[Development] Upgrading the sources to C++11 keywords (Q_NULLPTR, etc.)
mathias at taschenorakel.de
Sun Feb 8 22:28:06 CET 2015
Am 08.02.2015 um 14:28 schrieb Marc Mutz:
> c. Using QMap. As Alex Stepanov put it: every use of a map should be discussed
> in a face-to-face meeting with your manager. Since we don't have that, I'd
> change this to: Everyone wishing to use a QMap should implement one before
> using it for the first time. Then you'd see what you inflict on the world.
> In the vast majority of cases, a sorted vector is much faster, due to
> locality-of-reference. A RB-tree is optimized for wildly mixing insertions,
> lookups, and removals. When you can batch updates and separate them from
> lookups, time-wise, then a sorted vector is usually preferrable.
I totally agree, thank you for raising this. Sadly a sorted vector isn't
as convenient to use as a map. Maybe there should some convenience API
added, Or does it exist already and I am just too ignorant to know it?
> d. Algorithmic complexity. Avoid O(n²) like the plague. Anthing worse than
> that should get a big fat comment saying why it's necessary (like: this
> optimisation algorithm is equivalent to the knapsack problem, so I need to
> use this exponential algorithm, because a) we need the global optimum, not
> a local one, and b) the set is always less than four elements.
I wonder if one could do a clang plugin checking for the most obvious
complexity class sins. Like invocation of methods known to be O(n) from
within a lengthy loop. One really has to find a way to educate people
about those sins.
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