gcForest 官方程式碼詳解
1.介紹
gcForest v1.1.1是gcForest的一個官方託管在GitHub上的版本,是由Ji Feng(Deep Forest的paper的作者之一)維護和開發,該版本支援Python3.5,且有類似於Scikit-Learn的API介面風格,在該專案中提供了一些呼叫例子,目前支援的基分類器有RandomForestClassifier,XGBClassifer,ExtraTreesClassifier,LogisticRegression,SGDClassifier如果採用XGBoost的基分類器還可以使用GPU
本文采用的是v1.1.1版本,github地址https://github.com/kingfengji/gcForest
如果想增加其他基分類器,可以在模組中的lib/gcforest/estimators/__init__.py
中新增
使用該模組需要依賴安裝如下模組:
- argparse
- joblib
- keras
- psutil
- scikit-learn>=0.18.1
- scipy
- simplejson
- tensorflow
- xgboost
2.API呼叫樣例
這裡先列出gcForest提供的API介面:
-
fit_tranform(X_train,y_train) 是gcForest模型最後一層每個估計器預測的概率concatenated的結果
-
fit_transform(X_train,y_train,X_test=x_test,y_test=y_test) 測試資料的準確率在訓練的過程中也會被記錄下來
-
set_keep_model_mem(False) 如果你的快取不夠,把該引數設定成False(預設為True),如果設定成False,你需要使用fit_transform(X_train,y_train,X_test=x_test,y_test=y_test)來評估你的模型
-
predict(X_test) # 模型預測
-
transform(X_test)
程式碼主要分為兩部分:examples資料夾下是主程式碼.py和配置檔案.json;libs資料夾下是程式碼中用到的庫
主程式碼的實現
最簡單的呼叫gcForest的方式如下:
# 匯入必要的模組
from gcforest.gcforest import GCForest
# 初始化一個gcForest物件
gc = GCForest(config) # config是一個字典結構
# gcForest模型最後一層每個估計器預測的概率concatenated的結果
X_train_enc = gc.fit_transform(X_train,y_train)
# 測試集的預測
y_pred = gc.predict(X_test)
lib庫的詳解
gcforest.py 整個框架的實現
fgnet.py 多粒度部分,FineGrained的實現
cascade/cascade_classifier 級聯分類器的實現
datasets/.... 包含一系列資料集的定義
estimator/... 包含決策樹在進行評估用到的函式(多種分類器的預估)
layer/... 包含不同的層操作,如連線、池化、滑窗等
utils/.. 包含各種功能函式,譬如計算準確率、win_vote、win_avg、get_windows等
json配置檔案的詳解
引數介紹
- max_depth: 決策樹最大深度。預設為"None",決策樹在建立子樹的時候不會限制子樹的深度這樣建樹時,會使每一個葉節點只有一個類別,或是達到min_samples_split。一般來說,資料少或者特徵少的時候可以不管這個值。如果模型樣本量多,特徵也多的情況下,推薦限制這個最大深度,具體的取值取決於資料的分佈。常用的可以取值10-100之間。
- estimators表示選擇的分類器
- n_estimators 為森林裡的樹的數量
- n_jobs: int (default=1)
The number of jobs to run in parallel for any Random Forest fit and predict.
If -1, then the number of jobs is set to the number of cores.
訓練的配置,分三類情況:
- 採用預設的模型
def get_toy_config():
config = {}
ca_config = {}
ca_config["random_state"] = 0 # 0 or 1
ca_config["max_layers"] = 100 #最大的層數,layer對應論文中的level
ca_config["early_stopping_rounds"] = 3 #如果出現某層的三層以內的準確率都沒有提升,層中止
ca_config["n_classes"] = 3 #判別的類別數量
ca_config["estimators"] = []
ca_config["estimators"].append(
{"n_folds": 5, "type": "XGBClassifier", "n_estimators": 10, "max_depth": 5,
"objective": "multi:softprob", "silent": True, "nthread": -1, "learning_rate": 0.1} )
ca_config["estimators"].append({"n_folds": 5, "type": "RandomForestClassifier", "n_estimators": 10, "max_depth": None, "n_jobs": -1})
ca_config["estimators"].append({"n_folds": 5, "type": "ExtraTreesClassifier", "n_estimators": 10, "max_depth": None, "n_jobs": -1})
ca_config["estimators"].append({"n_folds": 5, "type": "LogisticRegression"})
config["cascade"] = ca_config #共使用了四個基學習器
return config
支援的基本分類器:
RandomForestClassifier
XGBClassifier
ExtraTreesClassifier
LogisticRegression
SGDClassifier
你可以通過下述方式手動新增任何分類器:
lib/gcforest/estimators/__init__.py
- 只有級聯(cascade)部分
{
"cascade": {
"random_state": 0,
"max_layers": 100,
"early_stopping_rounds": 3,
"n_classes": 10,
"estimators": [
{"n_folds":5,"type":"XGBClassifier","n_estimators":10,"max_depth":5,"objective":"multi:softprob", "silent":true, "nthread":-1, "learning_rate":0.1},
{"n_folds":5,"type":"RandomForestClassifier","n_estimators":10,"max_depth":null,"n_jobs":-1},
{"n_folds":5,"type":"ExtraTreesClassifier","n_estimators":10,"max_depth":null,"n_jobs":-1},
{"n_folds":5,"type":"LogisticRegression"}
]
}
}
- “multi fine-grained + cascade” 兩部分
滑動視窗的大小: {[d/16], [d/8], [d/4]},d代表輸入特徵的數量;
"look_indexs_cycle": [
[0, 1],
[2, 3],
[4, 5]]
代表級聯多粒度的方式,第一層級聯0、1森林的輸出,第二層級聯2、3森林的輸出,第三層級聯4、5森林的輸出
{
"net":{
"outputs": ["pool1/7x7/ets", "pool1/7x7/rf", "pool1/10x10/ets", "pool1/10x10/rf", "pool1/13x13/ets", "pool1/13x13/rf"],
"layers":[
// win1/7x7
{
"type":"FGWinLayer",
"name":"win1/7x7",
"bottoms": ["X","y"],
"tops":["win1/7x7/ets", "win1/7x7/rf"],
"n_classes": 10,
"estimators": [
{"n_folds":3,"type":"ExtraTreesClassifier","n_estimators":20,"max_depth":10,"n_jobs":-1,"min_samples_leaf":10},
{"n_folds":3,"type":"RandomForestClassifier","n_estimators":20,"max_depth":10,"n_jobs":-1,"min_samples_leaf":10}
],
"stride_x": 2,
"stride_y": 2,
"win_x":7,
"win_y":7
},
// win1/10x10
{
"type":"FGWinLayer",
"name":"win1/10x10",
"bottoms": ["X","y"],
"tops":["win1/10x10/ets", "win1/10x10/rf"],
"n_classes": 10,
"estimators": [
{"n_folds":3,"type":"ExtraTreesClassifier","n_estimators":20,"max_depth":10,"n_jobs":-1,"min_samples_leaf":10},
{"n_folds":3,"type":"RandomForestClassifier","n_estimators":20,"max_depth":10,"n_jobs":-1,"min_samples_leaf":10}
],
"stride_x": 2,
"stride_y": 2,
"win_x":10,
"win_y":10
},
// win1/13x13
{
"type":"FGWinLayer",
"name":"win1/13x13",
"bottoms": ["X","y"],
"tops":["win1/13x13/ets", "win1/13x13/rf"],
"n_classes": 10,
"estimators": [
{"n_folds":3,"type":"ExtraTreesClassifier","n_estimators":20,"max_depth":10,"n_jobs":-1,"min_samples_leaf":10},
{"n_folds":3,"type":"RandomForestClassifier","n_estimators":20,"max_depth":10,"n_jobs":-1,"min_samples_leaf":10}
],
"stride_x": 2,
"stride_y": 2,
"win_x":13,
"win_y":13
},
// pool1
{
"type":"FGPoolLayer",
"name":"pool1",
"bottoms": ["win1/7x7/ets", "win1/7x7/rf", "win1/10x10/ets", "win1/10x10/rf", "win1/13x13/ets", "win1/13x13/rf"],
"tops": ["pool1/7x7/ets", "pool1/7x7/rf", "pool1/10x10/ets", "pool1/10x10/rf", "pool1/13x13/ets", "pool1/13x13/rf"],
"pool_method": "avg",
"win_x":2,
"win_y":2
}
]
},
"cascade": {
"random_state": 0,
"max_layers": 100,
"early_stopping_rounds": 3,
"look_indexs_cycle": [
[0, 1],
[2, 3],
[4, 5]
],
"n_classes": 10,
"estimators": [
{"n_folds":5,"type":"ExtraTreesClassifier","n_estimators":1000,"max_depth":null,"n_jobs":-1},
{"n_folds":5,"type":"RandomForestClassifier","n_estimators":1000,"max_depth":null,"n_jobs":-1}
]
}
}
3.MNIST樣例
下面我們使用MNIST資料集來演示gcForest的使用及程式碼的詳細說明:
# 匯入必要的模組
import argparse # 命令列引數呼叫模組
import numpy as np
import sys
from keras.datasets import mnist # MNIST資料集
import pickle
from sklearn.ensemble import RandomForestClassifier
from sklearn.metrics import accuracy_score
sys.path.insert(0, "lib")
from gcforest.gcforest import GCForest
from gcforest.utils.config_utils import load_json
def parse_args():
'''
解析終端命令列引數(model)
'''
parser = argparse.ArgumentParser()
parser.add_argument("--model", dest="model", type=str, default=None,
help="gcfoest Net Model File")
args = parser.parse_args()
return args
def get_toy_config():
'''
生成級聯結構的相關結構
'''
config = {}
ca_config = {}
ca_config["random_state"] = 0
ca_config["max_layers"] = 100
ca_config["early_stopping_rounds"] = 3
ca_config["n_classes"] = 10
ca_config["estimators"] = []
ca_config["estimators"].append(
{"n_folds": 5, "type": "XGBClassifier", "n_estimators": 10,
"max_depth": 5,"objective": "multi:softprob", "silent":
True, "nthread": -1, "learning_rate": 0.1} )
ca_config["estimators"].append({"n_folds": 5, "type": "RandomForestClassifier",
"n_estimators": 10, "max_depth": None, "n_jobs": -1})
ca_config["estimators"].append({"n_folds": 5, "type": "ExtraTreesClassifier",
"n_estimators": 10, "max_depth": None, "n_jobs": -1})
ca_config["estimators"].append({"n_folds": 5, "type": "LogisticRegression"})
config["cascade"] = ca_config
return config
# get_toy_config()生成的結構,如下所示:
'''
{
"cascade": {
"random_state": 0,
"max_layers": 100,
"early_stopping_rounds": 3,
"n_classes": 10,
"estimators": [
{"n_folds":5,"type":"XGBClassifier","n_estimators":10,"max_depth":5,
"objective":"multi:softprob", "silent":true,
"nthread":-1, "learning_rate":0.1},
{"n_folds":5,"type":"RandomForestClassifier","n_estimators":10,
"max_depth":null,"n_jobs":-1},
{"n_folds":5,"type":"ExtraTreesClassifier","n_estimators":10,
"max_depth":null,"n_jobs":-1},
{"n_folds":5,"type":"LogisticRegression"}
]
}
}
'''
if __name__ == "__main__":
args = parse_args()
if args.model is None:
config = get_toy_config()
else:
config = load_json(args.model)
gc = GCForest(config)
# 如果模型消耗太大記憶體,可以使用如下命令使得gcforest不儲存在記憶體中
# gc.set_keep_model_in_mem(False), 預設情況下是True.
(X_train, y_train), (X_test, y_test) = mnist.load_data()
# X_train, y_train = X_train[:2000], y_train[:2000]
# np.newaxis相當於增加了一個維度
X_train = X_train[:, np.newaxis, :, :]
X_test = X_test[:, np.newaxis, :, :]
X_train_enc = gc.fit_transform(X_train, y_train)
# X_enc是gcForest模型最後一層每個估計器預測的概率concatenated的結果
# X_enc.shape =
# (n_datas, n_estimators * n_classes): 如果是級聯結構
# (n_datas, n_estimators * n_classes, dimX, dimY): 如果只有多粒度掃描結構
# 可以在fit_transform方法中加入X_test,y_test,這樣測試資料的準確率在訓練的過程中
# 也會被記錄下來。
# X_train_enc, X_test_enc =
gc.fit_transform(X_train, y_train, X_test=X_test, y_test=y_test)
# 注意: 如果設定了gc.set_keep_model_in_mem(True),必須使用
# gc.fit_transform(X_train, y_train, X_test=X_test, y_test=y_test)
# 評估模型
# 測試集預測與評估
y_pred = gc.predict(X_test)
acc = accuracy_score(y_test, y_pred)
print("Test Accuracy of GcForest = {:.2f} %".format(acc * 100))
# 可以使用gcForest得到的X_enc資料進行其他模型的訓練比如xgboost/RF
# 資料的concat
X_test_enc = gc.transform(X_test)
X_train_enc = X_train_enc.reshape((X_train_enc.shape[0], -1))
X_test_enc = X_test_enc.reshape((X_test_enc.shape[0], -1))
X_train_origin = X_train.reshape((X_train.shape[0], -1))
X_test_origin = X_test.reshape((X_test.shape[0], -1))
X_train_enc = np.hstack((X_train_origin, X_train_enc))
X_test_enc = np.hstack((X_test_origin, X_test_enc))
print("X_train_enc.shape={}, X_test_enc.shape={}".format(X_train_enc.shape,
X_test_enc.shape))
# 訓練一個RF
clf = RandomForestClassifier(n_estimators=1000, max_depth=None, n_jobs=-1)
clf.fit(X_train_enc, y_train)
y_pred = clf.predict(X_test_enc)
acc = accuracy_score(y_test, y_pred)
print("Test Accuracy of Other classifier using
gcforest's X_encode = {:.2f} %".format(acc * 100))
# 模型寫入pickle檔案
with open("test.pkl", "wb") as f:
pickle.dump(gc, f, pickle.HIGHEST_PROTOCOL)
# 載入訓練的模型
with open("test.pkl", "rb") as f:
gc = pickle.load(f)
y_pred = gc.predict(X_test)
acc = accuracy_score(y_test, y_pred)
print("Test Accuracy of GcForest (save and load) = {:.2f} %".format(acc * 100))
這裡需要注意的是gcForest不但可以對傳統的結構化的2維資料建模,還可以對非結構化的資料比如影象,序列化的文字資料,音訊資料等進行建模,但要注意資料維度的設定:
-
如果僅使用級聯結構,X_train,X_test對於2-D陣列其維度為(n_samples,n_features);3-D或4-D陣列會自動reshape為2-D,例如MNIST資料(60000,28,28)會reshape為(60000,784),(60000,3,28,28)會reshape為(60000,2352)。
-
如果使用多粒度掃描結構,X_train,X_test必須是4—D的陣列,影象資料其維度是(n_samples,n_channels,n_height,n_width);序列資料其維度為(n_smaples,n_features,seq_len,1),例如對於IMDB資料,n_features為1,對於音訊MFCC特徵,其n_features可以為13,26等。
上述程式碼可以通過兩種方式執行:
- 一種方式是通過json檔案定義模型結構,比如級聯森林結構,只需要寫一個json檔案如程式碼中顯示的結構,然後通過命令列執行
python examples/demo_mnist.py --model examples/demo_mnist-gc.json
就可以完成訓練;如果既使用多粒度掃面又使用級聯結構,那麼需要同時把多粒度掃描的結構定義出來。 - 定義好的json可以通過模組中的load_json()方法載入,然後作為引數初始化模型,如下:
config = load_json(your_json_file)
gc = GCForest(config)
- 另一種方式是直接通過Python程式碼定義模型結構,實際上模型結構就是一個字典資料結構,即是上述程式碼中的
get_toy_config()
方法。