Re: [Boost-users] Container iteration macro that is equivalent to handcoded iteration?

From: Mike Marchywka (marchywka_at_[hidden])
Date: 2007-10-11 21:06:44

>No we do not. The compiler does not need to know the contents of f to
>generate that code. Neither do we need to know the contents of f to
>discuss the code that the compiler generates in this case. I
>deliberately left f undefined so that loop efficiency can be studied in
>isolation.

If you don't write something the compiler could inline,I wouldn't
worry about things that are on the order of a subroutine call. If you put 
something
specific there, then the compiler has lots of options. Again, for very 
simple things
you could inline yourself, for more complicated things, in almost every case
I've written, memory access patterns dominate performance. A few cache 
misses can
kill you. Intel had some good references, you can skim their site for
recent stuff:
http://www.google.com/search?hl=en&q=ia32+performance+optimization+site%3Aintel.com

Anyone have a recent Intel compiler? I know in one case I had some hand 
written
SSE code with real clever register usage specialized for a certain wavelet 
transform.
As I recall, the naively written general c++ code executed in about the same 
time-
I don't remember specifically why, but most of the Vtune results, IIRC, 
pointed
to memory limits and not instruction count.

>From: Erik <sigra_at_[hidden]>
>Reply-To: boost-users_at_[hidden]
>To: boost-users_at_[hidden]
>Subject: Re: [Boost-users] Container iteration macro that is equivalent to 
>handcoded iteration?
>Date: Fri, 12 Oct 2007 01:10:07 +0200
>
>

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