feat(lora): add de-quantized support for fuse.py (#351)

* feat(lora): add de-quantized support for fuse.py

* address comments

lora/fuse.py

@@ -4,6 +4,7 @@ import argparse
 from pathlib import Path
 
 import mlx.core as mx
+import mlx.nn as nn
 import utils
 from mlx.utils import tree_flatten, tree_unflatten
 from models.lora import LoRALinear
@@ -41,6 +42,12 @@ if __name__ == "__main__":
         type=str,
         default=None,
     )
+    parser.add_argument(
+        "-d",
+        "--de-quantize",
+        help="Generate a de-quantized model.",
+        action="store_true",
+    )
 
     print("Loading pretrained model")
     args = parser.parse_args()
@@ -53,7 +60,7 @@ if __name__ == "__main__":
 
     # Freeze all layers other than LORA linears
     model.freeze()
-    for l in model.model.layers[-lora_layers:]:
+    for l in model.model.layers[len(model.model.layers) - lora_layers :]:
         l.self_attn.q_proj = LoRALinear.from_linear(l.self_attn.q_proj)
         l.self_attn.v_proj = LoRALinear.from_linear(l.self_attn.v_proj)
         if hasattr(l, "block_sparse_moe"):
@@ -67,7 +74,32 @@ if __name__ == "__main__":
     ]
 
     model.update_modules(tree_unflatten(fused_linears))
+
+    if args.de_quantize:
+        de_quantize_layers = []
+        for n, m in model.named_modules():
+            if isinstance(m, nn.QuantizedLinear):
+                bias = "bias" in m
+                weight = m.weight
+                weight = mx.dequantize(
+                    weight,
+                    m.scales,
+                    m.biases,
+                    m.group_size,
+                    m.bits,
+                ).astype(mx.float16)
+                output_dims, input_dims = weight.shape
+                linear = nn.Linear(input_dims, output_dims, bias=bias)
+                linear.weight = weight
+                if bias:
+                    linear.bias = m.bias
+                de_quantize_layers.append((n, linear))
+
+        model.update_modules(tree_unflatten(de_quantize_layers))
+
     weights = dict(tree_flatten(model.parameters()))
+    if args.de_quantize:
+        config.pop("quantization", None)
     utils.save_model(args.save_path, weights, tokenizer, config)
 
     if args.upload_name is not None:

lora/models/lora.py

@@ -16,7 +16,7 @@ class LoRALinear(nn.Module):
         lora_lin.linear = linear
         return lora_lin
 
-    def to_linear(self):
+    def to_linear(self, de_quantize: bool = False):
         linear = self.linear
         bias = "bias" in linear
         weight = linear.weight
@@ -43,7 +43,7 @@ class LoRALinear(nn.Module):
         if bias:
             fused_linear.bias = linear.bias
 
-        if is_quantized:
+        if is_quantized and not de_quantize:
             fused_linear = nn.QuantizedLinear.from_linear(
                 fused_linear,
                 linear.group_size,

lora/utils.py

@@ -115,11 +115,21 @@ def make_shards(weights: dict, max_file_size_gibibyte: int = 15):
 def save_model(save_dir: str, weights, tokenizer, config):
     save_dir = Path(save_dir)
     save_dir.mkdir(parents=True, exist_ok=True)
-    shards = make_shards(weights)
+
+    shards = make_shards(weights, max_file_size_gibibyte=5)
+    shards_count = len(shards)
+    shard_file_format = (
+        "model-{:05d}-of-{:05d}.safetensors"
+        if shards_count > 1
+        else "model.safetensors"
+    )
+
     for i, shard in enumerate(shards):
-        # TODO use HF file name scheme for simplicity
+        shard_name = shard_file_format.format(i + 1, shards_count)
-        mx.save_safetensors(str(save_dir / f"weights.{i:02d}.safetensors"), shard)
+        mx.save_safetensors(str(save_dir / shard_name), shard)
+
     tokenizer.save_pretrained(save_dir)
+
     with open(save_dir / "config.json", "w") as fid:
         json.dump(config, fid, indent=4)