dolfin team mailing list archive

[Marco Morandini <morandini@xxxxxxxxxxxxxx>]

On 03/01/2012 04:51 PM, Andy Ray Terrel wrote:
> On Thu, Mar 1, 2012 at 2:22 AM, Marco Morandini<morandini@xxxxxxxxxxxxxx>wrote:
>
> > There are some occurrences of
> >
> > container.size() == 0
> >
> > scattered throughout the code
> > (and fewer of container.size() != 0) .
> > Many of them are harmless, i.e. whenever container
> > is a vector. Some of them, however,
> > are for maps of sets (e.g. dolfin/adaptivity/**Extrapolation.cpp:149 ),
> > leading to completely unnecessary O(N) operations (racall that size() is
> > O(N) for a map or a list).
> While true for a list, it is not a problem for maps or sets:
>
> http://www.cplusplus.com/reference/stl/map/size/
> http://www.cplusplus.com/reference/stl/set/size/

I stand corrected

> While a silly implementation of a list will be O(n) most good
> implementations keep its size around.

but please be aware that the "silly implementation" we are talking about 
is gcc's one:

http://gcc.gnu.org/onlinedocs/libstdc++/manual/containers.html#sequences.list.size

Marco