Can I pretrain LLaMA from scratch?

Beginners
1

Hi. I want to train LLaMA from scratch.
I don’t want to finetune it, but I wanna try pretrain it from scratch and see how it goes.
How could I do it?

Thanks

2

Generally, you initialize the model with random weights as shown here and then train the model like any other.

Except you can’t. To understand why, please check Table 1 and Table 15 in the LLaMa paper. However, I’d really like to hear back from you if you actually can train LLaMa from scratch. :metal:

1 Like
3

Thanks a lot
I just wanted to know how to pre-train LLaMA, and try it for fun.
I did not intended to actually use the custom pre-trained model. :grinning:

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4

Updated link to the LLaMA paper: https://arxiv.org/pdf/2302.13971.pdf

5

I am also interested in initializing empty Llama, just for the sake of faster development time, instead of loading full llama each time

6

I have a small ‘Llama’ model (~1M parameters) by changing the config and trying to train it with my data. However, the model performs terribly on a small dataset(cannot overfit), and I don’t know why. Here is the link to my problem: Failed to train Llama model
If possible, can I have a small demo code on how to train it?

7

For those who want to build Llama from scratch, this article might be quite useful.

2 Likes
8

I tried just reinitializing the layers directly but it didn’t work:

import torch
from transformers import AutoModelForCausalLM, AutoConfig 
import torch.nn as nn

def main_reinit_model():
    """
    ref: https://stackoverflow.com/questions/76971761/how-to-adapt-llama-v2-model-to-less-than-7b-parameters
    ref: https://github.com/huggingface/transformers/blob/main/src/transformers/models/llama/modeling_llama.py#L721
    ref: https://chat.openai.com/c/977d0cb0-b819-48ac-be5c-6e482ad5e518 
    """
    print('Starting to reinitialize the model...')
    # Load the pretrained LLaMA v2 config
    config = AutoConfig.from_pretrained("meta-llama/Llama-2-7b-hf")
    # print(f'config: {config} {type(config)}')
    # Print the original number of parameters 
    model = AutoModelForCausalLM.from_config(config) 
    # put model on device cuda
    model = model.to('cuda')
    # print the model's device
    print(f'{model.device=}')
    # print(f'{model=}')
    # print("Original number of parameters:", sum(p.numel() for p in model.parameters()))
    # go through all parameters and compute the l1 norm and sum it then print it
    norm_model = sum(p.norm(1) for p in model.parameters())
    # loop through modules of model and reinitialize weights with normal_mean, 0.02 
    print(f'{norm_model=}')
    """
    go through model and print all laters
    """
    # model.init_weights()  # didn't work
    # model._init_weights(module)  # didn't work needs module
    # for name, param in model.named_parameters():
    #     model._init_weights(param)
    # model.post_init()
    reinitialize_weights(model)
    # model._initialize_weights(module)  # didn't work needs module
    # for name, param in model.named_parameters():
    #     print(f'{name=} {param.shape=}')
    norm_model = sum(p.norm(1) for p in model.parameters())
    print(f'{norm_model=}')

def reinitialize_weights(model) -> None:
    for module in model.modules():
        if isinstance(module, nn.Linear):
            nn.init.normal_(module.weight, mean=0, std=0.02)
            if module.bias is not None:
                nn.init.constant_(module.bias, 0)

def _init_weights(self, module):
    std = self.config.initializer_range
    if isinstance(module, nn.Linear):
        module.weight.data.normal_(mean=100.0, std=std)
        if module.bias is not None:
            module.bias.data.zero_()
    elif isinstance(module, nn.Embedding):
        module.weight.data.normal_(mean=0.0, std=std)
        if module.padding_idx is not None:
            module.weight.data[module.padding_idx].zero_()

def main_generate_smaller_model():
    """
    ref: https://stackoverflow.com/questions/76971761/how-to-adapt-llama-v2-model-to-less-than-7b-parameters
    """
    print('Starting to reinitialize the model...')
    # Load the pretrained LLaMA v2 config
    config = AutoConfig.from_pretrained("meta-llama/Llama-2-7b-hf")
    print(f'config: {config} {type(config)}')
    # Print the original number of parameters 
    model = AutoModelForCausalLM.from_config(config) 
    print("Original number of parameters:", sum(p.numel() for p in model.parameters()))

    # Modify the config to reduce size
    config.hidden_size = 2048
    config.num_hidden_layers = 12

    # Create new smaller model from modified config
    smaller_model = AutoModelForCausalLM.from_config(config)
    print("New number of parameters:", sum(p.numel() for p in smaller_model.parameters()))

if __name__ == '__main__':
    import time
    start = time.time()
    # main_generate_smaller_model() 
    main_reinit_model()
    print('Done!\a\a\a')

anyone know why it fails?

ref: machine learning - How does one reinitialize the weights of a Hugging Face LLaMA v2 model the official way as the original model? - Stack Overflow
ref: How does one reinitialize the weights of a Hugging Face LLaMA v2 model the official way as the original model?

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