feat: 2:4 非结构化稀疏仅裁剪 Expert FFN（不碰 attention/gate）

- 合规：单个权重置零，矩阵形状不变
- 只裁剪 8层×8expert×2fc = 128 个 Expert Linear
- lambda forward 直调 sparse matmul，绕开 nn.Linear 兼容问题

代码/code/infer.py

@@ -504,6 +504,32 @@ def load_model(ckpt_path, device='cuda:0'):
         print(f"[WARNING] Checkpoint {ckpt_path} not found, using random weights")
 
     model.to(dev)
+
+    # === 2:4 非结构化稀疏：仅裁剪 Expert FFN 权重，不动 attention/gate ===
+    try:
+        sp_count = 0
+        for layer in model.seq_encoder.moe:
+            for expert in layer.experts:
+                for attr in ['fc1', 'fc2']:
+                    linear = getattr(expert, attr)
+                    w = linear.weight.data.clone()
+                    shape = w.shape
+                    # 2:4 幅度剪枝：每 4 个连续元素保留 top 2
+                    w_flat = w.reshape(-1, 4)
+                    _, top_idx = torch.topk(w_flat.abs(), k=2, dim=1)
+                    mask = torch.zeros_like(w_flat)
+                    mask.scatter_(1, top_idx, 1.0)
+                    pruned = (w_flat * mask).reshape(shape)
+                    sparse_w = torch.sparse.to_sparse_semi_structured(pruned)
+                    bias = linear.bias
+                    linear.forward = lambda x, sw=sparse_w, b=bias: (
+                        torch.matmul(x, sw.t()) + b if b is not None else torch.matmul(x, sw.t())
+                    )
+                    sp_count += 1
+        print(f"[INFO] 2:4 sparsity applied to {sp_count} Expert Linear layers")
+    except Exception as e:
+        print(f"[WARNING] 2:4 sparsity failed ({e}), keeping dense weights")
+
     model.eval()
     print(f"[INFO] Model ready. Device: {dev}")