Creeping Bloat in Phobos

[via Digitalmars-d]

On Monday, 29 September 2014 at 14:25:34 UTC, monarch_dodra wrote:
> This just misses the *entire* familly of algorithms that 
> operate on generic types, such as "map". EG: the totality of 
> std.algorithm. Oops.

But if you know the common operations on strings used in many 
programs, then you want them to perform. So you need a mix of 
special cased precomputed lookup-tables and/or special cased SIMD 
instructions that will outperform a generic map() by a 
significant margin.

I am not arguing against generic apis being desirable, I am 
questioning of the feasibility of being competitive in the space 
of utf-8 strings without designing for SIMD.

Obviously, doing bitwise and 0x80808080...80 followed by a simd 
compare with "           " will beat anything scalar based if you 
want to test for a space in a utf-8 string.

Intel has made a real effort at making UTF-8 SIMD optimizable 
with the last few generations of instruction sets.

Figuring out how to tap into that potential is a lot more 
valuable than defining an api a priori. That means writing SIMD 
code and comparing it to what you have. If SIMD blows what you 
have out of the water, then it ain't god enough.

If you can define the string APIs to fit what SIMD is good at, 
then you are onto something that could be really good. D is in a 
position where you can do that. C++ aint.