我用numpy实现了GPT-2，GPT-2源码，GPT-2模型加速推理，并且可以在树莓派上运行，读了不少hungging face源码，手动实现了numpy的GPT2模型

之前分别用numpy实现了mlp，cnn，lstm和bert模型，这周顺带搞一下GPT-2，纯numpy实现，最重要的是可在树莓派上或其他不能安装pytorch的板子上运行，生成数据

gpt-2的mask-multi-headed-self-attention我现在才彻底的明白它是真的牛逼，比bert的multi-headed-self-attention牛的不是一点半点，提出mask的人智商也是相当高了

这次模型依然是从hungging face上找的一个，gpt-2 small版本，参数比bert还小，主要是gpt-2没有token-type那个2*768的矩阵和一个pooler矩阵，别的都有

gpt-2的模型结构和bert类似，只不过multi-headed-self-attention换成了mask-multi-headed-self-attention，另外

layer_normalization层放到了attention层之前和feedforword层之前

 

最重点的是，我的代码实现了gpt-2推理加速，以前的gpt-2的工程里经常是生成一个新的token后和原来的token序列拼接起来，再给模型输入，这会使模型大大增加计算量，同时mask失去了它的意义，每次都会把之前的token重新推理一边，浪费时间，我的代码中已经实现使用生成的token作为模型输入去推理后面的结果，计算量大大减少，速度大大提升，试想一下向量做矩阵乘法和矩阵做矩阵乘法的差异，同样生成100个token，在cpu上的加速效果快了一倍，如果token长度更长，则加速效果会更明显

 

上numpy代码

import numpy as np
import time

def top_k_sampling(probs, k):
    # 使用argsort对概率分布数组进行排序，得到索引数组
    sorted_indices = np.argsort(probs)[::-1]
    # 选择前K个概率最高的词的索引
    topk_indices = sorted_indices[:k]
    # 根据选择的Top-K索引进行进一步处理，例如按概率重新归一化或随机采样
    return topk_indices

def random_sampling(array, k):
    sample = np.random.choice(array, size=k, replace=False)
    return sample

def word_embedding(input_ids, word_embeddings):
    return word_embeddings[input_ids]

def position_embedding(position_ids, position_embeddings):
    return position_embeddings[position_ids]

def token_type_embedding(token_type_ids, token_type_embeddings):
    return token_type_embeddings[token_type_ids]

def softmax(x, axis=None):
    # e_x = np.exp(x).astype(np.float32) #
    e_x = np.exp(x - np.max(x, axis=axis, keepdims=True))
    sum_ex = np.sum(e_x, axis=axis,keepdims=True).astype(np.float32)
    return e_x / sum_ex

def scaled_dot_product_attention(Q, K, V, mask=None):

    d_k = Q.shape[-1]
    attention_scores = np.matmul(Q, K.transpose(0, 2, 1)) / np.sqrt(d_k)   #一致
    if mask is not None:
        # min_value = scores.min()
        min_value = np.finfo(attention_scores.dtype).min      #找的scores.dtype 这个类型数据的最小值
        # scores = np.where(mask, scores, np.full_like(scores, -np.inf))
        scores = np.where(mask, attention_scores, np.full_like(attention_scores, min_value))    # 用最小值替换0的部分

    attention_weights = softmax(scores, axis=-1)      # 这样softmax的权重在本来是0的地方得到的数值是0

    output = np.matmul(attention_weights, V)        #一致了
    return output, attention_weights

def scaled_dot_product_attention2(Q, K, V):     # 单部推理 降低计算量

    global att_scores
    d_k = Q.shape[-1]
    attention_scores = np.matmul(Q, K.transpose(0, 2, 1)) / np.sqrt(d_k)   #一致
    attention_weights = softmax(attention_scores, axis=-1)      # 这样softmax的权重在本来是0的地方得到的数值是0
    output = np.matmul(attention_weights, V)        #一致了
    return output, attention_weights

global_q = {}
global_k = {}
global_v = {}
def mask_multihead_attention(i,input, num_heads,W_Q,B_Q,W_K,B_K,W_V,B_V,W_O,B_O):

    global global_q,global_k,global_v
    q = np.matmul(input, W_Q)+B_Q
    k = np.matmul(input, W_K)+B_K
    v = np.matmul(input, W_V)+B_V    

    if q.shape[-2] == 1:
        k = global_k[i] = np.concatenate([global_k[i],k],axis=-2)
        v = global_v[i] = np.concatenate([global_v[i],v],axis=-2)
    else:
        global_q[i] = q
        global_k[i] = k
        global_v[i] = v

    _,n,_ = k.shape
    # 分割输入为多个头
    q = np.split(q, num_heads, axis=-1)
    k = np.split(k, num_heads, axis=-1)
    v = np.split(v, num_heads, axis=-1)   #到这里都是一致的

    outputs = []
    if q[0].shape[-2] != 1:
        mask = np.tril(np.ones((n, n)))   #下三角矩阵
        for q_,k_,v_ in zip(q,k,v):
            output, attention_weights = scaled_dot_product_attention(q_, k_, v_,mask)    #一致
            outputs.append(output)
    else:
        for q_,k_,v_ in zip(q,k,v):
            output, attention_weights = scaled_dot_product_attention2(q_, k_, v_)    #一致
            outputs.append(output)

    outputs = np.concatenate(outputs, axis=-1)
    outputs = np.matmul(outputs, W_O)+B_O
    return outputs      #一致

def layer_normalization(x, weight, bias, eps=1e-12):
    mean = np.mean(x, axis=-1, keepdims=True)
    variance = np.var(x, axis=-1, keepdims=True)
    std = np.sqrt(variance + eps)
    normalized_x = (x - mean) / std
    output = weight * normalized_x + bias
    return output

def feed_forward_layer(inputs, weight, bias=None, activation='relu'):
    if bias is not None:
        linear_output = np.matmul(inputs,weight) + bias
    else:
        linear_output = np.matmul(inputs,weight)

    if activation == 'relu':
        activated_output = np.maximum(0, linear_output)  # ReLU激活函数
    elif activation == 'gelu':
        activated_output = 0.5 * linear_output * (1 + np.tanh(np.sqrt(2 / np.pi) * (linear_output + 0.044715 * np.power(linear_output, 3))))  # GELU激活函数

    elif activation == "tanh" :
        activated_output = np.tanh(linear_output)
    else:
        activated_output = linear_output  # 无激活函数

    return activated_output

def residual_connection(inputs, residual):
    # 残差连接
    residual_output = inputs + residual
    return residual_output

with open('vocab.txt', 'r', encoding='utf-8') as f:
    vocab = f.readlines()
    vocab = [i.strip() for i in vocab]
    # print(len(vocab))

def tokenize_sentence(sentence):
    tokenized_sentence = list(sentence) # 在句子开头添加[cls]
    token_ids = [vocab.index(token) for token in tokenized_sentence]

    return token_ids

# 加载保存的模型数据
model_data = np.load('gpt2_model_params.npz')
# for i in model_data:
#     # print(i)
#     print(i,model_data[i].shape)

def get_sentence_ids(sentence):
    token_ids = tokenize_sentence(sentence)
    input_ids = np.array(token_ids)  # 输入的词汇id
    return input_ids

word_embeddings = model_data["transformer.wte.weight"]
position_embeddings = model_data["transformer.wpe.weight"]
def model_input(input_ids,position_ids):

    word_embedded = word_embedding(input_ids, word_embeddings)

    position_ids = np.array(position_ids)  # 位置id
    # 位置嵌入矩阵，形状为 (max_position, embedding_size)
    position_embedded = position_embedding(position_ids, position_embeddings)

    embedding_output = np.expand_dims(word_embedded + position_embedded, axis=0)
    return embedding_output

def gpt2(input,num_heads):

    for i in range(12):

        LayerNorm1_weight = model_data['transformer.h.{}.ln_1.weight'.format(i)]
        LayerNorm1_bias = model_data['transformer.h.{}.ln_1.bias'.format(i)]
        # 调用多头自注意力函数
        W_QKV = model_data['transformer.h.{}.attn.c_attn.weight'.format(i)]
        B_QKV = model_data['transformer.h.{}.attn.c_attn.bias'.format(i)]
        W_O = model_data['transformer.h.{}.attn.c_proj.weight'.format(i)]
        B_O = model_data['transformer.h.{}.attn.c_proj.bias'.format(i)]

        LayerNorm2_weight = model_data['transformer.h.{}.ln_2.weight'.format(i)]
        LayerNorm2_bias = model_data['transformer.h.{}.ln_2.bias'.format(i)]

        intermediate_weight = model_data['transformer.h.{}.mlp.c_fc.weight'.format(i)]
        intermediate_bias = model_data['transformer.h.{}.mlp.c_fc.bias'.format(i)]
        dense_weight = model_data['transformer.h.{}.mlp.c_proj.weight'.format(i)]
        dense_bias = model_data['transformer.h.{}.mlp.c_proj.bias'.format(i)]

        input1 = layer_normalization(input,LayerNorm1_weight,LayerNorm1_bias)     #这里和模型输出一致
        W_Q,W_K,W_V = np.split(W_QKV, 3, axis=-1)
        B_Q,B_K,B_V = np.split(B_QKV, 3, axis=-1)
        output = mask_multihead_attention(i,input1, num_heads,W_Q,B_Q,W_K,B_K,W_V,B_V,W_O,B_O)     #一致
        output1 = residual_connection(input,output)      #一致

        output = layer_normalization(output1,LayerNorm2_weight,LayerNorm2_bias)    #一致
        output = feed_forward_layer(output, intermediate_weight, intermediate_bias, activation='gelu')
        output = feed_forward_layer(output, dense_weight, dense_bias, activation='')       #一致
        output2 = residual_connection(output1,output)

        input = output2

    ln_f_weight = model_data['transformer.ln_f.weight']
    ln_f_bias = model_data['transformer.ln_f.bias']
    output = layer_normalization(output2,ln_f_weight,ln_f_bias)

    return output

classifier_weight = model_data['lm_head.weight']
def predict(sentence="今天是个好日子",accelerater=True,gen_len=100):

    start = time.time()
    sentence_ids = get_sentence_ids(sentence)
    position_ids = range(len(sentence_ids))
    print("prompt输入:",sentence)
    for i in range(gen_len):
        embeddings = model_input(sentence_ids,position_ids)
        output = gpt2(embeddings,num_heads=12)
        # print(output)
        output = feed_forward_layer(output[:,-1], classifier_weight.T, activation='')

        samples = top_k_sampling(output[0],k=1)

        label_id = random_sampling(samples,k=1)

        print(vocab[label_id[0]],end="")

        if accelerater:      #是否使用加速推理减少计算量
            sentence_ids = label_id                                             #每次使用上一步的q，和全量的key和v做计算，比使用所有历史时间部的q计算量小很多，所以可以加速
            position_ids = [position_ids[-1]+1]
        else:
            sentence_ids = np.concatenate([sentence_ids,label_id],axis=-1)      #慢推理，每次都需要从头计算，计算量会越来越大
            position_ids = range(len(sentence_ids))

    end = time.time()

    print("\nspend time:",end-start)

if __name__ == "__main__":

    accelerater = False
    sentence = "今天是个好日子"  #我们要做的就是把握住这个机会

    predict(sentence,accelerater)

    # embeddings = model_input(sentence_ids)
    # output = gpt2(embeddings,num_heads=12)
    # # print(output)
    # output = feed_forward_layer(output[:,:], classifier_weight.T, activation='')

    # samples = np.argmax(output,axis=-1)

    # for i in samples[0]:
    #     print(vocab[i],end="")

结果：同样的结果，序列长度越长，时间上的差异越明显，这才生成100tokens，就已经明显看出速度的差异了

使用加速：
prompt输入: 今天是个好日子
，我们要做的就是把握住这个机会，把握住这个机会，把握住了，我相信我们的投资将会创造奇迹，而且我相信我们的投资团队一定能够创造奇迹，我相信我们的投资团队一定能够创造奇迹，我相信我们的投资团队一定能够创造
spend time: 22.19951105117798

不使用加速：
prompt输入: 今天是个好日子
，我们要做的就是把握住这个机会，把握住这个机会，把握住了，我相信我们的投资将会创造奇迹，而且我相信我们的投资团队一定能够创造奇迹，我相信我们的投资团队一定能够创造奇迹，我相信我们的投资团队一定能够创造
spend time: 42.4955039024353

模型参数：

transformer.wte.weight (21128, 768)
transformer.wpe.weight (1024, 768)
transformer.h.0.ln_1.weight (768,)
transformer.h.0.ln_1.bias (768,)
transformer.h.0.attn.c_attn.weight (768, 2304)
transformer.h.0.attn.c_attn.bias (2304,)
transformer.h.0.attn.c_proj.weight (768, 768)
transformer.h.0.attn.c_proj.bias (768,)
transformer.h.0.ln_2.weight (768,)
transformer.h.0.ln_2.bias (768,)
transformer.h.0.mlp.c_fc.weight (768, 3072)
transformer.h.0.mlp.c_fc.bias (3072,)
transformer.h.0.mlp.c_proj.weight (3072, 768)
transformer.h.0.mlp.c_proj.bias (768,)
transformer.h.1.ln_1.weight (768,)
transformer.h.1.ln_1.bias (768,)
transformer.h.1.attn.c_attn.weight (768, 2304)
transformer.h.1.attn.c_attn.bias (2304,)
transformer.h.1.attn.c_proj.weight (768, 768)
transformer.h.1.attn.c_proj.bias (768,)
transformer.h.1.ln_2.weight (768,)
transformer.h.1.ln_2.bias (768,)
transformer.h.1.mlp.c_fc.weight (768, 3072)
transformer.h.1.mlp.c_fc.bias (3072,)
transformer.h.1.mlp.c_proj.weight (3072, 768)
transformer.h.1.mlp.c_proj.bias (768,)
transformer.h.2.ln_1.weight (768,)
transformer.h.2.ln_1.bias (768,)
transformer.h.2.attn.c_attn.weight (768, 2304)
transformer.h.2.attn.c_attn.bias (2304,)
transformer.h.2.attn.c_proj.weight (768, 768)
transformer.h.2.attn.c_proj.bias (768,)
transformer.h.2.ln_2.weight (768,)
transformer.h.2.ln_2.bias (768,)
transformer.h.2.mlp.c_fc.weight (768, 3072)
transformer.h.2.mlp.c_fc.bias (3072,)
transformer.h.2.mlp.c_proj.weight (3072, 768)
transformer.h.2.mlp.c_proj.bias (768,)
transformer.h.3.ln_1.weight (768,)
transformer.h.3.ln_1.bias (768,)
transformer.h.3.attn.c_attn.weight (768, 2304)
transformer.h.3.attn.c_attn.bias (2304,)
transformer.h.3.attn.c_proj.weight (768, 768)
transformer.h.3.attn.c_proj.bias (768,)
transformer.h.3.ln_2.weight (768,)
transformer.h.3.ln_2.bias (768,)
transformer.h.3.mlp.c_fc.weight (768, 3072)
transformer.h.3.mlp.c_fc.bias (3072,)
transformer.h.3.mlp.c_proj.weight (3072, 768)
transformer.h.3.mlp.c_proj.bias (768,)
transformer.h.4.ln_1.weight (768,)
transformer.h.4.ln_1.bias (768,)
transformer.h.4.attn.c_attn.weight (768, 2304)
transformer.h.4.attn.c_attn.bias (2304,)
transformer.h.4.attn.c_proj.weight (768, 768)
transformer.h.4.attn.c_proj.bias (768,)
transformer.h.4.ln_2.weight (768,)
transformer.h.4.ln_2.bias (768,)
transformer.h.4.mlp.c_fc.weight (768, 3072)
transformer.h.4.mlp.c_fc.bias (3072,)
transformer.h.4.mlp.c_proj.weight (3072, 768)
transformer.h.4.mlp.c_proj.bias (768,)
transformer.h.5.ln_1.weight (768,)
transformer.h.5.ln_1.bias (768,)
transformer.h.5.attn.c_attn.weight (768, 2304)
transformer.h.5.attn.c_attn.bias (2304,)
transformer.h.5.attn.c_proj.weight (768, 768)
transformer.h.5.attn.c_proj.bias (768,)
transformer.h.5.ln_2.weight (768,)
transformer.h.5.ln_2.bias (768,)
transformer.h.5.mlp.c_fc.weight (768, 3072)
transformer.h.5.mlp.c_fc.bias (3072,)
transformer.h.5.mlp.c_proj.weight (3072, 768)
transformer.h.5.mlp.c_proj.bias (768,)
transformer.h.6.ln_1.weight (768,)
transformer.h.6.ln_1.bias (768,)
transformer.h.6.attn.c_attn.weight (768, 2304)
transformer.h.6.attn.c_attn.bias (2304,)
transformer.h.6.attn.c_proj.weight (768, 768)
transformer.h.6.attn.c_proj.bias (768,)
transformer.h.6.ln_2.weight (768,)
transformer.h.6.ln_2.bias (768,)
transformer.h.6.mlp.c_fc.weight (768, 3072)
transformer.h.6.mlp.c_fc.bias (3072,)
transformer.h.6.mlp.c_proj.weight (3072, 768)
transformer.h.6.mlp.c_proj.bias (768,)
transformer.h.7.ln_1.weight (768,)
transformer.h.7.ln_1.bias (768,)
transformer.h.7.attn.c_attn.weight (768, 2304)
transformer.h.7.attn.c_attn.bias (2304,)
transformer.h.7.attn.c_proj.weight (768, 768)
transformer.h.7.attn.c_proj.bias (768,)
transformer.h.7.ln_2.weight (768,)
transformer.h.7.ln_2.bias (768,)
transformer.h.7.mlp.c_fc.weight (768, 3072)
transformer.h.7.mlp.c_fc.bias (3072,)
transformer.h.7.mlp.c_proj.weight (3072, 768)
transformer.h.7.mlp.c_proj.bias (768,)
transformer.h.8.ln_1.weight (768,)
transformer.h.8.ln_1.bias (768,)
transformer.h.8.attn.c_attn.weight (768, 2304)
transformer.h.8.attn.c_attn.bias (2304,)
transformer.h.8.attn.c_proj.weight (768, 768)
transformer.h.8.attn.c_proj.bias (768,)
transformer.h.8.ln_2.weight (768,)
transformer.h.8.ln_2.bias (768,)
transformer.h.8.mlp.c_fc.weight (768, 3072)
transformer.h.8.mlp.c_fc.bias (3072,)
transformer.h.8.mlp.c_proj.weight (3072, 768)
transformer.h.8.mlp.c_proj.bias (768,)
transformer.h.9.ln_1.weight (768,)
transformer.h.9.ln_1.bias (768,)
transformer.h.9.attn.c_attn.weight (768, 2304)
transformer.h.9.attn.c_attn.bias (2304,)
transformer.h.9.attn.c_proj.weight (768, 768)
transformer.h.9.attn.c_proj.bias (768,)
transformer.h.9.ln_2.weight (768,)
transformer.h.9.ln_2.bias (768,)
transformer.h.9.mlp.c_fc.weight (768, 3072)
transformer.h.9.mlp.c_fc.bias (3072,)
transformer.h.9.mlp.c_proj.weight (3072, 768)
transformer.h.9.mlp.c_proj.bias (768,)
transformer.h.10.ln_1.weight (768,)
transformer.h.10.ln_1.bias (768,)
transformer.h.10.attn.c_attn.weight (768, 2304)
transformer.h.10.attn.c_attn.bias (2304,)
transformer.h.10.attn.c_proj.weight (768, 768)
transformer.h.10.attn.c_proj.bias (768,)
transformer.h.10.ln_2.weight (768,)
transformer.h.10.ln_2.bias (768,)
transformer.h.10.mlp.c_fc.weight (768, 3072)
transformer.h.10.mlp.c_fc.bias (3072,)
transformer.h.10.mlp.c_proj.weight (3072, 768)
transformer.h.10.mlp.c_proj.bias (768,)
transformer.h.11.ln_1.weight (768,)
transformer.h.11.ln_1.bias (768,)
transformer.h.11.attn.c_attn.weight (768, 2304)
transformer.h.11.attn.c_attn.bias (2304,)
transformer.h.11.attn.c_proj.weight (768, 768)
transformer.h.11.attn.c_proj.bias (768,)
transformer.h.11.ln_2.weight (768,)
transformer.h.11.ln_2.bias (768,)
transformer.h.11.mlp.c_fc.weight (768, 3072)
transformer.h.11.mlp.c_fc.bias (3072,)
transformer.h.11.mlp.c_proj.weight (3072, 768)
transformer.h.11.mlp.c_proj.bias (768,)
transformer.ln_f.weight (768,)
transformer.ln_f.bias (768,)
lm_head.weight (21128, 768)

原始的hunggingface模型，保存模型参数为numpy，然后上面的numpy版的gpt-2就可以加载了

import numpy as np

from transformers import BertTokenizer, GPT2LMHeadModel, TextGenerationPipeline
tokenizer = BertTokenizer.from_pretrained("uer/gpt2-chinese-cluecorpussmall")
model = GPT2LMHeadModel.from_pretrained("uer/gpt2-chinese-cluecorpussmall")
text_generator = TextGenerationPipeline(model, tokenizer)
print(text_generator("今天是个好日子", max_length=20, do_sample=True))

print(model)

# 打印BERT模型的权重维度
# for name, param in model.named_parameters():
#     print(name, param.data.shape)

# print(model.lm_head.weight)
# print(model.lm_head.bias)

# # # 保存模型参数为NumPy格式
model_params = {name: param.data.cpu().numpy() for name, param in model.named_parameters()}
model_params["lm_head.weight"] = model.lm_head.weight.data.cpu().numpy()
np.savez('gpt2_model_params.npz', **model_params)
# model_params