Where is this code not freeing memory ?

Thomas J. Gritzan · *nix forums Guru Wannabe Joined: 09 Oct 2005 Posts: 124

joosteto@gmail.com · *nix forums beginner Joined: 09 Jul 2006 Posts: 20

wolverine wrote:

Ah, there does seem to be real-non-freed memory:

jithoosin · *nix forums beginner Joined: 21 Jul 2006 Posts: 6

Hi
Let me first of all tell that this problem is not specific to a
compiler like gcc. It even comes in windows. So please dont regard the
question as off topic.

I am posting a code using stl. I viewed the memory for program
by giving top command
eg: top -d 0.2 -p 'pid'
The pid will be printed out by the program itself.

Now coming to the question. The code is supposed to take around (200000
* 100 * 4 bytes = 76MB) .The top command at halfway point (line 41)
showed around 80MB. Until now it is correct. But after this i start
deleting elements from vector one by one. Then the code is supposed to
take lesser memory. But the top command showed still 80MB.
Why is this ?

I then googled and read in
http://www-1.ibm.com/support/docview.wss?rs=994&context=SSSHAD&dc=DB520&uid=swg21160634&loc=en_US&cs=UTF-8&lang=en
that stl "caches" memory and they gave a work around for it. I tried in
the code. Even that is not working.

Let me tell that valgrind or purify is not showing any leak in the
code. I some how need to free
from stl the memory. Is there any way ? Could any one help me ? I need
a general solution
which is applicable for all stl containers.

The code:

#include <vector>
#include <map>
#include<algorithm>
#include<unistd.h>
#include<iostream>
using namespace std;

//typedef vector <int, __malloc_alloc_template<0> > typIntVec;
//typedef map <long, typIntVec, std::less<long>,
//__malloc_alloc_template<0> > typLongIntVecMap;
typedef vector <int> typIntVec;
typedef map <long, typIntVec> typLongIntVecMap;

int main ()
{
typLongIntVecMap tMap;

cout<<"PID IS:"<<getpid()<<endl;
sleep(2);

cout<<"BEGIN EXECUTION."<<flush;

typLongIntVecMap::iterator tMapItr;
for (long j=1; j<200000; j++)
{
typIntVec vec;

//inserting 100 elements into the vector
for(int i=0; i<100; i++)
{
vec.push_back(i);
}

//put the vector into the map
tMap[j] = vec;

//simply putting a sleep so that we could see the increase in memory
if(j % 40000 == 0)
{
cout<<"."<<flush;
sleep(1);
}
}

cout<<endl<<"MEM IN STABLE POSITION......."<<endl;
cout<<"NOW IT SHOULD DECREASE";
sleep(2);
for (long j=1; j<200000; j++)
{
//get back a reference to the vector inside the map
typIntVec& vecRef = tMap[j];

//delete every element inside the vector
for(int i=0; i<100; i++)
{
typIntVec::iterator itr =
find(vecRef.begin(), vecRef.end(), i);
if(itr != vecRef.end())
{
vecRef.erase(itr);
}
}

//sleeping simple so that we could see the decrease in memory
if(j % 40000 == 0)
{
cout<<"."<<flush;
sleep(1);
}
}

cout<<endl<<"MAP WITH NO ELEMENTS IS IN MEM NOW"<<endl;
sleep(2);
return 0;
}

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