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

completely dwarf the loop-control overhead? In production code, how many loops do we write with such trivial bodies that the loop-control overhead makes a measurable difference?

I was going to comment that cache and memory organiztion usually are most relevant to real performance but since you mention this, I have run into counter-examples. However, these usually can unroll so the loop penalty goes to zero :) Adding code size optimization request would presumably discourage a compiler from trying this.

From: Nat Goodspeed Reply-To: boost-users@lists.boost.org To: boost-users@lists.boost.org Subject: Re: [Boost-users] Container iteration macro that is equivalent to handcoded iteration? Date: Thu, 11 Oct 2007 12:48:21 -0400

Erik wrote:

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Andrew Holden skrev:

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Erik wrote:

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Unfortunately it does not look so good for BOOST_FOREACH after this modification. It will increase to 24 instructions, while the handcoded is still only 21.

Forgive me if this was answered in an earlier post, but how complex is the loop body, including the complexity of any functions it calls?

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The answer is available by executing the test script in my previous post and then running the diff command that I showed in that post: The size of the loop body increases from 6 to 7 instructions and the code before the loop increases with 2 instructions.

No, that's not what Andrew asked. He was asking: in a *real* loop in your real application, wouldn't the work being done by the loop completely dwarf the loop-control overhead? In production code, how many loops do we write with such trivial bodies that the loop-control overhead makes a measurable difference? _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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