Re: Memory issues with Map

LR <>
Fri, 04 Jan 2008 16:00:13 -0500
<477e9dcb$0$2952$> wrote:

I have written a program that loads a file having 3 columns into a
map. Here is the declaration:

struct strE
   char iEID[22+1];
   char acEN[6+1];
   int iDed;

map<string, struct strE> mEro;

                    struct strE eStr = {0,};
                    if ( 0 < vDataColumn.size() )
                        eStr.iDzReceived =
 //vDataColumn has columns from file which is "|" delimiter separated.
We split the line into columns and store it in vDataColumn

                                struct strERO>(key, eStr)

I am seeing that for 6MB file the resident memory is around 12 MB. It
looks like either there is a memory leak or limitation in Map. I am
not sure what kind of memory mangement is used by Map. Could somebody
shed some light as what would be the best approach and dos and donts
when dealing with Maps

Aside from the inconstancies that Victor pointed out in another post,
there are a few things that might be useful to know.

How many entries in the 6MB file.

You say that your file has three columns. What are they? I ask because
your struct strE (or strERO?) has three member variables and the key of
the map would make four values per entry. So if your data has three
values per entry and you're storing per entry (key and three others)
would that account for the change in size?

What types are the three values in the data file? And for each of the
'string' type values what is the largest, smallest, and average size?

Is it possible that you'd be better off rewriting your struct with
std::string instead of char arrays? Or perhaps writing some very
lightweight string class if memory usage is a big concern?

Also, what is sizeof(int) on your system and how many bits is a char?

I think given the information you've provided so far, it's difficult to
give a useful answer.


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