Xref: utzoo comp.bugs.4bsd:1735 comp.lang.c:35819
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!uunet!unisoft!greywolf
From: greywolf@unisoft.UUCP (The Grey Wolf)
Newsgroups: comp.bugs.4bsd,comp.lang.c
Subject: Re: Complexity of reallocating storage (was users command crap)
Message-ID: <3340@unisoft.UUCP>
Date: 5 Feb 91 20:55:40 GMT
References: <6662@exodus.Eng.Sun.COM> <15325:Jan2903:19:4991@kramden.acf.nyu.edu> <21548@yunexus.YorkU.CA> <5883:Feb102:05:4991@kramden.acf.nyu.edu>
Reply-To: greywolf@unisoft.UUCP (The Grey Wolf)
Organization: Foo Bar and Grill
Lines: 32

In article <5883:Feb102:05:4991@kramden.acf.nyu.edu> brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes:
>
>To rephrase: You don't seem to know what good programming techniques
>are. Tradeoffs between speed, space, and human effort are important.
>Tradeoffs between ``multiple passes'' and ``single pass'' are entirely
>irrelevant when they aren't reflected in speed, space, or human effort.

As I'm sure someone will/has pointed out already (haven't seen it yet, but
then news has strange timing problems), multiple-pass contemplation of
a file is stable IFF the file is guaranteed not to be physically rearranged
between passes.  (Of course the same can be said of a single pass thru
a file, but the window is (usually) *much* smaller).  Examples where
multiple passes work is on (normally) stable files, such as running them
thru a compiler or running a disk thru fsck.  (Of course, even there,
anomalies happen...)

Side issue: -- has anyone managed a single-pass fsck?  That would
be tricky at best, possibly disastrous.  I thought for a moment that
instead of doing five passes, one could use five file descriptors to
handle each phase, seeing as the size of a disk partition is effectively
fixed (last I checked, anyway...).  But I guess the passes need to
happen in a particular order...

>
>---Dan


-- 
thought:  I ain't so damb dumn!	| Your brand new kernel just dump core on you
war: Invalid argument		| And fsck can't find root inode 2
				| Don't worry -- be happy...
...!{ucbvax,acad,uunet,amdahl,pyramid}!unisoft!greywolf