in reply to Re: printing every 2nd entry in a list backwards (updated)
in thread printing every 2nd entry in a list backwards

Thank you kindly for your reply.

Your first solution is indeed exuding the knowledge of a monk, sadly it is rather slow.

Your second solution is actually what I tried first but it is also slower than my current solution. I am explicitly looking for a fast solution to beat the solution written in the language that also starts with "P" and must not be named.

I apologize for not being clear in the first place.

  • Comment on Re^2: printing every 2nd entry in a list backwards

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Re^3: printing every 2nd entry in a list backwards
by haukex (Archbishop) on May 19, 2017 at 12:43 UTC
    Your second solution is actually what I tried first but it is also slower than my current solution.

    How exactly did you measure this - code, sample input, etc.? Because at least under the following conditions, my code suggestion appears to be faster than yours. (Note I inserted use warnings; use strict; at the top of my script.)

    $ perl -wMstrict -le 'print join(" ",map {int(rand(100))-50} 0..rand(7
+)+3) for 1..1000000' >in.txt
$ wc -l in.txt 
1000000 in.txt
$ head -5 in.txt 
-49 43 0 -35 0 -20 -49 5 46 -11
-14 39 39 -24 -49 36 -7 -36 -43
15 30 5 -4 11
37 -25 27 -49 21
49 33 -15 -16 17 10 32 -14 -30
$ time perl 1190600.pl in.txt >out.txt

real    0m1.869s
user    0m1.863s
sys    0m0.004s
$ time perl 1190602.pl in.txt >out.txt

real    0m1.539s
user    0m1.521s
sys    0m0.016s

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      Apologies for not mentioning how I measure performance, please refer to my other reply for more information

[reply]

        From this node:

        by creating a file with 1_000_000 entries, each line having 10 numbers and then running the script against it

        I still can't reproduce your evidence.

        $ perl -wMstrict -le 'print join(" ",map {int(rand(100))-50} 1..10) fo
+r 1..1000000' >in.txt
$ time python list.py in.txt >pyout.txt

real    0m1.964s
user    0m1.934s
sys    0m0.028s
$ time perl 1190602.pl in.txt >out2.txt

real    0m1.953s
user    0m1.921s
sys    0m0.028s

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