Merge pull request #159 from mistralai/add_lora

Add LoRA

README.md

@@ -233,3 +233,6 @@ Instructions to run the image can be found in the [official documentation](https
 - Use Mistral models on [Mistral AI official API](https://console.mistral.ai/) (La Plateforme)
 - Use Mistral models via [cloud providers](https://docs.mistral.ai/deployment/cloud/overview/)
 
+## References
+
+[1]: [LoRA](https://arxiv.org/abs/2106.09685): Low-Rank Adaptation of Large Language Models, Hu et al. 2021

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "mistral_inference"
-version = "v1.0.4"
+version = "v1.1.0"
 description = ""
 authors = ["bam4d <[email protected]>"]
 readme = "README.md"
@@ -24,7 +24,7 @@ exclude = ["docs", "tools", "build"]
 
 [tool.poetry.dependencies]
 python = "^3.9.10"
-xformers = ">=0.0.25"
+xformers = ">=0.0.24"
 simple-parsing = ">=0.1.5"
 fire = ">=0.6.0"
 mistral_common = "^1.0.0"

src/mistral_inference/__init__.py

@@ -1 +1 @@
-__version__ = "1.0.4"
+__version__ = "1.1.0"

src/mistral_inference/lora.py

@@ -0,0 +1,166 @@
+import logging
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Dict, NamedTuple, Union
+
+import safetensors.torch
+import torch
+import torch.nn as nn
+from simple_parsing.helpers import Serializable
+
+
+@dataclass
+class LoraArgs(Serializable):
+    rank: int
+    scaling: float
+
+    def __post_init__(self):
+        assert self.rank > 0
+        assert self.scaling > 0.0
+
+
+class LoRALinear(nn.Module):
+    """
+    Implementation of:
+        - LoRA: https://arxiv.org/abs/2106.09685
+
+    Notes:
+        - Freezing is handled at network level, not layer level.
+        - Scaling factor controls relative importance of LoRA skip
+          connection versus original frozen weight. General guidance is
+          to keep it to 2.0 and sweep over learning rate when changing
+          the rank.
+    """
+
+    def __init__(
+        self,
+        in_features: int,
+        out_features: int,
+        rank: int,
+        scaling: float,
+        bias: bool = False,
+    ):
+        super().__init__()
+
+        self.in_features = in_features
+        self.out_features = out_features
+        assert not bias
+        self.bias = bias
+        self.rank = rank
+        self.scaling = scaling
+
+        self.lora_A = nn.Linear(
+            self.in_features,
+            self.rank,
+            bias=self.bias,
+        )
+        self.lora_B = nn.Linear(
+            self.rank,
+            self.out_features,
+            bias=self.bias,
+        )
+
+        self.linear = nn.Linear(self.in_features, self.out_features, bias=self.bias)
+
+        # make sure no LoRA weights are marked as "missing" in load_state_dict
+        def ignore_missing_keys(m: nn.Module, incompatible_keys: NamedTuple):
+            incompatible_keys.missing_keys[:] = []  # type: ignore
+
+        self.register_load_state_dict_post_hook(ignore_missing_keys)
+
+    def forward(self, x: torch.Tensor):
+        lora = self.lora_B(self.lora_A(x))
+        return self.linear(x) + lora * self.scaling
+
+    def _load_from_state_dict(self, state_dict, prefix, *args, **kwargs):
+        key_name = prefix + "weight"
+
+        # full checkpoint
+        if key_name in state_dict:
+            w_ref = state_dict[key_name]
+
+            # load frozen weights
+            state_dict = {
+                "linear.weight": w_ref,
+                "lora_A.weight": torch.zeros_like(
+                    self.lora_A.weight, device=w_ref.device, dtype=w_ref.dtype
+                ),
+                "lora_B.weight": torch.zeros_like(
+                    self.lora_B.weight, device=w_ref.device, dtype=w_ref.dtype
+                ),
+            }
+            self.load_state_dict(state_dict, assign=True, strict=True)
+
+
+class LoRALoaderMixin:
+    def load_lora(self, lora_path: Union[Path, str], scaling: float = 2.0):
+        """Loads LoRA checkpoint"""
+
+        lora_path = Path(lora_path)
+        assert lora_path.is_file(), f"{lora_path} does not exist or is not a file"
+
+        state_dict = safetensors.torch.load_file(lora_path)
+
+        self._load_lora_state_dict(state_dict, scaling=scaling)
+
+    def _load_lora_state_dict(
+        self, lora_state_dict: Dict[str, torch.Tensor], scaling: float = 2.0
+    ):
+        """Loads LoRA state_dict"""
+
+        lora_dtypes = set([p.dtype for p in lora_state_dict.values()])
+        assert (
+            len(lora_dtypes) == 1
+        ), f"LoRA weights have multipe different dtypes {lora_dtypes}. All weights need to have the same dtype"
+        lora_dtype = lora_dtypes.pop()
+        assert (
+            lora_dtype == self.dtype
+        ), f"LoRA weights dtype differs from model's dtype {lora_dtype} != {self.dtype}"
+        assert all("lora" in key for key in lora_state_dict.keys())
+
+        # move tensors to device
+        lora_state_dict = {k: v.to(self.device) for k, v in lora_state_dict.items()}
+
+        state_dict = self.state_dict()
+
+        if self.args.lora is None:
+            logging.info("Loading and merging LoRA weights...")
+
+            # replace every nn.Linear with a LoRALinear with 'meta' device except the output layer
+            named_modules = dict(self.named_modules())
+            for name, module in named_modules.items():
+                if isinstance(module, nn.Linear) and name != "output":
+                    layer_id = name.split(".")[1]
+                    if layer_id not in self.layers:
+                        logging.debug(
+                            "Skipping parameter %s at pipeline rank %d",
+                            name,
+                            self.pipeline_rank,
+                        )
+                    else:
+                        weight = (
+                            module.weight
+                            + (
+                                lora_state_dict[name + ".lora_B.weight"]
+                                @ lora_state_dict[name + ".lora_A.weight"]
+                            )
+                            * scaling
+                        )
+
+                        state_dict[name + ".weight"] = weight
+        else:
+            logging.info("Loading LoRA weights...")
+            for k, v in lora_state_dict.items():
+                state_dict.update(lora_state_dict)
+
+                layer_id = k.split(".")[1]
+                if layer_id in self.layers:
+                    state_dict[k] = v
+                else:
+                    logging.debug(
+                        "Skipping parameter %s at pipeline rank %d",
+                        k,
+                        self.pipeline_rank,
+                    )
+
+        self.load_state_dict(state_dict, strict=True)

src/mistral_inference/main.py

@@ -1,7 +1,7 @@
 import logging
 import os
 from pathlib import Path
-from typing import List
+from typing import List, Optional
 
 import fire  # type: ignore
 import torch
@@ -46,6 +46,7 @@ def interactive(
     temperature: float = 0.7,
     num_pipeline_ranks: int = 1,
     instruct: bool = False,
+    lora_path: Optional[str] = None,
 ) -> None:
     if is_torchrun():
         torch.distributed.init_process_group()
@@ -64,6 +65,10 @@ def interactive(
         Path(model_path), max_batch_size=3, num_pipeline_ranks=num_pipeline_ranks
     )
 
+    # load LoRA
+    if lora_path is not None:
+        transformer.load_lora(Path(lora_path))
+
     prompt: str = ""
     messages: List[UserMessage | AssistantMessage] = []
 
@@ -117,6 +122,7 @@ def demo(
     model_path: str,
     max_tokens: int = 35,
     temperature: float = 0,
+    lora_path: Optional[str] = None,
 ) -> None:
     if is_torchrun():
         torch.distributed.init_process_group()
@@ -131,6 +137,10 @@ def demo(
     transformer = Transformer.from_folder(
         Path(model_path), max_batch_size=3, num_pipeline_ranks=num_pipeline_ranks
     )
+    # load LoRA
+    if lora_path is not None:
+        transformer.load_lora(Path(lora_path))
+
     mistral_tokenizer: MistralTokenizer = load_tokenizer(Path(model_path))
     tokenizer: Tokenizer = mistral_tokenizer.instruct_tokenizer.tokenizer
 

src/mistral_inference/model.py

@@ -2,6 +2,7 @@
 import logging
 import math
 from dataclasses import dataclass
+from functools import partial
 from pathlib import Path
 from typing import Any, List, Mapping, Optional, Tuple, Union
 
@@ -16,6 +17,7 @@
     CacheInputMetadata,
     CacheView,
 )
+from mistral_inference.lora import LoraArgs, LoRALinear, LoRALoaderMixin
 from mistral_inference.moe import MoeArgs, MoeLayer
 from mistral_inference.rope import apply_rotary_emb, precompute_freqs_cis
 
@@ -37,6 +39,8 @@ class ModelArgs(Serializable):
     rope_theta: Optional[float] = None
     # If this is set, we will use MoE layers instead of dense layers.
     moe: Optional[MoeArgs] = None
+    # If this is set, we will load LoRA linear layers instead of linear layers.
+    lora: Optional[LoraArgs] = None
 
 
 @dataclass
@@ -61,6 +65,13 @@ def repeat_kv(
     return keys, values
 
 
+def maybe_lora(args: ModelArgs) -> Union[nn.Linear, LoRALinear]:
+    if args.lora is None:
+        return nn.Linear
+    else:
+        return partial(LoRALinear, rank=args.lora.rank, scaling=args.lora.scaling)
+
+
 class Attention(nn.Module):
     def __init__(self, args: ModelArgs):
         super().__init__()
@@ -74,10 +85,11 @@ def __init__(self, args: ModelArgs):
 
         self.scale = self.args.head_dim**-0.5
 
-        self.wq = nn.Linear(args.dim, args.n_heads * args.head_dim, bias=False)
-        self.wk = nn.Linear(args.dim, args.n_kv_heads * args.head_dim, bias=False)
-        self.wv = nn.Linear(args.dim, args.n_kv_heads * args.head_dim, bias=False)
-        self.wo = nn.Linear(args.n_heads * args.head_dim, args.dim, bias=False)
+        MaybeLora = maybe_lora(args)
+        self.wq = MaybeLora(args.dim, args.n_heads * args.head_dim, bias=False)
+        self.wk = MaybeLora(args.dim, args.n_kv_heads * args.head_dim, bias=False)
+        self.wv = MaybeLora(args.dim, args.n_kv_heads * args.head_dim, bias=False)
+        self.wo = MaybeLora(args.n_heads * args.head_dim, args.dim, bias=False)
 
     def forward(
         self,
@@ -127,9 +139,10 @@ class FeedForward(nn.Module):
     def __init__(self, args: ModelArgs):
         super().__init__()
 
-        self.w1 = nn.Linear(args.dim, args.hidden_dim, bias=False)
-        self.w2 = nn.Linear(args.hidden_dim, args.dim, bias=False)
-        self.w3 = nn.Linear(args.dim, args.hidden_dim, bias=False)
+        MaybeLora = maybe_lora(args)
+        self.w1 = MaybeLora(args.dim, args.hidden_dim, bias=False)
+        self.w2 = MaybeLora(args.hidden_dim, args.dim, bias=False)
+        self.w3 = MaybeLora(args.dim, args.hidden_dim, bias=False)
 
     def forward(self, x: torch.Tensor) -> torch.Tensor:
         return self.w2(nn.functional.silu(self.w1(x)) * self.w3(x))  # type: ignore
@@ -179,7 +192,7 @@ def forward(
         return out
 
 
-class Transformer(nn.Module):
+class Transformer(nn.Module, LoRALoaderMixin):
     def __init__(
         self,
         args: ModelArgs,