lianjian

Hi:
Here is a double array and its initialization:

// Method I
vector<vector<int> > p; // [numobjs][numnodes]
for(int i=0;i<numobjs;i++)
{
vector<int> q(numnodes);
p.push_back(q);
}

Usually, numnodes will be very large. Will this initialization be
very time-consuming? If so, I have to use something like:

// Method II
vector<vector<int> *) p;
for(int i=0;i<numobjs;i++)
{
vector<int> *q = new vector<int>(numnodes);
p.push_back(q);
}

If Method I is not that time-consuming, I prefer it because it is
intuitively straightforward.

Thanks for your help.

Regards

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bo persson

"vizlab" <lianjian@caip.rutgers.edu> skrev i meddelandet
news:f406ff9.0307051102.27baf6b7@posting.google.co m...


There is no use in allocating the vector object dynamically, becase it
is just a small book keeping object. The storage for its content will
be dynamically allocated anyway.

Method III is to tell the vector exactly what you want, and let it do
the initialization. I believe this creates fewer temporary objects, as
the same empty row is copied to all the others:


vector<vector<int> > p(numobjs, vector<int>(numnodes));


Bo Persson
bop2@telia.com

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