Windows-dev: grouped quantization + mixed precision + expert budget + download tool

Consolidates all experiment branches into one Windows-dev branch:

1. Group-scaled int4 (fmt=4, gs=128) — glm.c
   - QT struct: added gs field
   - matmul_i4_grouped: AVX2 kernel, verified to 3e-08 vs f32
   - Format detection: auto-detects from .qs scale array size
   - expert_load: both mmap and slab+pread paths handle fmt=4
   - qt_bytes: fmt=4 case added

2. Per-tensor-type mixed precision — convert_fp8_to_int4.py
   - Split classify() into sh/o/kvb/attn/dmlp sub-types
   - New args: --shared-bits, --o-bits, --kvb-bits, --attn-bits, --dmlp-bits
   - Plan: shared expert + o_proj + kv_b_proj at int8, rest grouped int4
   - Only +5.3 GB RAM vs +0 for pure int4

3. EXPERT_BUDGET (miss-aware) — glm.c
   - Caps distinct experts per layer across batch-union
   - Always keeps cache hits, only drops misses
   - Up to 1.8x faster decode on low-RAM hosts

4. Two-step shared-expert prediction (PILOT_TWO) — glm.c
   - la_predict kind==2 + pilot_prefetch integration
   - +3.1% recall over baseline PILOT

5. FP8 download tool — download_fp8.py
   - ModelScope + HuggingFace dual-source
   - Parallel shard download with stall recovery

6. Tiny model generation — make_glm_oracle.py
   - Generated and tested locally for pipeline validation

c/tools/make_glm_bench_model.py

@@ -3,15 +3,27 @@
 This is not a useful language model. It preserves the real glm_moe_dsa data
 flow while remaining small enough to generate locally and run repeated CPU/CUDA
 A/B tests without downloading the 379 GB checkpoint.
+
+With --fp8 the weights are written as FP8 e4m3 + 128x128 block scale_inv, in the
+SAME layout as the real GLM-5.2-FP8 checkpoint, so convert_fp8_to_int4.py can
+exercise its FP8->int4 dequant path on a local fixture (its dims are 128-friendly,
+so this is also the right fixture for --group-size 128 testing):
+
+  python tools/make_glm_bench_model.py --fp8 --output glm_bench_fp8
+  python tools/convert_fp8_to_int4.py --indir glm_bench_fp8 --outdir glm_bench_i4 --ebits 4 --group-size 128
 """
 
 import argparse
 import json
+import sys
 from pathlib import Path
 
 import torch
 from transformers import GlmMoeDsaConfig, GlmMoeDsaForCausalLM
 
+sys.path.insert(0, str(Path(__file__).resolve().parent))   # importa glm_fp8_emit se lanciato da c/
+from glm_fp8_emit import save_fp8_safetensors
+
 
 def build_config() -> GlmMoeDsaConfig:
     return GlmMoeDsaConfig(
@@ -51,6 +63,9 @@ def main() -> None:
     parser.add_argument("--output", default="glm_bench_medium")
     parser.add_argument("--device", default="cuda" if torch.cuda.is_available() else "cpu")
     parser.add_argument("--seed", type=int, default=1234)
+    parser.add_argument("--fp8", action="store_true",
+                        help="write weights as FP8 e4m3 + 128x128 block scale_inv (same layout as "
+                             "GLM-5.2-FP8) instead of bf16, so convert_fp8_to_int4.py can dequant+requant")
     args = parser.parse_args()
 
     torch.manual_seed(args.seed)
@@ -70,7 +85,16 @@ def main() -> None:
     output = Path(args.output)
     output.mkdir(parents=True, exist_ok=True)
     params = sum(p.numel() for p in model.parameters())
-    model.save_pretrained(output, safe_serialization=True, max_shard_size="4GB")
+    if args.fp8:
+        n_fp8, n_tot = save_fp8_safetensors(model.state_dict(), output / "model.safetensors")
+        # save_pretrained scrive config.json; nel path FP8 lo bypassiamo, quindi lo scriviamo
+        # a mano (serve al converter e al motore C). EN: save_pretrained writes config.json;
+        # the FP8 path bypasses it, so write it manually (converter + C engine need it).
+        (output / "config.json").write_text(json.dumps(cfg.to_dict()))
+        print(f"saved FP8: {n_fp8} e4m3 tensors (+{n_tot - n_fp8} scale_inv sidecars / f32) "
+              f"-> {output / 'model.safetensors'}")
+    else:
+        model.save_pretrained(output, safe_serialization=True, max_shard_size="4GB")
 
     model.to(args.device)
     prompt = [3, 14, 159, 26, 53, 58, 200, 11, 77, 240, 5, 99]
@@ -89,6 +113,7 @@ def main() -> None:
         "seed": args.seed,
         "parameters": params,
         "parameters_billions": round(params / 1e9, 4),
+        "format": "fp8-e4m3-128" if args.fp8 else "bf16",
         "purpose": "backend benchmark fixture; random weights, not a language model",
     }
     (output / "bench_manifest.json").write_text(json.dumps(manifest, indent=2))