Re: Generate random numbers with shuf

[Pádraig Brady]

On 07/05/2013 07:04 PM, Assaf Gordon wrote:
> Hello,
> 
> On 07/04/2013 05:40 PM, Pádraig Brady wrote:
>> On 07/04/2013 09:41 PM, Assaf Gordon wrote:
>>>
>>> Regarding old discussion here:
>>> http://lists.gnu.org/archive/html/coreutils/2011-02/msg00030.html
>>>
>>> Attached is a patch with adds "--repetition" option to shuf, enabling 
>>> random number generation with repetitions.
>>>
>>
>> I like this.
>> --repetition seems to be a very good interface too,
>> since it aligns with standard math nomenclature in regard to permutations.
>>
>> I'd prefer to generalize it though, to supporting stdin as well as -i.
> 
> Attached is an updated patch, supporting "--repetitions" with STDIN/FILE/-e 
> (using the naive implementation ATM).
> e.g.
>   $ shuf --repetitions --head-count=100 --echo Head Tail
> or
>   $ shuf -r -n100 -e Head Tail

Excellent thanks.

> But the code is getting a bit messy, I guess from evolving features over time.
> I'd like to re-organize it a bit, re-factor some functions and make the code 
> clearer - what do you think?
> it will make the code slightly more verbose (and slightly bigger), but 
> shouldn't change the running performance.

If you're getting your head around the code enough to refactor,
then it would be great if you could handle the TODO: item in shuf.c
That would handle a performance regression in the common case
with reservoir sampling, and would be a good fit for the
upcoming release, given its performance theme.

cheers,
Pádraig.