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Are Exceptions in C++ really slow
...cattered around memory, and complex operations to run (basically a dynamic_cast test for each handler)
So, mostly cache misses, and thus not trivial compared to pure CPU code.
Note: for more details, read the TR18015 report, chapter 5.4 Exception Handling (pdf)
So, yes, exceptions are slow on th...
C++ performance challenge: integer to std::string conversion
...e method, such as different stringstream implementations or boost::lexical_cast. It does not, however, make sense when asking for new code, a specialized algorithm, to do this. The reason is that int2string will always involve heap allocation from std::string and if we are trying to squeeze the last...
Are HLists nothing more than a convoluted way of writing tuples?
... aren't typically that interesting (at least, they aren't unless they type cast internally). shapeless provides a form of polymorphic function value which allows the compiler to select type-specific cases in exactly the way you're doubtful about. For instance,
// size is a function from values of a...
When do we have to use copy constructors?
...structor with a correct signature and commit the sin of turning to a const_cast.
Copy-on-write (COW)
A COW container that has given away direct references to its internal data MUST be deep-copied at the time of construction, otherwise it may behave as a reference counting handle.
Though COW ...
How to find the kth smallest element in the union of two sorted arrays?
...; issorted(firstb, lastb, less));
for ( ; ; ) {
assert(n < static_cast<size_t>((lasta - firsta) + (lastb - firstb)));
if (firsta == lasta) return *(firstb + n);
if (firstb == lastb) return *(firsta + n);
size_t mida = (lasta - firsta) / 2;
size_t midb = (lastb - first...
Performance optimization strategies of last resort [closed]
... clear on a load op. Find places where floats, vectors, and ints are being cast to one another and eliminate them. Use __restrict liberally to promise the compiler about aliasing.
Microcoded operations. Most processors have some operations that cannot be pipelined, but instead run a tiny subroutine ...
What are rvalues, lvalues, xvalues, glvalues, and prvalues?
...be moved from
im: has identity and can be moved from (e.g. the result of casting an lvalue to a rvalue reference)
Im: does not have identity and can be moved from.
The fourth possibility, IM, (doesn’t have identity and cannot be moved) is not
useful in C++ (or, I think) in any other l...
Is gcc's __attribute__((packed)) / #pragma pack unsafe?
... blame the compiler for it's complacency though. While gcc does have a -Wcast-align option, it isn't enabled by default nor with -Wall or -Wextra. This is apparently due to gcc developers considering this type of code to be a brain-dead "abomination" unworthy of addressing -- understandable disda...
Java 8: Lambda-Streams, Filter by Method with Exception
...n method.get();
} catch (AdapterException e) {
throw x.cast(e.getCause());
}
}
@Override
public <A, R> R collect(Collector<T, A, R> collector) throws X {
return unmaskException(() -> delegate.collect(collector));
}
}
Then you coul...
How to get first and last day of previous month (with timestamp) in SQL Server
...
Not thinking CONVERT is the best solution if CAST is available
– Kennah
Jun 28 '19 at 19:29
...