--- a +++ b/generate/base.py @@ -0,0 +1,221 @@ +## This file is adapted from the original file from the Lightning-AI lit-gpt repository: https://github.com/Lightning-AI/lit-gpt + +import sys +import time +from pathlib import Path +from typing import Any, Literal, Optional + +import lightning as L +import torch +import torch._dynamo.config +import torch._inductor.config +from lightning.fabric.plugins import BitsandbytesPrecision +from lightning.fabric.strategies import FSDPStrategy + +# support running without installing as a package +wd = Path(__file__).parent.parent.resolve() +sys.path.append(str(wd)) + +from lit_gpt import GPT, Config, Tokenizer +from lit_gpt.model import Block +from lit_gpt.utils import ( + check_valid_checkpoint_dir, + get_default_supported_precision, + gptq_quantization, + load_checkpoint, +) + + +def multinomial_num_samples_1(probs: torch.Tensor) -> torch.Tensor: + if torch._dynamo.is_compiling(): + # Faster alternative to `torch.multinomial(probs, num_samples=1)` that is also CUDAGraph friendly + distribution = torch.empty_like(probs).exponential_(1) + return torch.argmax(probs / distribution, dim=-1, keepdim=True) + return torch.multinomial(probs, num_samples=1) + + +def sample(logits: torch.Tensor, temperature: float = 1.0, top_k: Optional[int] = None) -> torch.Tensor: + logits = logits[0, -1] + # optionally crop the logits to only the top k options + if top_k is not None: + v, i = torch.topk(logits, min(top_k, logits.size(-1))) + # do not use `torch.where` as in nanogpt because it will repeat top-k collisions + logits = torch.full_like(logits, float("-inf")).scatter_(-1, i, v) + # optionally scale the logits and sample from a probability distribution + if temperature > 0.0: + probs = torch.nn.functional.softmax(logits / temperature, dim=-1) + return multinomial_num_samples_1(probs) + return torch.argmax(logits, dim=-1, keepdim=True) + + +def next_token(model: GPT, input_pos: torch.Tensor, x: torch.Tensor, **kwargs: Any) -> torch.Tensor: + logits = model(x, input_pos) + next = sample(logits, **kwargs) + return next.type_as(x) + + +@torch.inference_mode() +def generate( + model: GPT, + prompt: torch.Tensor, + max_returned_tokens: int, + *, + temperature: float = 1.0, + top_k: Optional[int] = None, + eos_id: Optional[int] = None, +) -> torch.Tensor: + """Takes a conditioning sequence (prompt) as input and continues to generate as many tokens as requested. + + The implementation of this function is modified from A. Karpathy's nanoGPT. + + Args: + model: The model to use. + prompt: Tensor of shape (T) with indices of the prompt sequence. + max_returned_tokens: The maximum number of tokens to return (given plus generated). + temperature: Scales the predicted logits by 1 / temperature. + top_k: If specified, only sample among the tokens with the k highest probabilities. + eos_id: If specified, stop generating any more token once the <eos> token is triggered. + """ + T = prompt.size(0) + assert max_returned_tokens > T + if model.max_seq_length < max_returned_tokens - 1: + # rolling the kv cache based on the `input_pos` value would be necessary. However, doing so would introduce a + # data dependency on the `input_pos` tensor and impact model compilation. Since this setting is uncommon, we do + # not support it to avoid negatively impacting the overall speed + raise NotImplementedError(f"max_seq_length {model.max_seq_length} needs to be >= {max_returned_tokens - 1}") + + device = prompt.device + tokens = [prompt] + input_pos = torch.tensor([T], device=device) + token = next_token( + model, torch.arange(0, T, device=device), prompt.view(1, -1), temperature=temperature, top_k=top_k + ).clone() + tokens.append(token) + for _ in range(2, max_returned_tokens - T + 1): + token = next_token(model, input_pos, token.view(1, -1), temperature=temperature, top_k=top_k).clone() + tokens.append(token) + if token == eos_id: + break + input_pos = input_pos.add_(1) + return torch.cat(tokens) + + +def main( + prompt: str = "What food do llamas eat?", + *, + num_samples: int = 1, + max_new_tokens: int = 50, + top_k: Optional[int] = 200, + temperature: float = 0.8, + checkpoint_dir: Path = Path("checkpoints/stabilityai/stablelm-base-alpha-3b"), + quantize: Optional[Literal["bnb.nf4", "bnb.nf4-dq", "bnb.fp4", "bnb.fp4-dq", "bnb.int8", "gptq.int4"]] = None, + strategy: str = "auto", + devices: int = 1, + precision: Optional[str] = None, + compile: bool = False, +) -> None: + """Generates text samples based on a pre-trained model and tokenizer. + + Args: + prompt: The prompt string to use for generating the samples. + num_samples: The number of text samples to generate. + max_new_tokens: The number of generation steps to take. + top_k: The number of top most probable tokens to consider in the sampling process. + temperature: A value controlling the randomness of the sampling process. Higher values result in more random + samples. + checkpoint_dir: The checkpoint directory to load. + quantize: Whether to quantize the model and using which method: + - bnb.nf4, bnb.nf4-dq, bnb.fp4, bnb.fp4-dq: 4-bit quantization from bitsandbytes + - bnb.int8: 8-bit quantization from bitsandbytes + - gptq.int4: 4-bit quantization from GPTQ + for more details, see https://github.com/Lightning-AI/lit-gpt/blob/main/tutorials/quantize.md + strategy: Indicates the Fabric strategy setting to use. + devices: How many devices to use. + precision: Indicates the Fabric precision setting to use. + compile: Whether to compile the model. + """ + precision = precision or get_default_supported_precision(training=False) + + plugins = None + if quantize is not None: + if devices > 1: + raise NotImplementedError( + "Quantization is currently not supported for multi-GPU training. Please set devices=1 when using the" + " --quantize flag." + ) + if quantize.startswith("bnb."): + if "mixed" in precision: + raise ValueError("Quantization and mixed precision is not supported.") + dtype = {"16-true": torch.float16, "bf16-true": torch.bfloat16, "32-true": torch.float32}[precision] + plugins = BitsandbytesPrecision(quantize[4:], dtype) + precision = None + + if strategy == "fsdp": + strategy = FSDPStrategy(auto_wrap_policy={Block}, cpu_offload=False) + + fabric = L.Fabric(devices=devices, precision=precision, strategy=strategy, plugins=plugins) + fabric.launch() + + check_valid_checkpoint_dir(checkpoint_dir) + + config = Config.from_json(checkpoint_dir / "lit_config.json") + + if quantize == "gptq.int4": + model_file = "lit_model_gptq.4bit.pth" + if not (checkpoint_dir / model_file).is_file(): + raise ValueError("Please run `python quantize/gptq.py` first") + else: + model_file = "lit_model.pth" + checkpoint_path = checkpoint_dir / model_file + + tokenizer = Tokenizer(checkpoint_dir) + encoded = tokenizer.encode(prompt, device=fabric.device) + prompt_length = encoded.size(0) + max_returned_tokens = prompt_length + max_new_tokens + + fabric.print(f"Loading model {str(checkpoint_path)!r} with {config.__dict__}", file=sys.stderr) + t0 = time.perf_counter() + with fabric.init_module(empty_init=True), gptq_quantization(quantize == "gptq.int4"): + model = GPT(config) + fabric.print(f"Time to instantiate model: {time.perf_counter() - t0:.02f} seconds.", file=sys.stderr) + with fabric.init_tensor(): + # set the max_seq_length to limit the memory usage to what we need + model.max_seq_length = max_returned_tokens + # enable the kv cache + model.set_kv_cache(batch_size=1) + model.eval() + + if compile: + torch._dynamo.config.automatic_dynamic_shapes = True + torch._inductor.config.triton.unique_kernel_names = True + torch._inductor.config.coordinate_descent_tuning = True + global next_token + next_token = torch.compile(next_token, mode="reduce-overhead") + + model = fabric.setup_module(model) + + t0 = time.perf_counter() + load_checkpoint(fabric, model, checkpoint_path) + fabric.print(f"Time to load the model weights: {time.perf_counter() - t0:.02f} seconds.", file=sys.stderr) + + L.seed_everything(1234) + for i in range(num_samples): + t0 = time.perf_counter() + y = generate(model, encoded, max_returned_tokens, temperature=temperature, top_k=top_k) + t = time.perf_counter() - t0 + for block in model.transformer.h: + block.attn.kv_cache.reset_parameters() + fabric.print(tokenizer.decode(y)) + tokens_generated = y.size(0) - prompt_length + fabric.print( + f"Time for inference {i + 1}: {t:.02f} sec total, {tokens_generated / t:.02f} tokens/sec", file=sys.stderr + ) + if fabric.device.type == "cuda": + fabric.print(f"Memory used: {torch.cuda.max_memory_allocated() / 1e9:.02f} GB", file=sys.stderr) + + +if __name__ == "__main__": + from jsonargparse import CLI + + torch.set_float32_matmul_precision("high") + CLI(main)