legOS : 3147


Robotics / RCX / legOS / 3147	3146 \| 3148

Subject:	Re: command framing as seen from kernel/program.lrkey_handler
Newsgroups:	lugnet.robotics.rcx.legos
Date:	Sat, 1 Feb 2003 18:28:23 GMT
Viewed:	3857 times

"Pat LaVarre" <ppaatt@aol.com> wrote in message news:H9n64q.B2p@lugnet.com... > > > > ... brickos ... > > > Sorry to see the source less online than: http://lxr.linux.no/source/ > > > > Here's the link: > > http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/brickos/brickos/kernel/ > > Cool, thanks. No grep, right? I dunno, haven't found one yet, though. > > there's no fast way to execute > > log2() on the H8 (i.e. no O(1) solution) > > Mmmmm. I am curious, if that's ok. > > To get log2(xx) in O(1) time we could fetch (p[xx & -xx]) i.e. fetch our • choice > of the bytes at offset x 0 1 2 4 8 10 20 40 80 from some p we like. Touché. Yes, tables, overlooked that. > Merely standard C can't easily express that old idea without misleading • the > linker into wasting x81 - 9 bytes, which I gather would be considered • expensive > on an H8? I think that smaller code size is preferable to faster execution speed in this instance since this section of code would only get executed a few dozen or so times per second (and then only when one is using the remote). Mark

Message has 1 Reply:

		Re: command framing as seen from kernel/program.lrkey_handler
(...) Just to be more certain we're understanding each other, if that's ok, I'll mention that ... 1) Newbie that I am, I have no clue how frequently brickos switches on bit masks. I wonder if only to decode xD2 RemoteCommand. 2) Using log2(xx & -xx) (...) (22 years ago, 2-Feb-03, to lugnet.robotics.rcx.legos)

Message is in Reply To:

		Re: command framing as seen from kernel/program.lrkey_handler
(...) Mmmmm. I am curious, if that's ok. To get log2(xx) in O(1) time we could fetch (p[xx & -xx]) i.e. fetch our choice of the bytes at offset x 0 1 2 4 8 10 20 40 80 from some p we like. Merely standard C can't easily express that old idea without (...) (22 years ago, 1-Feb-03, to lugnet.robotics.rcx.legos)

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