizer.from_pretrained(repo)
model = AutoModelForCausalLM.from_pretrained(repo, trust_remote_code=True, device_map="auto")

inputs = tokenizer("The purpose of a database index is", return_tensors="pt").to(model.device)
out = model.generate(**inputs, max_new_tokens=60, use_cache=True, do_sample=True, temperature=0.8)
print(tokenizer.decode(out[0, inputs["input_ids"].shape[1]:], skip_special_tokens=True))

trust_remote_code=True is required (custom architecture, see modeling_aaiemoe.py). use_cache=True (the default) enables real KV-caching for .generate() — see GQAAttentionCached in modeling_aaiemoe.py. The MoE routing forward pass (MoEFFN) runs per-token top-2 expert selection at every call, same as during training (minus the training-only jitter/aux-loss terms).

Known limitations

• Not converged: stopped at 41.9% of its planned training budget, in the middle of an unresolved validation-perplexity plateau. Expect noisier, less reliable outputs than a fully-trained model of comparable size.
• Not instruction-tuned: asking it a question or giving it an instruction will often just produce a plausible-sounding continuation of the prompt text rather than an answer/response — this is expected base-model behavior on top of being additionally undertrained.
• Qualitative spot-check (LLM-judge, base checkpoint, pre-instruction-tuning) scored this model's outputs lower than the dense sibling's (1.50/10 vs 3.05/10 mean, on a 20-example IT/CS assignment-feedback rubric) — but that comparison used a dense checkpoint trained to full completion against this checkpoint mid-training, so it mostly reflects relative training progress rather than an architecture verdict. See MOE_TRAINING_REPORT.md §5.4 for the full caveat.
• Router health metrics (no collapse, balanced expert usage) were monitored throughout training and were fine at every checkpoint — if you fine-tune this further and see degraded outputs, routing collapse is unlikely to be the cause based on this run's history, but worth re-checking regardless (log max_expert_frac/entropy per forward pass if you do).