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From: Bruce Adams [mailto:tortoise_74@yahoo.co.uk]
To: boost-users@lists.boost.org
Sent: Fri, 21 Sep 2007 10:24:58 -0600
Subject: [Boost-users] container performance on 64 bit systems


Hi,
This may seem slightly off topic initially but bear
with me. I have recently been having fun with the
ordinary STL containers on a 64bit linux system. In
particular the sorted associative containers set and
map bloat the memory usage to an unacceptable level.
Part of this is down to 64 bit pointers versus 32 bit
pointers.
In a standard Red-Black tree implementation each node
has 3 pointers, these double in size as do any
pointers in the containers themselves. There are also
issues with allocating on 8byte and 16byte boundaries.

I measured and discovered that an otherwise highly
efficient structure took *10* times as much memory on
a 64bit machine vs. the 32bit one. I can half the
memory usage for a std::set by replacing it with a
std::vector and sorting it manually. Nothing too out
of the ordinary there.
To solve my problem I have replaced a large number of
64bit pointers with indices and manipulate
std::vector's of these instead of using associative
containers.

Are there any 'better' implementations of std::set
etc. (preferably open source GNU/Linux compatible) out
there? Are any planned?
Does boost contain any suitable replacements?

Does boost itself suffer from or tackle this 64bit
bloat problem?

Regards,

Bruce.



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