讨论和总结 树模型 的三种序列化 方式的区别（模型存储大小、序列化所用内存、序列化速度）...
一、前言
本文总结常用树模型： rf，xgboost，catboost和lightgbm等模型的保存和加载（序列化和反序列化）的多种方式，并对多种方式从运行内存的使用和存储大小做对比
二、模型
2.1 安装环境
pip install xgboost
pip install lightgbm
pip install catboost
pip install scikit-learn可以指定版本也可以不指定，直接下载可获取最新的pkg
2.2 模型运行例子
针对iris数据集的多分类任务
import xgboost as xgb
from catboost import CatBoostClassifier
from sklearn.datasets import load_iris
from sklearn.metrics import accuracy_score
from sklearn.model_selection import train_test_splitimport lightgbm as lgb
from sklearn.ensemble import RandomForestClassifieriris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)# xgb
xgb_train = xgb.DMatrix(X_train, y_train)
xgb_test = xgb.DMatrix(X_test, y_test)
xgb_params = {'objective': 'multi:softmax', 'eval_metric': 'mlogloss', 'num_class': 3, 'verbosity': 0}
xgb_model = xgb.train(xgb_params, xgb_train)
y_pred = xgb_model.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)# lgb
lgb_train = lgb.Dataset(X_train, y_train)
lgb_eval = lgb.Dataset(X_test, y_test, reference=lgb_train)
params = {'boosting_type': 'gbdt','objective': 'multiclass','num_class': 3,'metric': 'multi_logloss','num_leaves': 31,'learning_rate': 0.05,'feature_fraction': 0.9
}
gbm = lgb.train(params, lgb_train, num_boost_round=100, valid_sets=[lgb_eval], early_stopping_rounds=5)
y_pred = gbm.predict(X_test, num_iteration=gbm.best_iteration)
y_pred = [list(x).index(max(x)) for x in y_pred]
lgb_acc = accuracy_score(y_test, y_pred)# rf
rf = RandomForestClassifier()
rf.fit(X_train, y_train)
y_pred = rf.predict(X_test)
rf_acc = accuracy_score(y_test, y_pred)# catboost
cat_boost_model = CatBoostClassifier(depth=9, learning_rate=0.01,loss_function='MultiClass', custom_metric=['AUC'],eval_metric='MultiClass', random_seed=1996)cat_boost_model.fit(X_train, y_train, eval_set=(X_test, y_test), use_best_model=True, early_stopping_rounds=1000)
y_pred = cat_boost_model.predict(X_test)
cat_acc = accuracy_score(y_test, y_pred)print(xgb_acc, lgb_acc, rf_acc, cat_acc)2.3 运行内存计算
def cal_current_memory():# 获取当前进程内存占用。pid = os.getpid()p = psutil.Process(pid)info = p.memory_full_info()memory_used = info.uss / 1024. / 1024. / 1024.return {'memoryUsed': memory_used}获取当前进程的pid，通过pid来定向查询memory的使用
三、保存和加载
主要有三种方法：
jsonpickle
pickle
模型api
3.1 jsonpickle
jsonpickle 是一个 Python 序列化和反序列化库，它可以将 Python 对象转换为 JSON 格式的字符串，或将 JSON 格式的字符串转换为 Python 对象。
调用jsonpickle.encode即可序列化，decode进行反序列化
以xgb为例
保存：
iris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)# xgb
xgb_train = xgb.DMatrix(X_train, y_train)
xgb_test = xgb.DMatrix(X_test, y_test)
xgb_params = {'objective': 'multi:softmax', 'eval_metric': 'mlogloss', 'num_class': 3, 'verbosity': 0}
xgb_model = xgb.train(xgb_params, xgb_train)
y_pred = xgb_model.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)xgb_str = jsonpickle.encode(xgb_model)
with open(f'{save_dir}/xgb_model_jsonpickle.json', 'w') as f:f.write(xgb_str)加载：
save_dir = './models'iris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)xgb_test = xgb.DMatrix(X_test, y_test)with open(f'{save_dir}/xgb_model_jsonpickle.json', 'r') as f:xgb_model_jsonpickle = f.read()
xgb_model_jsonpickle = jsonpickle.decode(xgb_model_jsonpickle)
y_pred = xgb_model_jsonpickle.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)
print(xgb_acc)这样就完成了模型的保存和加载
优势
模型加载过程不需要重新实例化，直接jsonpickle.decode模型文件即可直接获得模型
获得的模型文件是json格式，便于各种编程语言和平台之间的数据交换，方便实现不同系统之间的数据传输和共享
劣势
在处理大型或者复杂的模型时，序列化过程可能会出现性能问题（占用更多的memory）
模型文件存储空间比较大
3.2 pickle
pickle 是 Python 的一种序列化和反序列化模块，可以将 Python 对象转换为字节流，也可以将字节流转换为 Python 对象，进而实现 Python 对象的持久化存储和恢复。（模型也是个对象）
调用pickle.dump/dumps即可序列化，pickle.load/loads进行反序列化（其中dump直接将序列化文件保存，二dumps则是返回序列化后的bytes文件，load和loads亦然）
这里可以查看和其他python方法的对比：https://docs.python.org/zh-cn/3/library/pickle.html
以xgb为例
保存：
iris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)# xgb
xgb_train = xgb.DMatrix(X_train, y_train)
xgb_test = xgb.DMatrix(X_test, y_test)
xgb_params = {'objective': 'multi:softmax', 'eval_metric': 'mlogloss', 'num_class': 3, 'verbosity': 0}
xgb_model = xgb.train(xgb_params, xgb_train)
y_pred = xgb_model.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)with open(f'{save_dir}/xgb_model_pickle.pkl', 'wb') as f:pickle.dump(xgb_model, f)加载：
save_dir = './models'iris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)xgb_test = xgb.DMatrix(X_test, y_test)with open(f'{save_dir}/xgb_model_pickle.pkl', 'rb') as f:xgb_model_pickle = pickle.load(f)
y_pred = xgb_model_pickle.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)
print(xgb_acc)优势
模型加载过程同样不需要重新实例化，这点和jsonpickle一样
序列化文件相比于jsonpickle小非常的多，且读取和保存都会更快
劣势
在处理大型或者复杂的对象时，可能会出现性能问题（占用更多的memory）
不是json格式，很难跨平台和语言使用
3.3 模型自带
以xgb为例
保存
iris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)# xgb
xgb_train = xgb.DMatrix(X_train, y_train)
xgb_test = xgb.DMatrix(X_test, y_test)
xgb_params = {'objective': 'multi:softmax', 'eval_metric': 'mlogloss', 'num_class': 3, 'verbosity': 0}
xgb_model = xgb.train(xgb_params, xgb_train)
y_pred = xgb_model.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)model_path = f'{save_dir}/xgb_model_self.bin' #也可以是json格式，但最终文件大小有区别
xgb_model.save_model(model_path)加载
save_dir = './models'iris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)xgb_test = xgb.DMatrix(X_test, y_test)xgb_model_self = xgb.Booster()
xgb_model_self.load_model(f'{save_dir}/xgb_model_self.bin')
y_pred = xgb_model_self.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)
print(xgb_acc)更多文档参考：https://xgboost.readthedocs.io/en/stable/tutorials/saving_model.html
优势
只保存了模型的参数文件（包含树结构和需要模型参数比如 the objective function等）， 模型文件较小
序列化过程中的运行内存所占不多
也可以保存json的形式（在XGBoost 1.0.0之后推荐以json的方式保存）
劣势
需要在加载模型之前创建模型的实例。
四、实验
以下主要还是针对较小的模型来做的实验
4.1 模型存储大小对比实验
_jsonpickle就是用jsonpickle方法序列化的模型文件
_pickle是用pickle方法序列化的模型文件
_self就是利用自身的save model的方法保存的模型文件
可以看出来是 jsonpickle> pickle > self 的关系
4.2 运行的memory对比实验
通过对序列化前后的memory做监控，例如xgb(只考虑序列化，去掉文件写入所需要的memory)：
print("before:", cal_current_memory())
model_path = f'{save_dir}/xgb_model_self.bin'
xgb_model.save_model(model_path)
print("after:", cal_current_memory())运行得到：
before: {'memoryUsed': 0.1490936279296875}
after: {'memoryUsed': 0.14911270141601562}print("before:", cal_current_memory())
pickle.dumps(xgb_model)
print("after:", cal_current_memory())运行得到：
before: {'memoryUsed': 0.1498260498046875}
after: {'memoryUsed': 0.14990234375}print("before:", cal_current_memory())
xgb_str = jsonpickle.encode(xgb_model)
print("after:", cal_current_memory())运行得到：
before: {'memoryUsed': 0.14917755126953125}
after: {'memoryUsed': 0.15140914916992188}可以看出来对于xgb模型，picklejson所需要的memory是其他两种方法的几十倍，而其余两种方法很相似
lgb的结果：
对应上述顺序：
self:
before: {'memoryUsed': 0.14953994750976562}
after {'memoryUsed': 0.14959716796875}
pickle:
before: {'memoryUsed': 0.14938735961914062}
after {'memoryUsed': 0.14946746826171875}
jsonpickle：
before: {'memoryUsed': 0.14945602416992188}
after {'memoryUsed': 0.14974594116210938}这里依然是jsonpickle大一些，但倍数小一些
catboost的结果：
self:
before: {'memoryUsed': 0.24615478515625}
after {'memoryUsed': 0.25492095947265625}
pickle:
before: {'memoryUsed': 0.2300567626953125}
after {'memoryUsed': 0.25820159912109375}
jsonpickle：
before: {'memoryUsed': 0.2452239990234375}
after {'memoryUsed': 0.272674560546875}4.3 序列化时间对比
因为catboost总体模型大小大一些，所以通过catboost才能更好的反应序列化的速度
self:
0.02413797378540039 s
pickle:
0.04681825637817383 s
jsonpickle：
0.3211638927459717 sjsonpickle的花费的时间会多一些
五、 总体代码
训练：
import base64
import json
import os
import pickle
import time
import jsonpickle
import psutil
import xgboost as xgb
from catboost import CatBoostClassifier
from sklearn.datasets import load_iris
from sklearn.metrics import accuracy_score
from sklearn.model_selection import train_test_splitimport lightgbm as lgb
from sklearn.ensemble import RandomForestClassifiersave_dir = "./models"def cal_current_memory():# 获取当前进程内存占用。pid = os.getpid()p = psutil.Process(pid)info = p.memory_full_info()memory_used = info.uss / 1024. / 1024. / 1024.return {'memoryUsed': memory_used}iris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)# xgb
xgb_train = xgb.DMatrix(X_train, y_train)
xgb_test = xgb.DMatrix(X_test, y_test)
xgb_params = {'objective': 'multi:softmax', 'eval_metric': 'mlogloss', 'num_class': 3, 'verbosity': 0}
xgb_model = xgb.train(xgb_params, xgb_train)
y_pred = xgb_model.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)
#
# print("before:", cal_current_memory())
# model_path = f'{save_dir}/xgb_model_self.bin'
# xgb_model.save_model(model_path)
# print("after", cal_current_memory())
with open(f'{save_dir}/xgb_model_pickle.pkl', 'wb') as f:pickle.dump(xgb_model, f)
print(cal_current_memory())
xgb_str = jsonpickle.encode(xgb_model)
with open(f'{save_dir}/xgb_model_jsonpickle.json', 'w') as f:f.write(xgb_str)
print(cal_current_memory())# lgb
lgb_train = lgb.Dataset(X_train, y_train)
lgb_eval = lgb.Dataset(X_test, y_test, reference=lgb_train)
params = {'boosting_type': 'gbdt','objective': 'multiclass','num_class': 3,'metric': 'multi_logloss','num_leaves': 31,'learning_rate': 0.05,'feature_fraction': 0.9
}
gbm = lgb.train(params, lgb_train, num_boost_round=100, valid_sets=[lgb_eval], early_stopping_rounds=5)
y_pred = gbm.predict(X_test, num_iteration=gbm.best_iteration)
y_pred = [list(x).index(max(x)) for x in y_pred]
lgb_acc = accuracy_score(y_test, y_pred)
#
# print("before:", cal_current_memory())
# model_path = f'{save_dir}/lgb_model_self.bin'
# gbm.save_model(model_path)
# print("after", cal_current_memory())with open(f'{save_dir}/lgb_model_pickle.pkl', 'wb') as f:pickle.dump(gbm, f)lgb_str = jsonpickle.encode(gbm)
with open(f'{save_dir}/lgb_model_jsonpickle.json', 'w') as f:f.write(lgb_str)# rf
rf = RandomForestClassifier()
rf.fit(X_train, y_train)
y_pred = rf.predict(X_test)
rf_acc = accuracy_score(y_test, y_pred)with open(f'{save_dir}/rf_model_pickle.pkl', 'wb') as f:pickle.dump(rf, f)rf_str = jsonpickle.encode(rf)
with open(f'{save_dir}/rf_model_jsonpickle.json', 'w') as f:f.write(rf_str)# catboost
cat_boost_model = CatBoostClassifier(depth=9, learning_rate=0.01,loss_function='MultiClass', custom_metric=['AUC'],eval_metric='MultiClass', random_seed=1996)cat_boost_model.fit(X_train, y_train, eval_set=(X_test, y_test), use_best_model=True, early_stopping_rounds=1000)
y_pred = cat_boost_model.predict(X_test)
cat_acc = accuracy_score(y_test, y_pred)# t = time.time()
# model_path = f'{save_dir}/cat_boost_model_self.bin'
# cat_boost_model.save_model(model_path)
# print("after", time.time() - t)# print("before:", cal_current_memory())
# model_path = f'{save_dir}/cat_boost_model_self.bin'
# cat_boost_model.save_model(model_path)
# print("after", cal_current_memory())
with open(f'{save_dir}/cat_boost_model_pickle.pkl', 'wb') as f:pickle.dump(cat_boost_model, f)cat_boost_model_str = jsonpickle.encode(cat_boost_model)
with open(f'{save_dir}/cat_boost_model_jsonpickle.json', 'w') as f:f.write(cat_boost_model_str)print(xgb_acc, lgb_acc, rf_acc, cat_acc)测试
import pickleimport jsonpickle
import psutil
import xgboost as xgb
from catboost import CatBoostClassifier
from sklearn.datasets import load_iris
from sklearn.metrics import accuracy_score
from sklearn.model_selection import train_test_split
import lightgbm as lgb
from sklearn.ensemble import RandomForestClassifiersave_dir = './models'iris = load_iris()
X = iris.data
y = iris.targetX_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=1996)xgb_test = xgb.DMatrix(X_test, y_test)xgb_model_self = xgb.Booster()
xgb_model_self.load_model(f'{save_dir}/xgb_model_self.bin')
y_pred = xgb_model_self.predict(xgb_test)
xgb_acc = accuracy_score(y_test, y_pred)
print(xgb_acc)# with open(f'{save_dir}/xgb_model_pickle.pkl', 'rb') as f:
# xgb_model_pickle = pickle.load(f)
# y_pred = xgb_model_pickle.predict(xgb_test)
# xgb_acc = accuracy_score(y_test, y_pred)
# print(xgb_acc)#
# with open(f'{save_dir}/xgb_model_jsonpickle.json', 'r') as f:
# xgb_model_jsonpickle = f.read()
# xgb_model_jsonpickle = jsonpickle.decode(xgb_model_jsonpickle)
# y_pred = xgb_model_jsonpickle.predict(xgb_test)
# xgb_acc = accuracy_score(y_test, y_pred)
# print(xgb_acc)ps：这里给出所有的代码，代码不多，但都写在一起了，比较粗糙，每个实验要记得把其他的对应代码注释掉。
六、总结
以上实验都是几次实验运行的结果的平均，如果想更有说服力，可以更多次实验取平均值来参考，整体的结果基本上没有差异。（还可以从更大的模型入手来讨论）
1. 对于图省事，并且想跨平台语言的话可以选择picklejson，但一定要有一定的memory预估，如果模型比较复杂比较大（可能一个模型class包含多种其他模型的对象），会占用非常大的memory，且模型文件也会非常大，但不需要对于每个单独的子模型做序列化，直接decode即可。
2. 对于要求省空间且运行内存的话，可以选择模型自身的保存方式（主要只保存模型参数文件），但对于这种方式，可能需要在模型的总class去实现序列化和反序列化方法（子模型都要实现，且每个都调用该模型的savemodel和loadmodel方法）
3. python下不考虑跨平台语言序列化和反序列可以直接考虑pickle的序列化方式，也比较省事。
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