Re: [Boost-users] boost and memory allocations (signals and others)

From: Beman Dawes (bdawes_at_[hidden])
Date: 2004-12-16 17:19:04

At 09:17 AM 12/15/2004, Caleb Epstein wrote:
 >On Mon, 13 Dec 2004 09:01:01 -0800, Frank Maddin <frankmad_at_[hidden]> 

 >wrote:
 >
 >> We've been thinking about using certain boost functionality on a 
project.
 >
 >> We were trying to keep the number of allocations down.
 >
 >See the attached test program which makes the Hello class "noisy" and
 >runs two different versions of your signals test.  One uses object
 >copy semantics and the other uses reference semantics.  Compare the
 >output:
 >
 >copy test:
 >Hello::Hello () @ 0xbfffb950
 >Hello::Hello (const ref) @ 0xbfffb8c0
 >Hello::Hello (const ref) @ 0xbfffb870
 >Hello::Hello (const ref) @ 0xbfffb830
 >Hello::Hello (const ref) @ 0xbfffb7e0
 >Hello::Hello (const ref) @ 0x8050fb0
 >Hello::~Hello @ 0xbfffb7e0
 >Hello::~Hello @ 0xbfffb830
 >Hello::~Hello @ 0xbfffb870
 >Hello::~Hello @ 0xbfffb8c0
 >Hello::Hello (const ref) @ 0x8050fc0
 >Hello::Hello (const ref) @ 0x8050fc8
 >Hello::Hello (const ref) @ 0x8050fd0
 >Hello::~Hello @ 0x8050fc8
 >Hello::~Hello @ 0x8050fc0
 >Hello::~Hello @ 0x8050fb0
 >i = 1968
 >Hello::~Hello @ 0x8050fd0
 >Hello::~Hello @ 0xbfffb950
 >
 >ref test:
 >Hello::Hello () @ 0xbfffb950
 >i = 1968
 >Hello::~Hello @ 0xbfffb950

Wow! That is a pretty substantial difference.

Seems like the signals docs should make a point of explaining the 
efficiency gained by using ref. Or maybe they do, but I didn't find 
anything in several minutes of poking around the docs. There is no table of 
contents entry like "Efficiency considerations" or similar.

--Beman