Good afternoon all,
Having this seemingly well written routine in C, I wrote it's equivalent in
J, wishing to estimate the penalty for using J.
I am amazed and a bit mystified to find J nearly twice as fast: on this
Acer One with Gentoo Linux.
- C test: 2.0 secs
- J first test 1.13 secs
- J second test: 0.71 secs
>From a 38 Meg file, find all diff rent IP addresses following a given
label. In this test the number of addresses is about 16000, the required
different addresses is 7.
Attached is the C routine, and a 20K sample of the 38 meg data file.
Is the J use of mapped files the trick in favor of J? In C the entire file
is scanned, byte by byte.*
J routine:*
require'jmf'
require'files dir'
find=: 4 : 0
NB. x is the label preceding the IP adress,
NB. y is the file name
NB. produces a list of different IP adresses.
deb=. 6!:1 ''
JCHAR map_jmf_ 'file';y
nos=. I. x E. file
n=:(nos+/(0{$x)+i.16){file
unmapall_jmf_ ''
a=.'time in secs to read 38 megs, find IP adrs. etc. ',6j2":secs=. (6!:1
'')-deb
a=.a,:'diffreent IP adresses'
a,~.((n i."1 (' ')){."0 1 (n))
)
findTxt=: 3 : 0
NB. for testing find.
fn=:'/media/KINGSTON/logParse/messages.2'
NB.fn=:'G:\logParse\messages.2'
txt =.' rhost='
txt find fn
)
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