[Boost-users] [MultiIndex] insert with and without position hint

[Igor R]

Hello,

For some reason, the "hinted" version of insert() returns just an
iterator, while the "unhinted" one returns pair:
std::pair<iterator,bool> insert(const value_type& x);
iterator insert(iterator position,const value_type& x);

I've got a container with 1 ordered unique index. From one hand, I
have to know whether the insertion was succesful, but from the other
hand, 99% of the objects are inserted in their natural ascending
order, so I use the hinted version:
container_.insert(container_.end(), newObj);
So my question is whether there's any performance benefit of the
"hinted" version in such case, or I can move to the simple one w/o any
performance loss?

Thanks.
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[Joaquin M Lopez Munoz]

Igor R <boost.lists <at> gmail.com> writes:

> For some reason, the "hinted" version of insert() returns just an
> iterator, while the "unhinted" one returns pair:
> std::pair<iterator,bool> insert(const value_type& x);
> iterator insert(iterator position,const value_type& x);

The only reson for this dissimilarity is that
standard (unique) associative containers are defined
the same way.

> I've got a container with 1 ordered unique index. From one hand, I
> have to know whether the insertion was succesful, but from the other
> hand, 99% of the objects are inserted in their natural ascending
> order, so I use the hinted version:
> container_.insert(container_.end(), newObj);
> So my question is whether there's any performance benefit of the
> "hinted" version in such case, or I can move to the simple one w/o any
> performance loss?

There should be a performance penalty associated
to not using hinted insertion (if you want to
know the impact of this penalty on your particular
app I suggest you do some profiling).

An easy and cheap way to know whether the insertion was
succesful is to check if size() has increased.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

[Igor R]

> An easy and cheap way to know whether the insertion was succesful is to check if size() has increased.

Thanks, that's what I'm doing now.
I just thought that maybe unhinted version first tries to insert an
element at the end anyway...