Investigation: downsides of being generic and correct

[Dicebot]

On Thursday, 16 May 2013 at 13:48:45 UTC, Juan Manuel Cabo wrote:
> On Thursday, 16 May 2013 at 10:35:12 UTC, Dicebot wrote:
>> Want to bring into discussion people that are not on Google+. 
>> Samuel recently has posted there some simple experiments with 
>> bioinformatics and bad performance of Phobos-based snippet has 
>> surprised me.
>>
>> I did explore issue a bit and reported results in a blog post 
>> (snippets are really small and simple) : 
>> http://dicebot.blogspot.com/2013/05/short-performance-tuning-story.html
>>
>> One open question remains though - can D/Phobos do better 
>> here? Can some changes be done to Phobos functions in question 
>> to improve performance or creating bioinformatics-specialized 
>> library is only practical solution?
>
> I bet the problem is in readln. Currently, File.byLine() and 
> readln() are extremely slow, because they call fgetc() one char 
> at a time.

Both manual and naive phobos version use same readln approach, 
but former is more than 10x faster. It was my first guess too, 
but comparing to snippets have shown that this is not the issue 
this time.