Am 01.06.2013 20:23, schrieb Mehrdad:
On Saturday, 1 June 2013 at 16:30:05 UTC, David Piepgrass wrote:
David Piepgrass:
In fact, most STL algorithms require exactly two iterators--a
range--and none require only a single iterator<
I think there are some C++ data structures that store many single
iterators. If you instead store ranges you double the data amount.
Hashmaps would be the most common example. Usually implemented as a
linked list of key-value pairs along with a vector of list iterators.
In theory. But the .NET hashtables are implemented with an *array* of
key-value pairs and an array of *indexes*. The former forms a virtual
linked list that is more efficient than a traditional linked list, and
the latter is more efficient than a vector of iterators (especially on
x64, as the indexes can be 32-bit.)
Iterators are usually (but not always) faster, as they don't have an
extra level of indirection involved -- the iterators tell you directly
where to look in memory, whereas indices are useless without containers
(or iterators) backing them.
You shouldn't be using 32-bit indices on x64, that defeats the whole
point of x64.
As of .NET 4.5, 64bit array indexes are supported as well.
http://msdn.microsoft.com/en-us/library/hh285054.aspx
