Re: Slow manual 'garbage collection' in C++ ??

"Bo Persson" <>
Wed, 18 Jun 2008 19:14:01 +0200
<> wrote:

Well, after some hours of programming I changed my implementation is even slower right now !!

What did I do:
1) All the Point objects in my Hashtable now have 4 fields and the
coordinates are now Vectors instead of int* coordinates. Moreover de
destructor is empty now:

            using namespace std;
            class nDimPoint2
            { public:
                   vector<int> coordinates;
                   double valueReal;
                   double valueImag;
                   long code;
                  nDimPoint2(vector<int> _coordinates, double
_valueReal, double _valueImag, int useless);

This is passing a vector<int> by value. That is very unusual.


2) My Hasttable before was structured as:
vector<vector<nDimPoint2*> > myHashTable2;
but now it is a vector<vector<nDimPoint2> > myHashTable2;
There are no NEW or DELETE statements anymore in my programm.

But now my program is even slower than before. Again calling clear()
on all the vectors of the vector of my Hashtable takes a lot of
time. Some timings:

old implementation with clearing the Hashtable: 15 seconds,
old implementation without clearing the Hashtable: 8 seconds
(memory leak!!),
new implementation with clearing the Hashtable: 46 seconds,
new implementation without clearing the Hashtable: 14 seconds
(memory leak!!) for each 1000 iterations.

Horrible ! I'm asking myself why does it get even slowwer now !?!?
I'm was not such a bad programmer before ! :)

I made a profile report of the function calls and timings with my
Visual C++ 6.0

Oh dear!

This is a compiler from the previous millennium. Not what I would use
for high performance code.

I would almost think that the whole design of my implementation is
Any suggestions ??

Bo Persson

Bo Persson

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