dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

On 1 March 2012 16:23, Andy Ray Terrel <andy.terrel@xxxxxxxxx> wrote:
>
>
> On Thu, Mar 1, 2012 at 9:59 AM, Marco Morandini <morandini@xxxxxxxxxxxxxx>
> wrote:
>>
>> 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
>
>
> Yet another reason I hate gcc.  Anywho the foo.empty() is better anyway as
> it does represent the idea.
>

Yes, I agree that if conveys the intention better.

Garth

> -- Andy
>
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