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document new default hwm value
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@@ -415,11 +415,11 b' assigned to an engine at a given time. This limit is set with the'
415 415 .. sourcecode:: python
416 416
417 417 # the most common choices are:
418 c.TaskSheduler.hwm = 0 # (minimal latency, default)
418 c.TaskSheduler.hwm = 0 # (minimal latency, default in IPython ≤ 0.12)
419 419 # or
420 c.TaskScheduler.hwm = 1 # (most-informed balancing)
420 c.TaskScheduler.hwm = 1 # (most-informed balancing, default in > 0.12)
421 421
422 The default is 0, or no-limit. That is, there is no limit to the number of
422 In IPython ≤ 0.12,the default is 0, or no-limit. That is, there is no limit to the number of
423 423 tasks that can be outstanding on a given engine. This greatly benefits the
424 424 latency of execution, because network traffic can be hidden behind computation.
425 425 However, this means that workload is assigned without knowledge of how long
@@ -429,6 +429,11 b' effect by setting hwm to a positive integer, 1 being maximum load-balancing (a'
429 429 task will never be waiting if there is an idle engine), and any larger number
430 430 being a compromise between load-balance and latency-hiding.
431 431
432 In practice, some users have been confused by having this optimization on by
433 default, and the default value has been changed to 1. This can be slower,
434 but has more obvious behavior and won't result in assigning too many tasks to
435 some engines in heterogeneous cases.
436
432 437
433 438 Pure ZMQ Scheduler
434 439 ------------------
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