ソースコード
def reduce_mem_usage(train_data):
""" iterate through all the columns of a dataframe and modify the data type
to reduce memory usage.
"""
start_mem = train_data.memory_usage().sum() / 1024**2
print('Memory usage of dataframe is {:.2f} MB'.format(start_mem))
for col in train_data.columns:
col_type = train_data[col].dtype
if col_type != object:
c_min = train_data[col].min()
c_max = train_data[col].max()
if str(col_type)[:3] == 'int':
if c_min > np.iinfo(np.int8).min and c_max < np.iinfo(np.int8).max:
train_data[col] = train_data[col].astype(np.int8)
elif c_min > np.iinfo(np.int16).min and c_max < np.iinfo(np.int16).max:
train_data[col] = train_data[col].astype(np.int16)
elif c_min > np.iinfo(np.int32).min and c_max < np.iinfo(np.int32).max:
train_data[col] = train_data[col].astype(np.int32)
elif c_min > np.iinfo(np.int64).min and c_max < np.iinfo(np.int64).max:
train_data[col] = train_data[col].astype(np.int64)
else:
if c_min > np.finfo(np.float16).min and c_max < np.finfo(np.float16).max:
train_data[col] = train_data[col].astype(np.float16)
elif c_min > np.finfo(np.float32).min and c_max < np.finfo(np.float32).max:
train_data[col] = train_data[col].astype(np.float32)
else:
train_data[col] = train_data[col].astype(np.float64)
else:
train_data[col] = train_data[col].astype('category')
end_mem = train_data.memory_usage().sum() / 1024**2
print('Memory usage after optimization is: {:.2f} MB'.format(end_mem))
print('Decreased by {:.1f}%'.format(100 * (start_mem - end_mem) / start_mem))
return train_data
呼び出し
df = reduce_mem_usage(df)
出力
Memory usage of dataframe is 109.14 MB
Memory usage after optimization is: 79.94 MB
Decreased by 26.8%