Transformers

transformer是一个提供了所有你需要做预训练的模型推理或者训练的库。主要功能包括：

Inference

pipeline

from transformers import pipeline

pipeline = pipeline(task="text-generation", model="google/gemma-2-2b")
pipeline("the secret to baking a really good cake is ")
[{'generated_text': 'the secret to baking a really good cake is 1. the right ingredients 2. the'}]

text generation

from transformers import AutoModelForSeq2SeqLM, AutoTokenizer, GenerationConfig

tokenizer = AutoTokenizer.from_pretrained("google-t5/t5-small")
model = AutoModelForSeq2SeqLM.from_pretrained("google-t5/t5-small")

translation_generation_config = GenerationConfig(
    num_beams=4,
    early_stopping=True,
    decoder_start_token_id=0,
    eos_token_id=model.config.eos_token_id,
    pad_token=model.config.pad_token_id,
)

translation_generation_config.save_pretrained("/tmp", config_file_name="translation_generation_config.json", push_to_hub=True)

generation_config = GenerationConfig.from_pretrained("/tmp", config_file_name="translation_generation_config.json")
inputs = tokenizer("translate English to French: Configuration files are easy to use!", return_tensors="pt")
outputs = model.generate(**inputs, generation_config=generation_config)
print(tokenizer.batch_decode(outputs, skip_special_tokens=True))

cache

Cache Type	Memory Efficient	Supports torch.compile()	Initialization Recommended	Latency	Long Context Generation
Dynamic Cache	No	No	No	Mid	No
Static Cache	No	Yes	Yes	High	No
Offloaded Cache	Yes	No	No	Low	Yes
Offloaded Static Cache	No	Yes	Yes	High	Yes
Quantized Cache	Yes	No	No	Low	Yes
Sliding Window Cache	No	Yes	Yes	High	No

import torch
from transformers import AutoTokenizer, AutoModelForCausalLM, DynamicCache

tokenizer = AutoTokenizer.from_pretrained("meta-llama/Llama-2-7b-chat-hf")
model = AutoModelForCausalLM.from_pretrained("meta-llama/Llama-2-7b-chat-hf", torch_dtype=torch.float16).to("cuda:0")
inputs = tokenizer("I like rock music because", return_tensors="pt").to(model.device)

past_key_values = DynamicCache()
out = model.generate(**inputs, do_sample=False, max_new_tokens=20, past_key_values=past_key_values)

Training

Trainer

Trainer 包含了模型训练的所有步骤.

1. 计算一个训练步的损失
2. 反向传递计算梯度
3. 根据梯度更新参数
4. 直到达到训练epoch数。

from transformers import Trainer

trainer = Trainer(
    model=model,
    args=training_args,
    train_dataset=dataset["train"],
    eval_dataset=dataset["test"],
    processing_class=tokenizer,
    data_collator=data_collator,
    compute_metrics=compute_metrics,
)

trainer.train()

Accelerate

加几行代码到Pytorch代码就可以实现模型并行加速

+ from accelerate import Accelerator
+ accelerator = Accelerator()

+ model, optimizer, training_dataloader, scheduler = accelerator.prepare(
+     model, optimizer, training_dataloader, scheduler
+ )

  for batch in training_dataloader:
      optimizer.zero_grad()
      inputs, targets = batch
      inputs = inputs.to(device)
      targets = targets.to(device)
      outputs = model(inputs)
      loss = loss_function(outputs, targets)
+     accelerator.backward(loss)
      optimizer.step()
      scheduler.step()

DistributedDataParallel

compute_environment: LOCAL_MACHINE
distributed_type: MULTI_GPU
downcast_bf16: 'no'
gpu_ids: all
machine_rank: 0 #change rank as per the node
main_process_ip: 192.168.20.1
main_process_port: 9898
main_training_function: main
mixed_precision: fp16
num_machines: 2
num_processes: 8
rdzv_backend: static
same_network: true
tpu_env: []
tpu_use_cluster: false
tpu_use_sudo: false
use_cpu: false

FullyShardedDataParallel

compute_environment: LOCAL_MACHINE
distributed_type: FSDP
downcast_bf16: 'no'
fsdp_config:
  fsdp_auto_wrap_policy: TRANSFORMER_BASED_WRAP
  fsdp_backward_prefetch_policy: BACKWARD_PRE
  fsdp_forward_prefetch: true
  fsdp_offload_params: false
  fsdp_sharding_strategy: 1
  fsdp_state_dict_type: FULL_STATE_DICT
  fsdp_sync_module_states: true
  fsdp_transformer_layer_cls_to_wrap: BertLayer
  fsdp_use_orig_params: true
machine_rank: 0
main_training_function: main
mixed_precision: bf16
num_machines: 1
num_processes: 2
rdzv_backend: static
same_network: true
tpu_env: []
tpu_use_cluster: false
tpu_use_sudo: false
use_cpu: false

运行

accelerate launch \
    ./examples/pytorch/text-classification/run_glue.py \
    --model_name_or_path google-bert/bert-base-cased \
    --task_name $TASK_NAME \
    --do_train \
    --do_eval \
    --max_seq_length 128 \
    --per_device_train_batch_size 16 \
    --learning_rate 5e-5 \
    --num_train_epochs 3 \
    --output_dir /tmp/$TASK_NAME/ \
    --overwrite_output_dir

PEFT

from peft import LoraConfig, TaskType, get_peft_model
from transformers import AutoModelForCausalLM

# create LoRA configuration object
lora_config = LoraConfig(
    task_type=TaskType.CAUSAL_LM, # type of task to train on
    inference_mode=False, # set to False for training
    r=8, # dimension of the smaller matrices
    lora_alpha=32, # scaling factor
    lora_dropout=0.1 # dropout of LoRA layers
)

model.add_adapter(lora_config, adapter_name="lora_1")
trainer = Trainer(model=model, ...)
trainer.train()

quantization

import torch
from transformers import AutoModelForCausalLM, BitsAndBytesConfig

quantization_config = BitsAndBytesConfig(load_in_8bit=True)

model_8bit = AutoModelForCausalLM.from_pretrained(
    "facebook/opt-350m", 
    device_map="auto",
    quantization_config=quantization_config, 
    torch_dtype="auto"
)
model_8bit.model.decoder.layers[-1].final_layer_norm.weight.dtype