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How can I get the memory size from a stl map container?

Posted on 2001-09-17
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Last Modified: 2012-06-27
friends, please help me on the following :-

#include <map>
#include <string>
using namespace std;

typedef map<string, int> STR_MAP;

int main(int argc, char* argv[])
{
  STR_MAP strmap;
  for(int i=0; i <1000; i++) {
    strmap.insert(STR_MAP::value_type(string  
               ("something"), i));
        }

/// i would like to get the memory allocated size of this
// map container
   // mem_size(strmap) ????????/


}
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Question by:pphari
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7 Comments
 
LVL 30

Expert Comment

by:Axter
ID: 6489102
Because std::string does not have a fix size, you would have to iterate through the list, to get the complete size.
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LVL 30

Expert Comment

by:Axter
ID: 6489122
You can use the following method to get the accumulate() function to get the total size:

Example code:

#include <map>
#include <string>
#include <numeric>

using namespace std;

typedef map<string, int> STR_MAP;

int GetTotalSize(int Accum, pair<string, int> Cur)
{
     return Accum + Cur.first.size() + sizeof(Cur.second);
}

int main(int argc, char* argv[])
{
     STR_MAP strmap;
     for(int i=0; i <1000; i++)
     {
          strmap.insert(STR_MAP::value_type(string  
               ("something"), i));
     }

     int TotalStringSize = accumulate(strmap.begin(),strmap.end(),0,GetTotalSize);
     
     return 0;
}

0
 
LVL 30

Expert Comment

by:Axter
ID: 6489125
The above code will return a number of 13, because you only have one item in the container.
Even though you add this (string("something"), i) to the container a 1000 times, you still only end up with one item because the key is the string.  Since the string remains the same, you're inserting the item in the same location over and over again.
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LVL 30

Accepted Solution

by:
Axter earned 100 total points
ID: 6489137
In the following example, I reversed the map pair to <int, string>.
This allows your code to insert 1000 items.

#include <map>
#include <string>
#include <numeric>

using namespace std;

typedef map<int, string> STR_MAP;

int GetTotalSize(int Accum, pair<int, string> Cur)
{
     return Accum + sizeof(Cur.first) + Cur.second.size();
}

int main(int argc, char* argv[])
{
     STR_MAP strmap;
     for(int i=0; i <1000; i++)
     {
          strmap.insert(STR_MAP::value_type(i, string ("something")));
     }
     
     int TotalSizeOfAllItemsInContainer = accumulate(strmap.begin(),strmap.end(),0,GetTotalSize);
     int TotalQtyOfPairsInContainer = strmap.size();
     int TotalSizeOfPair = sizeof(pair<int, string>);
     
     int TotalSizeOfContainer = TotalSizeOfAllItemsInContainer +
                    (TotalQtyOfPairsInContainer * TotalSizeOfPair) +
                    sizeof(STR_MAP);
     return 0;
}

0
 

Author Comment

by:pphari
ID: 6489503
hi axter, thanks for your great answer, infact my hash key is string only, the value of its changes all the time and container is a multimap..
once again thanks...
Hari
0
 

Author Comment

by:pphari
ID: 6489504
hi axter, thanks for your great answer, infact my hash key is string only, the value of its changes all the time and container is a multimap..
once again thanks...
Hari
0
 

Author Comment

by:pphari
ID: 6489505
hi axter, thanks for your great answer, infact my hash key is string only, the value of its changes all the time and container is a multimap..
once again thanks...
Hari
0

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