现实生活中的 df 是一个无法加载到驱动程序内存中的海量数据帧。这可以使用常规或 pandas udf 来完成吗?
# Code to generate a sample dataframe
from pyspark.sql import functions as F
from pyspark.sql.types import *
import pandas as pd
import numpy as np
sample = [['123',[[0,1,0,0,0,1,1,1,1,1,1,0,1,0,0,0,1,1,1,1,1,1], [0,1,0,0,0,1,1,1,1,1,1,0,1,0,0,0,1,1,1,1,1,1]]],
['345',[[1,0,0,0,0,1,1,1,0,1,1,0,1,0,0,0,1,1,1,1,1,1], [0,1,0,0,0,1,1,1,1,1,1,0,1,0,0,0,1,1,1,1,1,1]]],
['425',[[1,1,0,0,0,1,0,1,1,1,1,0,1,0,0,0,1,1,1,1,1,1],[0,1,0,0,0,1,1,1,1,1,1,0,1,0,0,0,1,1,1,1,1,1]]],
]
df = spark.createDataFrame(sample,["id", "data"])
这是需要在不依赖驱动程序内存的情况下并行化的逻辑。
输入:Spark 数据帧输出:要输入 horovod 的 numpy 数组(类似这样的:https ://docs.databricks.com/applications/deep-learning/distributed-training/mnist-tensorflow-keras.html )
pandas_df = df.toPandas() # Not possible in real life
data_array = np.asarray(list(pandas_df.data.values))
data_array = data_array.reshape(data_array.shape[0], data_array.shape[1], -1, 1, order='F')
data_array = data_array.reshape(data_array.shape[0],data_array.shape[1],-1,1,1,order="F").transpose(0,1,3,2,-1)
# Some more numpy specific transformations ..
这是一种不起作用的方法:
@pandas_udf(ArrayType(IntegerType()), PandasUDFType.SCALAR)
def generate_feature(x):
data_array = np.asarray(x)
data_array = data_array.reshape(data_array.shape[0], ..
...
return pd.Series(data_array)
df = df.withColumn("data_array", generate_feature(df.data))