Re: performance bug of `wc -m`

[Peng Yu]

$ wc --version
wc (GNU coreutils) 8.29
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Paul Rubin and David MacKenzie.
$ seq 1000000 | time wc -m
6888896
        2.69 real         2.52 user         0.03 sys
$ seq 1000000 | time ./wcm.py
6888896
        1.30 real         1.18 user         0.04 sys

On Sun, May 13, 2018 at 12:54 PM, Assaf Gordon <address@hidden> wrote:
> Hello,
>
> On Sun, May 13, 2018 at 09:05:47AM -0400, Peng Yu wrote:
>> I am on Mac not on Linux. On Linux, I can confirm that `wc -m` is much
>> faster than `wcm.py`.
>
> As a first step, please run "wc --version" to confirm you are using
> gnu coreutils' wc and not the macos native wc program.
>
>> Here is the output on Mac.
>>
>> $ seq 1000000 > num.txt
>> $ time wc -m < num.txt
>> 6888896
>>
>> real    0m2.751s
>> user    0m2.622s
>> sys    0m0.042s
>> $  time ./wcm.py < num.txt
>> 6888896
>>
>> real    0m1.401s
>> user    0m1.234s
>> sys    0m0.051s
>
> Assuming it is coreutils' wc, I suspect file caching still plays
> a significant role here.
>
> Can you try:
>
>    seq 1000000 | time wc -m
>    seq 1000000 | time ./wcm.py
>
> And report the timing ?
>
> regards,
>  - assaf



-- 
Regards,
Peng