[New-bugs-announce] [issue26374] concurrent_futures Executor.map semantics better specified in docs

[F.D. Sacerdoti]

New submission from F.D. Sacerdoti:

Hello,

My colleague and I have both written parallel executors for the concurrent_futures module, and are having an argument, as described in the dialog below. To resolve, I would like to add "order of results is undefined" to disambiguate the docs for "map(func, *iterables, timeout=None)".

DISCUSSION

Q: Correct Semantics to return results out of order?
JH: No, breaks API as stated
Rebut: order is undefined, concurrent_futures specifies map() returns an iterator, where builtin map returns a list. 
Q: Does it break the spirit of the module?
A: No, I believe one of the best things about doing things async is the dataflow model: do the next thing as soon as its inputs are ready.
 Q: Should we hold up the caller in all cases when there are stragglers, i.e. elements that compute slower?
 A: No, the interface should allow both modes.

def james_map(exe, fn, *args):
  return iter( sorted( list( exe.map( fn, *args ) ) ) )

----------
messages: 260396
nosy: F.D. Sacerdoti
priority: normal
severity: normal
status: open
title: concurrent_futures Executor.map semantics better specified in docs
type: enhancement
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue26374>
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