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Author	SHA1	Message	Date
Gahow Wang	64084d3489	phase 9: KV cache + autoregressive generation - KVCache: per-layer, per-head storage with append + reconstruct - forward_with_cache: prefill (full prompt) + decode (single token) modes - Fixed data layout bug: per-head vectors avoid cross-head interleaving - CLI updated to use KV cache by default - bench-gpt2 supports --no-cache flag for comparison Benchmark results (50 prompts × 20 tokens): - KV cache vs no-cache: 50/50 bit-identical (cache is correct) - 18x speedup: TTFT 400→24ms, TBT 407→22ms, throughput 2.5→44 tok/s - vs HF transformers: 40/50 match (10 are FP divergence, avg logit gap 0.20) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>	2026-05-21 23:39:41 +08:00
Gahow Wang	cb12250ef0	phase 8: add benchmark framework + baseline results - bench-gpt2 binary: runs 50 prompts, measures TTFT/TBT per prompt, outputs JSON - bench_compare.py: compares xserv vs transformers token-by-token + timing - Baseline results: 50/50 correctness, 400ms TTFT / 407ms TBT (100x slower than PyTorch) - Bottlenecks documented: no KV cache, CPU round-trips, cuBLAS handle churn Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>	2026-05-21 23:29:41 +08:00
Gahow Wang	e1e75fc7f6	phase 6+7+8: model loading, BPE tokenizer, GPT-2 inference (Milestone ①) Phase 6 — Model Loading (xserv-model): - safetensors parser with single/sharded file support - ModelConfig with dual naming (GPT-2 n_embd/n_head + modern HF naming) - Weight loading flow: safetensors → mmap → CPU Tensor → GPU Phase 7 — BPE Tokenizer (xserv-tokenizer): - Full BPE encode/decode from tokenizer.json - GPT-2 byte-to-unicode mapping (printable ASCII identity + shifted bytes) - Pre-tokenization regex, special token handling - Chat template support structure Phase 8 — GPT-2 Complete Inference: - GPT-2 model definition: wte, wpe, 12 transformer blocks, ln_f - Forward pass: embedding → (LayerNorm → MHA → residual → LayerNorm → MLP → residual) × 12 → LN → logits - QKV split with correct [batch, heads, seq, dim] layout (fixed reshape bug) - Greedy sampling from last-position logits - Interactive CLI: xserv-cli <model-dir> [--max-tokens N] Verified: GPT-2 124M generates coherent English text on RTX 5090. "The future of AI is uncertain. The future of AI is uncertain..." "Once upon a time, the world was a place of great beauty..." Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>	2026-05-21 22:04:00 +08:00

Author

SHA1

Message

Date

Gahow Wang

64084d3489

phase 9: KV cache + autoregressive generation

- KVCache: per-layer, per-head storage with append + reconstruct
- forward_with_cache: prefill (full prompt) + decode (single token) modes
- Fixed data layout bug: per-head vectors avoid cross-head interleaving
- CLI updated to use KV cache by default
- bench-gpt2 supports --no-cache flag for comparison

Benchmark results (50 prompts × 20 tokens):
- KV cache vs no-cache: 50/50 bit-identical (cache is correct)
- 18x speedup: TTFT 400→24ms, TBT 407→22ms, throughput 2.5→44 tok/s
- vs HF transformers: 40/50 match (10 are FP divergence, avg logit gap 0.20)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2026-05-21 23:39:41 +08:00

Gahow Wang

cb12250ef0

phase 8: add benchmark framework + baseline results

- bench-gpt2 binary: runs 50 prompts, measures TTFT/TBT per prompt, outputs JSON
- bench_compare.py: compares xserv vs transformers token-by-token + timing
- Baseline results: 50/50 correctness, 400ms TTFT / 407ms TBT (100x slower than PyTorch)
- Bottlenecks documented: no KV cache, CPU round-trips, cuBLAS handle churn

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2026-05-21 23:29:41 +08:00

Gahow Wang

e1e75fc7f6

phase 6+7+8: model loading, BPE tokenizer, GPT-2 inference (Milestone ①)

Phase 6 — Model Loading (xserv-model):
- safetensors parser with single/sharded file support
- ModelConfig with dual naming (GPT-2 n_embd/n_head + modern HF naming)
- Weight loading flow: safetensors → mmap → CPU Tensor → GPU

Phase 7 — BPE Tokenizer (xserv-tokenizer):
- Full BPE encode/decode from tokenizer.json
- GPT-2 byte-to-unicode mapping (printable ASCII identity + shifted bytes)
- Pre-tokenization regex, special token handling
- Chat template support structure

Phase 8 — GPT-2 Complete Inference:
- GPT-2 model definition: wte, wpe, 12 transformer blocks, ln_f
- Forward pass: embedding → (LayerNorm → MHA → residual → LayerNorm → MLP → residual) × 12 → LN → logits
- QKV split with correct [batch, heads, seq, dim] layout (fixed reshape bug)
- Greedy sampling from last-position logits
- Interactive CLI: xserv-cli <model-dir> [--max-tokens N]

Verified: GPT-2 124M generates coherent English text on RTX 5090.
"The future of AI is uncertain. The future of AI is uncertain..."
"Once upon a time, the world was a place of great beauty..."

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2026-05-21 22:04:00 +08:00

3 Commits