Errata for Parallel Programming with Microsoft® .NET
The errata list is a list of errors and their corrections that were found after the product was released.
The following errata were submitted by our customers and have not yet been approved or disproved by the author or editor. They solely represent the opinion of the customer.
Color Key: Serious technical mistake Minor technical mistake Language or formatting error Typo Question Note Update
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| Printed, PDF, ePub, Mobi, |
Page 121
Para 3 onwards |
jsh003guardz63 wrote Jul 19, 2011 at 8:15 AM
The explanation of performance characteristics of pipelines on p121 needs clarification and possibly correction.
In particular, ?If there are enough available cores and if all stages of a pipeline take an equal amount of time, the execution time for the pipeline as a whole is the same as the time for just one stage?, would appear to be incorrect.
If:
S = the number of stages in figure 4 (= 4)
N = the number of images in figure 4 (= 6)
T = the duration to process one stage for one image (= t1 - t0 = t2 ? t1)
Then:
The elapsed time for a completely parallel and completely efficient pipeline is (S+N-1) * T.
The elapsed time taken for one stage = N * T.
But:
(S+N-1) x T is only equal to N * T when S = 1.
If the sidebar on p121 is referring to the case where S = 1, the phrasing of that sidebar needs changing, as it currently implies that (S+N-1) x T = N * T for any S. If the sidebar isn't referring to the case where S = 1, it needs re-wording as its intended meaning is unclear and/or incorrect. Possibly, it's trying to say that each core has an equal execution time, but I don't think that's the intended meaning...
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Ade Miller
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Oct 18, 2012 |