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Doc/library/multiprocessing.rst
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@ -2440,6 +2440,16 @@ with the :class:`Pool` class.
the process pool as separate tasks. The (approximate) size of these the process pool as separate tasks. The (approximate) size of these
chunks can be specified by setting *chunksize* to a positive integer. chunks can be specified by setting *chunksize* to a positive integer.
It is important to distinguish between *maxtasksperchild* in the
:class:`Pool` class and *chunksize*. Whereas *maxtasksperchild* denotes
how many tasks can be run at once before those resources are freed,
*chunksize* defines how many separate chunks in which to split all of the
iterations of the function. In order for each iteration of the function to
be executed separately, *chunksize* needs to be set to 1.
Whereas :meth:`imap` defaults to a *chunksize* of 1, :meth:`map` defaults
to ``None`` and needs to be declared explicitly.
Note that it may cause high memory usage for very long iterables. Consider Note that it may cause high memory usage for very long iterables. Consider
using :meth:`imap` or :meth:`imap_unordered` with explicit *chunksize* using :meth:`imap` or :meth:`imap_unordered` with explicit *chunksize*
option for better efficiency. option for better efficiency.