[Fwd: too much copy in map]

[Jeremy G. Siek]

Levente Farkas wrote:
> 
> "Jeremy G. Siek" wrote:
> >
> > And BTW, the !spam thing in your return address is annoying.
> 
> what's more annoying when the email collecting robots find my email
> address and than send me spam. anyway if you are using a good mailer
> than it's not a problem since my Reply-to: is set to the correct
> address and if you press reply the good address will punt into the
> To: line.

Your previous emails did not have a Reply-to: line.

> I thing it's better to optimize code by hand if possible.

Try timing it with optimization turned on.

> anyway your example is wrong. you can't set v.first, since it's
> a const int and that's the reason (since pair has no constructor
> which inicialize just, the first) why we have to call to copy in

Good point.

> the this implementation. but operator[] can be implement without
> this extra copy, without hurt the standard (but the other insert
> can't).
> 
> > probably shouldn't put a large object directly into the map... instead
> > store pointers in the map and define a custom compare operator.
> 
> I thing the best way to avoid all memory management in a code, but
> (unfortunately) in this case stl always copy (sometimes more than
> necessary).

How about putting the objects in a vector (and pointers or indices
into the vector in the map). Of course you may find this indirection
causes more slow down than the extra copy.

-- 
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 Jeremy Siek                        email: jsiek@engr.sgi.com
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