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Re: Problems with releasing memory for the "vector"!
- From: Christopher Jefferson <caj at cs dot york dot ac dot uk>
- To: h dot xia at sheffield dot ac dot uk
- Cc: libstdc++ <libstdc++ at gcc dot gnu dot org>
- Date: Wed, 20 Apr 2005 11:36:55 +0100
- Subject: Re: Problems with releasing memory for the "vector"!
- References: <1113958272.4265a780dfca7@webmail.shef.ac.uk>
Hao Xia wrote:
Hi, guys
I think the best way is to attach a test program, atest.cpp.
I was releasing memory from a nested vector:
vector< vector<someclass> > F;
But never get it done...
<snip>
As you can see, memory was not released even for non-existing variable.
Any comments?
This is just how memory allocation works.. the memory is kept in an
internal cache, so it can be given back out without having to go and ask
the operating system for some more memory.
Try altering your program to have the code in main twice. I did this,
and got this output:
RSS VSZ %MEM COMMAND
121780 156868 15.5 ./a.out
Before clear --------------------------
RSS VSZ %MEM COMMAND
109552 144708 13.9 ./a.out
After clear ---------------------------
RSS VSZ %MEM COMMAND
121840 156996 15.5 ./a.out
Before clear --------------------------
RSS VSZ %MEM COMMAND
109552 144708 13.9 ./a.out
After clear ---------------------------
as you can see, modulo some very small differences, the memory is being
reused the second time through.
I'm unsure if it is possible to force the memory to be released back to
the operating system, and how useful such a thing would be anyway...
Chris