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From: ronald@robobar.co.uk (Ronald S H Khoo)
Newsgroups: news.software.b
Subject: C News sort -u | batcher ?
Summary: just a few thoughts
Message-ID: <1990Sep25.233128.10037@robobar.co.uk>
Date: 25 Sep 90 23:31:28 GMT
Sender: ronald@robobar.co.uk (Ronald S H Khoo)
Organization: Robobar Ltd., Perivale, Middx., ENGLAND.
Lines: 33

A while back, Henry suggested that the input to batcher might
be put through sort -u to remove duplicates caused by certain
types of sys file constructions involving multiple entries
(which I had asked about after stl!dww had pointed out certain
 advantageous tricks you could do with them).

I forgot about all this until I (finally :-) got round to reading the
C News paper this afternoon and realised, of course, that batcher does
actually gain from having sorted input.  You might not recover all of
the cost of doing the sort, but you certainly get some of it back.

The figures are too coarse using /bin/time and the disc subsystem on a
PC is rubbish -- but for a few of today's 400k batches the cost of
batcher is something like 2.5 to 3 seconds system, virtually zero user
and 25 elapsed (you see what I mean about PC discs ? :-() The sort costs
about 0.3 u+s and the saving in batcher seems to be not far from that.

[ In looking at this, I noticed that batcher won't read stdin, which
 is a shame though the extra cost of 'rm $tempfile' doesn't seem to
 be particularly significant ]

Unfortunately, these back of the envelope "measurements" on a few of
today's togo.* are rather buried in the noise level, but someone who
might have held back from putting in the sort for cost reasons might
now be less unwilling.

I thouroughly recommend the C news paper to any C News admin.  It was an
excellent read.  Perhaps there should be a louder pointer to it in the C
News distribution ? I couldn't find one there at all!
-- 
   ronald@robobar.co.uk | +44 81 991 1142 (O) | +44 71 229 7741 (H) | YELL!
   "Nothing sucks like a VAX"   --   confirmed after recent radiator burst!
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