billiard.Pool slower than multiprocessing.Pool

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
numpy, pandas, python
Domain
backend, performance

Research direction

Start by running the reported benchmark comparing billiard.Pool with multiprocessing.Pool on the pandas and numpy workload shown in the issue. Trace the source of the slowdown and document or fix the discrepancy; done means the comparison is explained or corrected while the resulting data still matches.

Written by the indexing model from the issue text.

Description

import pandas as pd
import time
import numpy as np


def aa(df):
    df_c = df.copy()
    df_c['C'] = df_c['A'] + df_c['B']
    return df_c


def using_multiprocessing(df, func, n_cores=4):
    from multiprocessing import Pool
    df_split = np.array_split(df, n_cores)

    pool = Pool(n_cores)
    start_time = time.time()
    df = pd.concat(pool.map(func, df_split))
    pool.close()
    pool.join()
    print(f"Using multiprocessing {time.time() - start_time}")
    return df


def using_billiard(df, func, n_cores=4):
    import billiard
    df_split = np.array_split(df, n_cores)

    pool = billiard.Pool(n_cores)
    start_time = time.time()
    df = pd.concat(pool.map(func, df_split))
    pool.close()
    pool.join()
    print(f"Using billiard {time.time() - start_time}")
    return df


inp = pd.DataFrame(np.random.randint(0,1000000,size=(1000000, 2)), columns=list('AB'))

df_1 = using_multiprocessing(inp, aa, 5)
df_2 = using_billiard(inp, aa, 5)

print(df_1.equals(df_2))

I got output:

Using multiprocessing 0.2115309238433838
Using billiard 31.323524951934814
True
Dominant language
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Forks
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Avg merge
4d 19h
Merged PRs (30d)
5

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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