Dask 将 function 应用于 dataframe 返回相同的结果

Question

当我在正常循环中将 function 应用于每个 dask dataframe 时：

stats = [run((key, value)) for key, value in tqdm.tqdm(routes_to_process.items())]
stats = {key: value for key, value in stats}

stats_df

我对每个 dataframe 得到不同的结果：

{'/R00_Y2011_0/Data_0001_Wings_H16000_F550.csv': {'total_time': Timedelta('13 days 06:00:00'),
  'wing_adjust_freq_mins': 15.0,
  'TotalTimeInMotion_parallel_mean': 1.2554810767556184,
  'TotalTimeInMotion_parallel_std': 1.938469269213107,
  'TotalTimeInMotion_parallel_95th': 4.919199116216657,
  'TotalTimeInMotion_parallel_max': 24.971773010775486,
  'TotalTimeInMotion_single_mean': 2.070414732378637,
  'TotalTimeInMotion_single_std': 3.110775531046329,
  'TotalTimeInMotion_single_95th': 7.7415319509222,
  'TotalTimeInMotion_single_max': 37.46848468358555},
 '/R00_Y2011_0/Data_0089_Wings_H16000_F550.csv': {'total_time': Timedelta('13 days 05:45:00'),
  'wing_adjust_freq_mins': 15.0,
  'TotalTimeInMotion_parallel_mean': 1.4529180621391111,
  'TotalTimeInMotion_parallel_std': 1.6725803825097267,
  'TotalTimeInMotion_parallel_95th': 4.844115032412909,
  'TotalTimeInMotion_parallel_max': 11.713955279708241,
  'TotalTimeInMotion_single_mean': 2.3589357740318952,
  'TotalTimeInMotion_single_std': 2.6615559537471416,
  'TotalTimeInMotion_single_95th': 7.704699349608058,
  'TotalTimeInMotion_single_max': 20.9864655817048},
 '/R00_Y2011_0/Data_0178_Wings_H16000_F550.csv': {'total_time': Timedelta('13 days 06:00:00'),
  'wing_adjust_freq_mins': 15.0,
  'TotalTimeInMotion_parallel_mean': 1.197378736624615,
  'TotalTimeInMotion_parallel_std': 1.7912324573518639,
  'TotalTimeInMotion_parallel_95th': 3.9983496355992054,
  'TotalTimeInMotion_parallel_max': 29.289081453498962,
  'TotalTimeInMotion_single_mean': 1.993188241820573,
  'TotalTimeInMotion_single_std': 2.885638510182584,
  'TotalTimeInMotion_single_95th': 6.9149671451086965,
  'TotalTimeInMotion_single_max': 46.73164328462062},
 '/R00_Y2011_0/Data_0266_Wings_H16000_F550.csv': {'total_time': Timedelta('13 days 06:15:00'),
  'wing_adjust_freq_mins': 15.0,
  'TotalTimeInMotion_parallel_mean': 0.8902764238240006,
  'TotalTimeInMotion_parallel_std': 1.0558873949196226,
  'TotalTimeInMotion_parallel_95th': 2.8579851928420603,
  'TotalTimeInMotion_parallel_max': 10.951810428266235,
  'TotalTimeInMotion_single_mean': 1.5333169994564122,
  'TotalTimeInMotion_single_std': 1.8294318193945236,
  'TotalTimeInMotion_single_95th': 4.79554414876004,
  'TotalTimeInMotion_single_max': 19.68630214945556},
 '/R00_Y2011_0/Data_0355_Wings_H16000_F550.csv': {'total_time': Timedelta('13 days 05:45:00'),
  'wing_adjust_freq_mins': 15.0,
  'TotalTimeInMotion_parallel_mean': 1.178448380566181,
  'TotalTimeInMotion_parallel_std': 2.3450293462261245,
  'TotalTimeInMotion_parallel_95th': 4.4953148097942774,
  'TotalTimeInMotion_parallel_max': 30.048903002576534,
  'TotalTimeInMotion_single_mean': 1.9654074975262181,
  'TotalTimeInMotion_single_std': 3.7519423792380233,
  'TotalTimeInMotion_single_95th': 6.873441025809852,
  'TotalTimeInMotion_single_max': 43.04718729546469}}

当我使用 dask 时：

L = client.map(run, routes_to_process.items())
res = client.gather(L)

我得到每个相同的结果：

[('/R00_Y2011_0/Data_0001_Wings_H16000_F550.csv',
  {'total_time': Timedelta('13 days 06:00:00'),
   'wing_adjust_freq_mins': 15.0,
   'TotalTimeInMotion_parallel_mean': 1.2554810767556184,
   'TotalTimeInMotion_parallel_std': 1.938469269213107,
   'TotalTimeInMotion_parallel_95th': 4.919199116216657,
   'TotalTimeInMotion_parallel_max': 24.971773010775486,
   'TotalTimeInMotion_single_mean': 2.070414732378637,
   'TotalTimeInMotion_single_std': 3.110775531046329,
   'TotalTimeInMotion_single_95th': 7.7415319509222,
   'TotalTimeInMotion_single_max': 37.46848468358555}),
 ('/R00_Y2011_0/Data_0089_Wings_H16000_F550.csv',
  {'total_time': Timedelta('13 days 06:00:00'),
   'wing_adjust_freq_mins': 15.0,
   'TotalTimeInMotion_parallel_mean': 1.2554810767556184,
   'TotalTimeInMotion_parallel_std': 1.938469269213107,
   'TotalTimeInMotion_parallel_95th': 4.919199116216657,
   'TotalTimeInMotion_parallel_max': 24.971773010775486,
   'TotalTimeInMotion_single_mean': 2.070414732378637,
   'TotalTimeInMotion_single_std': 3.110775531046329,
   'TotalTimeInMotion_single_95th': 7.7415319509222,
   'TotalTimeInMotion_single_max': 37.46848468358555}),
 ('/R00_Y2011_0/Data_0178_Wings_H16000_F550.csv',
  {'total_time': Timedelta('13 days 06:00:00'),
   'wing_adjust_freq_mins': 15.0,
   'TotalTimeInMotion_parallel_mean': 1.2554810767556184,
   'TotalTimeInMotion_parallel_std': 1.938469269213107,
   'TotalTimeInMotion_parallel_95th': 4.919199116216657,
   'TotalTimeInMotion_parallel_max': 24.971773010775486,
   'TotalTimeInMotion_single_mean': 2.070414732378637,
   'TotalTimeInMotion_single_std': 3.110775531046329,
   'TotalTimeInMotion_single_95th': 7.7415319509222,
   'TotalTimeInMotion_single_max': 37.46848468358555}),
 ('/R00_Y2011_0/Data_0266_Wings_H16000_F550.csv',
  {'total_time': Timedelta('13 days 06:00:00'),
   'wing_adjust_freq_mins': 15.0,
   'TotalTimeInMotion_parallel_mean': 1.2554810767556184,
   'TotalTimeInMotion_parallel_std': 1.938469269213107,
   'TotalTimeInMotion_parallel_95th': 4.919199116216657,
   'TotalTimeInMotion_parallel_max': 24.971773010775486,
   'TotalTimeInMotion_single_mean': 2.070414732378637,
   'TotalTimeInMotion_single_std': 3.110775531046329,
   'TotalTimeInMotion_single_95th': 7.7415319509222,
   'TotalTimeInMotion_single_max': 37.46848468358555}),
 ('/R00_Y2011_0/Data_0355_Wings_H16000_F550.csv',
  {'total_time': Timedelta('13 days 06:00:00'),
   'wing_adjust_freq_mins': 15.0,
   'TotalTimeInMotion_parallel_mean': 1.2554810767556184,
   'TotalTimeInMotion_parallel_std': 1.938469269213107,
   'TotalTimeInMotion_parallel_95th': 4.919199116216657,
   'TotalTimeInMotion_parallel_max': 24.971773010775486,
   'TotalTimeInMotion_single_mean': 2.070414732378637,
   'TotalTimeInMotion_single_std': 3.110775531046329,
   'TotalTimeInMotion_single_95th': 7.7415319509222,
   'TotalTimeInMotion_single_max': 37.46848468358555})]

尽管文件名不同。 我怎样才能防止这种情况发生？

Answer 1

从这些信息中不清楚routes_to_process里面有什么，但一个潜在的罪魁祸首是client.map和client.submit中pure的默认选项是None 。 这意味着 function 预计会为相同的输入返回相同的结果（这是routes_to_process的内容很重要的地方。尝试的一件事是添加pure=False ：

L = client.map(run, routes_to_process.items(), pure=False)
res = client.gather(L)

另一个潜在的问题是，在顺序执行中，您使用run((key, value))调用 function，并且双括号表明您将一个元组传递给 function，而client.map版本将传递两个 arguments。取决于关于您的 function 是如何定义的，这可能会导致静默失败（因为额外的输入被**args吸收）。 如果这是问题所在，可能值得更正 function 的定义。