2014年8月9日 · Note though the code generated depends on your compiler. In particular, when I compiled Duff's device using GCC targeting ARM architectures, the resulting ARM assembler was sub-optimal (I think GCC turned it into a jump table) at any optimization level. I ended up just handing coding the assembler.

What Duff's device does is implement this idea, in C, but (as you saw on the Wiki) with serial copies. What you're seeing above, with the unwound example, is 10 comparisons compared to 100 in the original - this amounts to a minor, but possibly significant, optimisation.

2012年1月12日 · Pedantically, no. Duff's Device was for writing to a hardware register (thus the target of the copy was always the same address). You can implement something very much like Duff's Device for a copy like this, but there will be a clarity and maintenance cost. I'd first profile to make sure it's a problem.

2017年1月20日 · Duff's device. In computer science, Duff's device is an optimized implementation of a serial copy that uses a technique widely applied in assembly language for loop unwinding. Its discovery is credited to Tom Duff in November of 1983, who …

2015年6月7日 · I would like to know what PorterDuff.Mode means in android graphics. I know that it is a transfer mode. I also know, that it has attributes such as DST_IN, Multiply etc.

2012年3月23日 · There are many different ways to compare branches, and it's depend on the specific use case you need. Many times you want to compare because something broken and you want to see what has been changes, then fix it, and see again what changed before commiting.

2009年1月2日 · Explains the difference between LEFT JOIN and LEFT OUTER JOIN in SQL Server.

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NOTE: When I first spent time reading about REST, idempotence was a confusing concept to try to get right.I still didn't get it quite right in my original answer, as further comments (and Jason Hoetger's answer) have shown.

2011年5月15日 · What is the meaning of this regex? [a-zA-Z]|\\d I know that [a-zA-Z] means all of a to Z chars but whats the mean of \\d?