Re: [boost] [Block Pointer] benchmark

Subject: Re: [boost] [Block Pointer] benchmark
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2011-05-25 19:15:08

Phil Bouchard <philippe_at_[hidden]> wrote:
> On 5/25/2011 3:27 PM, Nevin Liber wrote:
>>
>> You have yet to explain why your make_auto is so much slower than new
>> directly.  It just isn't that expensive to copy one pointer and zero out
>> another.  I can't imagine what else your code can possibly be doing.  I
>> can't imagine how that can be more, let alone significantly more expensive
>> than a heap allocation.  Enlighten me.
>
> Well if you have a direct assignment coming from operator new then the 
> pointer can be transferred directly into a register.  If you have 
> temporary r-values to copy it into then the transfer will be done from 
> one memory location to another, but it won't be a fast as a 
> register-to-register transfer.

That effect should be immeasurably small, or eliminated entirely by the compiler.

I think you had better post your benchmark code.  There must surely be 
something else going on here.

Phil.