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Posted to jira@arrow.apache.org by "Wes McKinney (Jira)" <ji...@apache.org> on 2020/06/26 15:59:00 UTC
[jira] [Assigned] (ARROW-8888) [Python] Heuristic in
dataframe_to_arrays that decides to multithread convert cause slow
conversions
[ https://issues.apache.org/jira/browse/ARROW-8888?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Wes McKinney reassigned ARROW-8888:
-----------------------------------
Assignee: Wes McKinney
> [Python] Heuristic in dataframe_to_arrays that decides to multithread convert cause slow conversions
> ----------------------------------------------------------------------------------------------------
>
> Key: ARROW-8888
> URL: https://issues.apache.org/jira/browse/ARROW-8888
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Affects Versions: 0.16.0
> Environment: MacOS: 10.15.4 (Also happening on windows 10)
> Python: 3.7.3
> Pyarrow: 0.16.0
> Pandas: 0.25.3
> Reporter: Kevin Glasson
> Assignee: Wes McKinney
> Priority: Minor
> Fix For: 1.0.0
>
>
> When calling pa.Table.from_pandas() the code path that uses the ThreadPoolExecutor in dataframe_to_arrays (called by Table.from_pandas) the conversion is much much slower.
>
> I have a simple example - but the time difference is much worse with a real table.
>
> {code:java}
> Python 3.7.3 | packaged by conda-forge | (default, Dec 6 2019, 08:54:18)
> Type 'copyright', 'credits' or 'license' for more information
> IPython 7.13.0 – An enhanced Interactive Python. Type '?' for help.
> In [1]: import pyarrow as pa
> In [2]: import pandas as pd
> In [3]: df = pd.DataFrame({"A": [0] * 10000000})
> In [4]: %timeit table = pa.Table.from_pandas(df)
> 577 µs ± 15.3 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
> In [5]: %timeit table = pa.Table.from_pandas(df, nthreads=1)
> 106 µs ± 1.65 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
> {code}
>
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