Re: Change to search_n

[Paolo Carlini <pcarlini at suse dot de>]

Dimitris Xochellis wrote:

> I would recommend to first concentrate on improving
> the "generic" performance of your core algorithm and
> test it intensively. Then test it again with a variety
> of iterators, a variety data types and a variety of
> data distributions. Compare it a lot with my
> implementation. You can download my performance tests
> from CodeProject and use them to compare the two
> algorithms.
>
> After ensuring that your core algorithm is at least as
> fast as mine (there is no sense in re-implementing a
> slower version of a piece of free code that already
> exists!) then (and only then) is the time to worry
> about backward prefetchers in "exotic" targets and do
> specializations for N=2, N=3, N=4 etc. In my opinion,
> it is essential that you first work a lot more with
> your generic/core algorithm.
>  
Thanks Dimitri for your interesting feedback.

I feel compelled to point out two things:
1- Personally, as a maintainer of libstdc++-v3, I have nothing against 
you and Chris merging and submitting your work together. Nobody decided 
that Chris implementation was better than yours, or something like that. 
Simply, you did *not* show up on the list, whereas Chris did! Is this 
clear? Why don't you file a Copyright Assignment and start contributing 
first person to the project, I wonder?!?
2- About "backward prefetchers" and all that, those are concerns which 
are generally valid - that is, both for your and Chris implementations, 
of course - and *in principle* are critical concerns, that *in 
principle* can fundamentally undermine the relevance of this entire 
class of algorithms for a portable implementation.

Reading your message, together with very interesting technical remarks, 
I read between the lines that 1- and 2- above are not at all obvious to 
you. I may be wrong, of course...

Paolo.